Today's Message Index:
----------------------
1. 12:12 AM - Matronics List Fund Raiser Postponed During 2020... (Matt Dralle)
2. 12:59 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Todd Bartrim)
3. 01:02 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Todd Bartrim)
4. 05:47 AM - Re: Lead Acid Batteries (Robert L. Nuckolls, III)
5. 05:50 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Finn Lassen)
6. 06:17 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Robert L. Nuckolls, III)
7. 06:26 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Finn Lassen)
8. 06:30 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Robert L. Nuckolls, III)
9. 06:33 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Robert L. Nuckolls, III)
10. 07:01 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Finn Lassen)
11. 08:12 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Ernest Christley)
12. 09:07 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Robert L. Nuckolls, III)
13. 10:06 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Robert L. Nuckolls, III)
14. 10:54 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Finn Lassen)
15. 11:12 AM - Re: DIY LED landing light -- Wing skin as heat sink? (Finn Lassen)
16. 12:37 PM - Re: DIY LED landing light -- Wing skin as heat sink? (Charlie England)
17. 01:24 PM - Re: DIY LED landing light -- Wing skin as heat sink? (Ernest Christley)
18. 03:38 PM - Microair 760 transceivers for sale (Robert L. Nuckolls, III)
19. 03:40 PM - Re: Breaker then pump failure (Robert L. Nuckolls, III)
20. 03:44 PM - Re: DIY LED landing light -- Wing skin as heat sink? (Robert L. Nuckolls, III)
21. 04:00 PM - Re: DIY LED landing light -- Wing skin as heat sink? (Finn Lassen)
22. 04:41 PM - Re: DIY LED landing light -- Wing skin as heat sink? (Finn Lassen)
23. 04:53 PM - Re: ADS-B and Transponder antenna... (Eric Page)
24. 06:02 PM - Re: DIY LED landing light -- Wing skin as heat sink? (Charlie England)
25. 06:16 PM - Re: DIY LED landing light -- Wing skin as heat sink? (Ernest Christley)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Matronics List Fund Raiser Postponed During 2020... |
Dear Listers,
Normally, in November I hold a List Fund Raiser where I ask Listers to make a Contribution
to support the operation and upkeep of these List resources.
In light of the happenings during this 2020 season, I have decided to postpone
the Fund Raiser this year and encourage members to focus on their families and
personal needs.
I want to thank everyone that has supported the Lists in the past. Despite the
uncertain times we're experiencing right now, I want to assure everyone that
I fully intend to continue supporting the Lists as I always have; with no anticipated
degradation in service levels.
Happy Holidays to all my friends around the world!
Matt Dralle
Matronics List Manager
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
Hi Finn;
This may not be using the skin as a heat sink, but it works great and is
lightweight.
I bought some of these lights from Amazon and took them apart to make my
landing lights.
https://www.amazon.ca/Lightfox-Driving-Offroad-Waterproof-Warranty/dp/B01M9
8GWR2/ref=sr_1_2_sspa?crid=31MNRKKNOSJAA&dchild=1&keywords=led+spot
+lights+offroad&qid=1604214923&sprefix=led+spot+%2Caps%2C274&sr=8-2-s
pons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEySTdLUVhZSDFQQTEmZW5jcnlwdGV
kSWQ9QTA2NDM1NzcyUVdZV1QyR0tJS1dRJmVuY3J5cHRlZEFkSWQ9QTAwNzU1NTUzSzVRRTYzNT
ZSUjZHJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY
2s9dHJ1ZQ=
this is from Amazon's Canada site, but I'm sure you can find them even
cheaper on the US site.
Then I took them apart as you can see in these pictures posted here on
Google photos
https://photos.app.goo.gl/S68h3zpVy7RVJDTT8
I can't remember how much weight I discarded from the parts I removed, but
it was most of the weight of the light.
The mounting plate was originally part of the Duckworths landing light that
I wasted my money on. That is a simple part to make. I have 2 of those
mounted mid wing and are pointed down for use as taxi lights, then I
mounted 2 into the wingtips (required some fibreglass work) and have them
pointed straight ahead for landing lights.
These lights are very durable and bright. I must have bought more than a
dozen so far as I've put some on my truck, my son's Jeep, my skidsteer, 4
on the plane and probably the harshest duty is the pair I put on my ATV,
which are thoroughly abused. They are extremely bright in the bush with
very little current draw so my ATV has no problem running them
continuously. I think those ones are at least 4 years old and are still
working great despite the abuse.
It looks like there are even better versions of these lights now, that
appear to be the same construction so you can still dismantle them to get
the good parts only.
Todd Bartrim
RV9
13Bturbo
On Sat, Oct 31, 2020 at 8:20 PM Finn Lassen <finn.usa@gmail.com> wrote:
>
> Might say the most critical thing for LED life and high lumens output is
> conducting heat away from the LED.
>
> That usually means attaching heavy heat sinks.
>
> Could we save weight by using the wing skin as a heat sink?
>
> I understand it would present problems in adjusting (pointing) the light.
>
> But, could we bond/attach the LED to a (alum?) plate that is then
> bonded/riveted/screwed to the leading edge wing skin?
>
> Let's say we use a 100W LED (~13,000 lumens). We'd have to remove 70 to
> 80W of heat from the LED. LED doesn't like more than 150=C2=B0C and it wo
uld
> be better to keep it cooler. LED area 34x34mm.
>
> I don't have a good grasp of thermal conductivity (conductance?). How
> thick would the mount plate have to be? How much area would be needed
> where the mount plate contacts the wing skin (using some kind of heat
> sink compound/adhesive between the plate and skin)?
>
> Am I right in assuming the plate has to be thickest were the LED is
> mounted and then taper down in thickness as it expands out in width and
> height?
>
> Perhaps tapered layers of carbon fiber (with thermal epoxy) would be
> better as the LED mount plate? (After a diamond, graphene or graphite
> apparently has the best thermal conductivity.)
>
> Any (thermal) engineers here that could enlighten me?
>
> Finn
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
===========
===========
===========
===========
===========
>
>
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
Ooops, that was the link for my own collection of reference photos,
This is the one you need to see how I did the lights
https://photos.app.goo.gl/wQvyosNK1QBFjz7c8
Todd Bartrim
On Sun, Nov 1, 2020 at 12:54 AM Todd Bartrim <bartrim@gmail.com> wrote:
> Hi Finn;
> This may not be using the skin as a heat sink, but it works great and i
s
> lightweight.
> I bought some of these lights from Amazon and took them apart to make my
> landing lights.
>
> https://www.amazon.ca/Lightfox-Driving-Offroad-Waterproof-Warranty/dp/B01
M98GWR2/ref=sr_1_2_sspa?crid=31MNRKKNOSJAA&dchild=1&keywords=led+sp
ot+lights+offroad&qid=1604214923&sprefix=led+spot+%2Caps%2C274&sr=8-2
-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEySTdLUVhZSDFQQTEmZW5jcnlwd
GVkSWQ9QTA2NDM1NzcyUVdZV1QyR0tJS1dRJmVuY3J5cHRlZEFkSWQ9QTAwNzU1NTUzSzVRRTYz
NTZSUjZHJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2x
pY2s9dHJ1ZQ=
> this is from Amazon's Canada site, but I'm sure you can find them even
> cheaper on the US site.
> Then I took them apart as you can see in these pictures posted here on
> Google photos
> https://photos.app.goo.gl/S68h3zpVy7RVJDTT8
> I can't remember how much weight I discarded from the parts I removed, bu
t
> it was most of the weight of the light.
> The mounting plate was originally part of the Duckworths landing light
> that I wasted my money on. That is a simple part to make. I have 2 of tho
se
> mounted mid wing and are pointed down for use as taxi lights, then I
> mounted 2 into the wingtips (required some fibreglass work) and have them
> pointed straight ahead for landing lights.
> These lights are very durable and bright. I must have bought more than a
> dozen so far as I've put some on my truck, my son's Jeep, my skidsteer, 4
> on the plane and probably the harshest duty is the pair I put on my ATV,
> which are thoroughly abused. They are extremely bright in the bush with
> very little current draw so my ATV has no problem running them
> continuously. I think those ones are at least 4 years old and are still
> working great despite the abuse.
> It looks like there are even better versions of these lights now, that
> appear to be the same construction so you can still dismantle them to get
> the good parts only.
>
> Todd Bartrim
> RV9
> 13Bturbo
>
> On Sat, Oct 31, 2020 at 8:20 PM Finn Lassen <finn.usa@gmail.com> wrote:
>
>
>>
>> Might say the most critical thing for LED life and high lumens output is
>> conducting heat away from the LED.
>>
>> That usually means attaching heavy heat sinks.
>>
>> Could we save weight by using the wing skin as a heat sink?
>>
>> I understand it would present problems in adjusting (pointing) the light
.
>>
>> But, could we bond/attach the LED to a (alum?) plate that is then
>> bonded/riveted/screwed to the leading edge wing skin?
>>
>> Let's say we use a 100W LED (~13,000 lumens). We'd have to remove 70 to
>> 80W of heat from the LED. LED doesn't like more than 150=C2=B0C and it w
ould
>> be better to keep it cooler. LED area 34x34mm.
>>
>> I don't have a good grasp of thermal conductivity (conductance?). How
>> thick would the mount plate have to be? How much area would be needed
>> where the mount plate contacts the wing skin (using some kind of heat
>> sink compound/adhesive between the plate and skin)?
>>
>> Am I right in assuming the plate has to be thickest were the LED is
>> mounted and then taper down in thickness as it expands out in width and
>> height?
>>
>> Perhaps tapered layers of carbon fiber (with thermal epoxy) would be
>> better as the LED mount plate? (After a diamond, graphene or graphite
>> apparently has the best thermal conductivity.)
>>
>> Any (thermal) engineers here that could enlighten me?
>>
>> Finn
>>
>>
>> ---
>> This email has been checked for viruses by Avast antivirus software.
>> https://www.avast.com/antivirus
>>
===========
===========
===========
===========
===========
>>
>>
>>
>>
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Lead Acid Batteries |
>
>
>Second question is about allowing a lead acid
>battery to discharge all the way down to zero=85or
>if it had gotten severely discharged a few
>timmes=85it will no longer be serviceable.=C2 Is
>this accurate?=C2 If so why would a good battery
>become junk just because you =9Cleft the lights
>on=9D and drained it down to zero?
It's not a 'sudden death' phenomenon. In fact, to achieve
TSO qualification on aircraft batteries, one of the tests
is to completely discharge the battery, place a dead short
on it for a period of time (don't recall the interval off
top of my head) and the conduct a 'recovery charging protocol'.
But leaving a lead-acid battery in a discharged state
accelerates corrosion of the positive plate which
ultimately trashes the battery.
>Third question is what is the difference between
>a =9Ccar battery=9D and a =9Cmarine battery/ deep cycle
battery=9D?
Here's an excellent article that speaks to that
topic . . . among others.
https://tinyurl.com/y69ltgh6
By the way, there's a constellation of excellent
articles on the characteristics and maintenance
of various battery chemistries on this website:
https://tinyurl.com/yalty6y7
Bob . . .
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
That would introduce drag.
Name of the game here is no drag and lowest possible weight for max
light output (lumens) directed in a narrow beam that can reach 3,000
feet or more down a deer infested runway.
If it wasn't for needing the reflector to concentrate the light in a
beam, we could simply mount the LED chip flush with the wing skin, using
an alum backing plate (about the thickness of the one the LED chips
comes bonded to, I guess) and the wing skin would be a perfect heat sink.
My thermodynamic question comes into play as we move the LED chip
further back from the leading edge wing skin. Surely someone has
experience in designing heat sinks and what's required in terms of
conducting the heat from the point where a chip is mounted and out into
the fins exposed to air. Hopefully the thousands of heat sink design you
see are not all the result of trial and error. There must be some
physics (thermodynamics?) behind it.
Finn
On 11/1/2020 1:38 AM, Charles Davis wrote:
> <charlesdavis@iuncapped.co.za>
>
> How about ducting some of the slip-stream directly onto the heat-sink,
> you could then use a MUCH smaller/lighter sink than relying on ambient
> air inside the fitting
>
>
> On 01/11/20 05:08 am, Finn Lassen wrote:
>> <finn.usa@gmail.com>
>>
>> Might say the most critical thing for LED life and high lumens output
>> is conducting heat away from the LED.
>>
>> That usually means attaching heavy heat sinks.
>>
>> Could we save weight by using the wing skin as a heat sink?
>>
>>
>
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
>
>Let's say we use a 100W LED (~13,000 lumens).
>We'd have to remove 70 to 80W of heat from the LED.
>LED doesn't like more than 150=C2=B0C and it would
>be better to keep it cooler. LED area 34x34mm.
Don't think it's quite that bad. LED efficiency is on the order of
35 to 40% which would dump 60 to 65 watts of heat.
>I don't have a good grasp of thermal
>conductivity (conductance?). How thick would the mount
>plate have to be? How much area would be needed
>where the mount plate contacts the wing
>skin (using some kind of heat sink
>compound/adhesive between the plate and skin)?
The flow of heat energy is analogous to the flow
of electrical energy. Temperature rise is 'Volts'.
Thermal resistance is 'Ohms' and Watts is still
watts. Configuring thermal management for an
LED is identical to that of say a power transistor.
The working part of the LED has a known thermal
resistance between the semiconductor junction
and the heat sinking surface or case. It can
be stated in degrees C per watt. So if you
have a junction dissipating 100 watts of heat
and it's packaged thermal resistance is say
1C/W then the junction is going to operate
at 100C HIGHER than the heat sinking surface.
If the thing is limited to 150C then you have
to maintain the case at 50C.
There will be a thermal resistance associated
with the mounting of the device to the
heat sink . . . add say 0.25C/W. Adding up
the resistances we're at 1.25C/W . . . 100
Watts will drop 125C so now your heatsink
has to operate at 25C.
These resistance numbers are pulled out of
my hat . . . but you get the picture.
Now we get to the proposed 'heat sink'. Just
how good is it. VERY difficult to calculate
if complex like structure of an airplane.
Best way to test it is bolt a power resistor
to the LED mounting surface and cause it
to dissipate X watts. Thermocouple the area
under the resistor to get degrees C/Watt
of thermal resistance.
Now to throw a really big monkey wrench into
the study. AIR FLOW has a PROFOUND influence
on thermal resistance. Those tiny chips in
your computer dissipate a bucket load of heat
in terms of their mass. The heat sink on your
CPU has lots of SURFACE area and a FAN.
The only time your LED nav lights are at
risk for thermal abuse is while sitting
on the ground or taxi. If I were designing
an LED fixture, I'd probably include
over temperature sensing to dim the lighting
to prevent thermal damage. Once airborne,
you'll have plenty of air flow.
I suspect the 'big guys' in aviation lighting
already do this. After all, there are TSO
requirements for thermal robustness that
have to be met and by now, they're very
good at it. If you're looking at a DIY
LED illumination project, start with a study
of how the big guys do it.
When assigned a task for development of
a new product in years past, one of the
first things I would do it search out
the patents on legacy technology. HISTORY
can give you a leg up on avoiding
exercises in re-invention.
>Am I right in assuming the plate has to be
>thickest were the LED is mounted and then taper
>down in thickness as it expands out in width and height?
No . . . thermal resistance of base material,
surface area and AIRFLOW . . . but without
a doubt, include ELECTRONIC overheat
protection.
Bob . . .
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
Thanks Todd. There are a multitude of LED solutions out there. I have a
$20 4oz Trustfire 3T6 flashlight head that puts out 1,300 lumens
(actually capable of 3,300 if I can get to and modify the internal
driver in it and add proper cooling).
However , the 10 watt Cree XM-L2 or similar LED chips can now be had for
$1.64 each. That's about 1,160 lumens if fed 10 watts. The newer XHP35,
XHP72, etc. may or may not be slightly more efficient, but puts out
light from a more dense location but are more expensive.
The point here is that the LED solutions all come with (heavy) heat
sinks. Even the drivers will need some cooling (think mounting the
driver ICs/diodes on a wing rib).
70 to 80% of the power being fed to the LED chips needs to be dissipated
as heat. That's right, LEDs are not more than 20 to 30% efficient!
All commercial and DIY LED landing light solutions I've seen so far come
stand-alone. But why not design it into the aircraft? I guess not
everyone is a weight freak like me.
Reason for using flashlight (torch) heads is they come with reflectors
-- trick is to find ones with a narrow beam and low loss reflector and
not having to pay for battery holder tube, heat sink, batteries etc.
etc. But they all come with integrated drivers and heat sinks.
Some torches come with adjustable beam, but from what I've read they
have rather lossy reflectors.
Now, a reflector like this https://www.stratusleds.com/module should
probably do it, although I don't know the beam width. That's what
started me thinking about using the LE wing skin as the heat sink. Needs
a mount plate that can transfer the 70 or 80 watts of heat from the
34x34mm LED chip base to a sufficient area of wing skin. What's the heat
"resistance" of 0.025 thick alum?
Finn
On 11/1/2020 2:58 AM, Todd Bartrim wrote:
> Ooops, that was the link for my own collection of reference photos,
> This is the one you need to see how I did the lights
> https://photos.app.goo.gl/wQvyosNK1QBFjz7c8
> Todd Bartrim
>
>
> On Sun, Nov 1, 2020 at 12:54 AM Todd Bartrim <bartrim@gmail.com
> <mailto:bartrim@gmail.com>> wrote:
>
> Hi Finn;
> This may not be using the skin as a heat sink, but it works
> great and is lightweight.
> I bought some of these lights from Amazon and took them apart to
> make my landing lights.
> https://www.amazon.ca/Lightfox-Driving-Offroad-Waterproof-Warranty/dp/B01M98GWR2/ref=sr_1_2_sspa?crid=31MNRKKNOSJAA&dchild=1&keywords=led+spot+lights+offroad&qid=1604214923&sprefix=led+spot+%2Caps%2C274&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEySTdLUVhZSDFQQTEmZW5jcnlwdGVkSWQ9QTA2NDM1NzcyUVdZV1QyR0tJS1dRJmVuY3J5cHRlZEFkSWQ9QTAwNzU1NTUzSzVRRTYzNTZSUjZHJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ=
> this is from Amazon's Canada site, but I'm sure you can find them
> even cheaper on the US site.
> Then I took them apart as you can see in thesepictures posted
> here on Google photos
> https://photos.app.goo.gl/S68h3zpVy7RVJDTT8
> I can't rememberhow much weight I discarded from the parts I
> removed, but it was most of the weight of the light.
> The mounting plate was originally part of the Duckworths landing
> light that I wasted my money on. That is a simple part to make. I
> have 2 of those mounted mid wing and are pointed down for use as
> taxi lights, then I mounted 2 into the wingtips (required some
> fibreglass work) and have them pointed straight ahead for landing
> lights.
> These lights are very durable and bright. I must have bought more
> than a dozen so far as I've put some on my truck, my son's Jeep,
> my skidsteer, 4 on the plane and probably the harshest duty is the
> pair I put on my ATV, which are thoroughly abused. They are
> extremely bright in the bush with very little current draw so my
> ATV has no problem running them continuously. I think those ones
> are at least 4 years old and are still working great despite the
> abuse.
> It looks like there are even better versions of these lights
> now, that appear to be the same construction so you can still
> dismantle them to get the good parts only.
>
> Todd Bartrim
> RV9
> 13Bturbo
>
> On Sat, Oct 31, 2020 at 8:20 PM Finn Lassen <finn.usa@gmail.com
> <mailto:finn.usa@gmail.com>> wrote:
>
> <finn.usa@gmail.com <mailto:finn.usa@gmail.com>>
>
> Might say the most critical thing for LED life and high lumens
> output is
> conducting heat away from the LED.
>
> That usually means attaching heavy heat sinks.
>
> Could we save weight by using the wing skin as a heat sink?
>
> I understand it would present problems in adjusting (pointing)
> the light.
>
> But, could we bond/attach the LED to a (alum?) plate that is then
> bonded/riveted/screwed to the leading edge wing skin?
>
> Let's say we use a 100W LED (~13,000 lumens). We'd have to
> remove 70 to
> 80W of heat from the LED. LED doesn't like more than 150C and
> it would
> be better to keep it cooler. LED area 34x34mm.
>
> I don't have a good grasp of thermal conductivity
> (conductance?). How
> thick would the mount plate have to be? How much area would be
> needed
> where the mount plate contacts the wing skin (using some kind
> of heat
> sink compound/adhesive between the plate and skin)?
>
> Am I right in assuming the plate has to be thickest were the
> LED is
> mounted and then taper down in thickness as it expands out in
> width and
> height?
>
> Perhaps tapered layers of carbon fiber (with thermal epoxy)
> would be
> better as the LED mount plate? (After a diamond, graphene or
> graphite
> apparently has the best thermal conductivity.)
>
> Any (thermal) engineers here that could enlighten me?
>
> Finn
>
>
> ---
> This email has been checked for viruses by Avast antivirus
> software.
> https://www.avast.com/antivirus
>
> ==========
> -
> Electric-List" rel="noreferrer"
> target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
> ==========
> FORUMS -
> eferrer" target="_blank">http://forums.matronics.com
> ==========
> WIKI -
> errer" target="_blank">http://wiki.matronics.com
> ==========
> b Site -
> -Matt Dralle, List Admin.
> rel="noreferrer"
> target="_blank">http://www.matronics.com/contribution
> ==========
>
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
>Let's say we use a 100W LED (~13,000 lumens). We'd have to remove 70
>to 80W of heat from the LED.
AND the associated electronics.
See attached:
Bob . . .
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
At 07:46 AM 11/1/2020, you wrote:
>
>That would introduce drag.
>
>Name of the game here is no drag and lowest possible weight for max
>light output (lumens) directed in a narrow beam that can reach 3,000
>feet or more down a deer infested runway.
Save yourself a LOT of fuss and bother.
Consider adapting a COTs LED assembly
to your task. There's a boat-load of
really capable emitters with built
in power supplies and cooling. I got
'em on all my vehicles.
Dirt is more expensive . . .
https://tinyurl.com/y5kky5f6
Bob . . .
Message 10
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
Sorry, I was looking at the Cree XM-L2. 116 l/w. 116/350 = 33%. At
least 5% loss in the driver. So about 31% or 69% heat dissipation. (Not
sure about optical efficiency. I guess that's heat in the lens and
reflector.)
So thickness of mount plate should not be a factor? A 10W LED I have has
a 1.6mm thick metal base, but I guess that's needed to screw it down to
heat sink with proper contact (minimal heat sink compound thickness).
Alum: 205 W/mK or 0.205W/C. But, but ... is cross area not a factor?
Trying to compare it to electrical resistance in a wire. The higher the
cross area -- the less resistance.
Trying to wrap my head around the transition from flat contact area
under the LED chip to the heat sink plate as it expands out in area.
Seems mounting it to an infinite piece of alum foil would not be the
same as mounting it to 10x10" 0.063" thick alum plate ...
Finn
On 11/1/2020 9:25 AM, Robert L. Nuckolls, III wrote:
>> Let's say we use a 100W LED (~13,000 lumens). We'd have to remove 70
>> to 80W of heat from the LED.
>
> AND the associated electronics.
>
> See attached:
>
>
> Bob . . .
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 11
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
I got might lights from https://www.mpja.com/20-30-50-Watt-LEDs/products/5
80/
The drivers are riveted to the wing skin and the LED riveted to a plate of
.080" aluminum.=C2- They were then riveted to Zenith's mount plate (I hav
e a 601XL).=C2- I didn't bother to use any reflectors, as the LEDs tend t
o concentrate light in one area.=C2- One 30W driver wiill handle three 10
W LEDs.=C2- That will spread the heat out.=C2-
Cooling air is provided by a 1/8" hole drilled to stop a crack in the plexi
glass cover=C2- :-)=C2- If anyone can measure the drag of that 1/8" hol
e, you're smart enough that I want to be your friend.
On Sunday, November 1, 2020, 10:02:03 AM EST, Finn Lassen <finn.usa@gma
il.com> wrote:
Sorry, I was looking at the Cree XM-L2.=C2- 116 l/w. 116/350 = 33%. At
least 5% loss in the driver. So about 31% or 69% heat dissipation. (Not sur
e about optical efficiency. I guess that's heat in the lens and reflector.)
So thickness of mount plate should not be a factor? A 10W LED I have has a
1.6mm thick metal base, but I guess that's needed to screw it down to heat
sink with proper contact (minimal heat sink compound thickness).
Alum: 205 W/mK or 0.205W/C. But, but ... is cross area not a factor? Trying
to compare it to electrical resistance in a wire.=C2- The higher the cro
ss area -- the less resistance.
Trying to wrap my head around the transition from flat contact area under t
he LED chip to the heat sink plate as it expands out in area. Seems mountin
g it to an infinite piece of alum foil would not be the same as mounting it
to 10x10" 0.063" thick alum plate ...
Finn
On 11/1/2020 9:25 AM, Robert L. Nuckolls, III wrote:
Let's say we use a 100W LED (~13,000 lumens). We'd have to remove 70 to 80W
of heat from the LED.
=C2- AND the associated electronics.
=C2-
=C2- See attached:
=C2- Bob . . .
| | Virus-free. www.avast.com |
Message 12
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat |
sink?
>
>
>Trying to wrap my head around the transition from flat contact area
>under the LED chip to the heat sink plate as it expands out in area.
>Seems mounting it to an infinite piece of alum foil would not be the
>same as mounting it to 10x10" 0.063" thick alum plate ...
But the sheet has thermal resistance too. And
rate of dissipation is a function of temperature
differential. As you move out onto the sheet,
the fastest transfer is right around the base
of the LED; temperatures fall as you move
out hence energy dissipated per unit area
declines.
Intuitively, it makes sense that 'sink'
temperature at the base of the LED will
be much higher than at a remote location.
Are we talking about landing lights?
Bob . . .
Message 13
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat |
sink?
At 11:03 AM 11/1/2020, you wrote:
>>Trying to wrap my head around the transition from flat contact area
>>under the LED chip to the heat sink plate as it expands out in
>>area. Seems mounting it to an infinite piece of alum foil would not
>>be the same as mounting it to 10x10" 0.063" thick alum plate ...
>
> But the sheet has thermal resistance too. And
> rate of dissipation is a function of temperature
> differential. As you move out onto the sheet,
> the fastest transfer is right around the base
> of the LED; temperatures fall as you move
> out hence energy dissipated per unit area
> declines.
>
> Intuitively, it makes sense that 'sink'
> temperature at the base of the LED will
> be much higher than at a remote location.
>
> Are we talking about landing lights?
Duuh . . . need another cup of coffee . . .
Is this the kind of critter we're talking
about?
https://tinyurl.com/y4tespt7
Do you have a link to share for the
exact device and its spec sheet?
Bob . . .
Message 14
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
On 11/1/2020 12:03 PM, Robert L. Nuckolls, III wrote:
>>
>>
>> Trying to wrap my head around the transition from flat contact area
>> under the LED chip to the heat sink plate as it expands out in area.
>> Seems mounting it to an infinite piece of alum foil would not be the
>> same as mounting it to 10x10" 0.063" thick alum plate ...
>
> But the sheet has thermal resistance too. And
> rate of dissipation is a function of temperature
> differential. As you move out onto the sheet,
> the fastest transfer is right around the base
> of the LED; temperatures fall as you move
> out hence energy dissipated per unit area
> declines.
>
> Intuitively, it makes sense that 'sink'
> temperature at the base of the LED will
> be much higher than at a remote location.
>
> Are we talking about landing lights?
>
>
> Bob . . .
>
Yes landing lights.
So my understanding is right. Thicker plate near LED base, then tapering
out. You'll also see that in old big heat sinks: thick base then fins
tapering out. I guess optimal design is total surface area versus
enough material to conduct the heat to the entire surface (when
designing for least weight). Some newer heat sinks I've seen have
numerous rods sticking out from the base. Perhaps (for least weight) the
rods should actually be tapered.
This my original question: "Am I right in assuming the plate has to be
thickest were the LED is mounted and then taper down in thickness as it
expands out in width and height?"
Another interesting item from Googling "best thermal conductivity":
"Along with its carbon cousins graphite and graphene, diamond is the
best thermal conductor around room temperature, having thermal
conductivity of more than 2,000 watts per meter per Kelvin, which is
five times higher than the best metals such as *copper*."
leading to my: "Perhaps tapered layers of carbon fiber (with thermal
epoxy) would be better as the LED mount plate? (After a diamond,
graphene or graphite apparently has the best thermal conductivity.)"
One could shape the carbon fiber layup to closely fit the leading edge skin.
I guess I'm thinking way, way, way too far out of the box :)
Finn
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 15
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
Yes, that's where I got the position and strobe LEDs I'm working with at
the moment, thanks to your posting here a long time ago.
Got 5 of the 10W super white LEDs. One for tail position/strobe. Two for
each wingtip strobe.I also got the 10W green and red ones for wing
position lights.
The tail LED will be driven with 300mA (via series diode) as a position
light and then high-current pulses for strobing it.
I've read of over-driving LEDs for strobes. Max specs for the 10W LEDs
says 1 amp, 1.5A peak. I would like to give them a 100ms (or less) 10A
pulse. My big question is if that would violate the 1.5A peak spec.
Fiddling with a LM324 quad single-supply op-amp. Looking at application
examples I found that it's actually possible to make just one op-amp
generate 100ms pulses every 1 sec with 5 resistors, one capacitor and
one diode. Also can run directly on ship's power. (max 32V). Now I'm
looking for a P-channel MOSFET to drive the LED to max voltage. I guess
I could use a PNP power transistor I've got laying around ...
Finn
On 11/1/2020 11:06 AM, Ernest Christley wrote:
> I got might lights from
> https://www.mpja.com/20-30-50-Watt-LEDs/products/580/
>
> The drivers are riveted to the wing skin and the LED riveted to a
> plate of .080" aluminum. They were then riveted to Zenith's mount
> plate (I have a 601XL). I didn't bother to use any reflectors, as the
> LEDs tend to concentrate light in one area. One 30W driver wiill
> handle three 10W LEDs. That will spread the heat out.
>
> Cooling air is provided by a 1/8" hole drilled to stop a crack in the
> plexiglass cover :-) If anyone can measure the drag of that 1/8"
> hole, you're smart enough that I want to be your friend.
>
> On Sunday, November 1, 2020, 10:02:03 AM EST, Finn Lassen
> <finn.usa@gmail.com> wrote:
>
>
> Sorry, I was looking at the Cree XM-L2. 116 l/w. 116/350 = 33%. At
> least 5% loss in the driver. So about 31% or 69% heat dissipation.
> (Not sure about optical efficiency. I guess that's heat in the lens
> and reflector.)
>
> So thickness of mount plate should not be a factor? A 10W LED I have
> has a 1.6mm thick metal base, but I guess that's needed to screw it
> down to heat sink with proper contact (minimal heat sink compound
> thickness).
>
> Alum: 205 W/mK or 0.205W/C. But, but ... is cross area not a factor?
> Trying to compare it to electrical resistance in a wire. The higher
> the cross area -- the less resistance.
>
> Trying to wrap my head around the transition from flat contact area
> under the LED chip to the heat sink plate as it expands out in area.
> Seems mounting it to an infinite piece of alum foil would not be the
> same as mounting it to 10x10" 0.063" thick alum plate ...
>
> Finn
>
>
> On 11/1/2020 9:25 AM, Robert L. Nuckolls, III wrote:
>>> Let's say we use a 100W LED (~13,000 lumens). We'd have to remove 70
>>> to 80W of heat from the LED.
>>
>> AND the associated electronics.
>>
>> See attached:
>>
>>
>>
>> Bob . . .
>>
>
>
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon>
> Virus-free. www.avast.com
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link>
>
>
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 16
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
On Sun, Nov 1, 2020 at 12:59 PM Finn Lassen <finn.usa@gmail.com> wrote:
>
>
> On 11/1/2020 12:03 PM, Robert L. Nuckolls, III wrote:
>
>
> Trying to wrap my head around the transition from flat contact area under
> the LED chip to the heat sink plate as it expands out in area. Seems
> mounting it to an infinite piece of alum foil would not be the same as
> mounting it to 10x10" 0.063" thick alum plate ...
>
>
> But the sheet has thermal resistance too. And
> rate of dissipation is a function of temperature
> differential. As you move out onto the sheet,
> the fastest transfer is right around the base
> of the LED; temperatures fall as you move
> out hence energy dissipated per unit area
> declines.
>
> Intuitively, it makes sense that 'sink'
> temperature at the base of the LED will
> be much higher than at a remote location.
>
> Are we talking about landing lights?
>
>
> Bob . . .
>
> Yes landing lights.
>
> So my understanding is right. Thicker plate near LED base, then tapering
> out. You'll also see that in old big heat sinks: thick base then fins
> tapering out. I guess optimal design is total surface area versus enough
> material to conduct the heat to the entire surface (when designing for
> least weight). Some newer heat sinks I've seen have numerous rods sticking
> out from the base. Perhaps (for least weight) the rods should actually be
> tapered.
>
> This my original question: "Am I right in assuming the plate has to be
> thickest were the LED is mounted and then taper down in thickness as it
> expands out in width and height?"
>
> Another interesting item from Googling "best thermal conductivity":
> "Along with its carbon cousins graphite and graphene, diamond is the best
> thermal conductor around room temperature, having thermal conductivity of
> more than 2,000 watts per meter per Kelvin, which is five times higher than
> the best metals such as *copper*."
>
> leading to my: "Perhaps tapered layers of carbon fiber (with thermal
> epoxy) would be better as the LED mount plate? (After a diamond, graphene
> or graphite apparently has the best thermal conductivity.)"
>
> One could shape the carbon fiber layup to closely fit the leading edge
> skin.
>
> I guess I'm thinking way, way, way too far out of the box :)
>
> Finn
>
Jim Weir has a couple of articles in Kitplanes magazine that give a
'cookbook' method of figuring heatsink size. I don't know, but strongly
suspect that the epoxy used as a binder in a typical carbon layup will more
than kill any thermal advantage of the carbon. How about some aluminum
flashing sheet? Bend up multiple ' [ ' channels with increasing center
widths, stack up up 'concentric' drill for the LED base, then reassemble
with heat sink compound. Not perfect, but a lot faster/cheaper than carbon,
and you get the extra thickness next to the LED.
Of course, by the time you do all that, you'll have spent more in
parts/labor than the FlyLEDs light we talked about, off-line. :-) I doubt
it will be much lighter, either.
Charlie
Message 17
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
Another option is to mount the LED in the center of a disk.=C2- Drill a
ring of 1/8" holes right up next to the LED.=C2- Then a ring of 3/16" hol
es a little further out.=C2- Then a ring of 1/4", etc.The plate provides
a way to mount to the wing.
On Sunday, November 1, 2020, 3:38:03 PM EST, Charlie England <ceengland
7@gmail.com> wrote:
On Sun, Nov 1, 2020 at 12:59 PM Finn Lassen <finn.usa@gmail.com> wrote:
On 11/1/2020 12:03 PM, Robert L. Nuckolls, III wrote:
Trying to wrap my head around the transition from flat contact area under
the LED chip to the heat sink plate as it expands out in area. Seems mounti
ng it to an infinite piece of alum foil would not be the same as mounting i
t to 10x10" 0.063" thick alum plate ...
=C2- But the sheet has thermal resistance too. And
=C2- rate of dissipation is a function of temperature
=C2- differential. As you move out onto the sheet,
=C2- the fastest transfer is right around the base
=C2- of the LED; temperatures fall as you move
=C2- out hence energy dissipated per unit area
=C2- declines.
=C2- Intuitively, it makes sense that 'sink'
=C2- temperature at the base of the LED will
=C2- be much higher than at a remote location.
=C2- Are we talking about landing lights?
=C2- Bob . . .
Yes landing lights.
So my understanding is right. Thicker plate near LED base, then tapering o
ut. You'll also see that in old big heat sinks: thick base then fins taperi
ng out.=C2- I guess optimal design is=C2- total surface area versus eno
ugh material to conduct the heat to the entire surface (when designing for
least weight). Some newer heat sinks I've seen have numerous rods sticking
out from the base. Perhaps (for least weight) the rods should actually be t
apered.
This my original question: "Am I right in assuming the plate has to be thi
ckest were the LED is mounted and then taper down in thickness as it expand
s out in width and height?"
Another interesting item from Googling "best thermal conductivity":
"Along with its carbon cousins graphite and graphene, diamond is the best
thermal conductor around room temperature, having thermal conductivity of m
ore than 2,000 watts per meter per Kelvin, which is five times higher than
the best metals such as copper."
leading to my: "Perhaps tapered layers of carbon fiber (with thermal epoxy
) would be better as the LED mount plate? (After a diamond, graphene or gra
phite apparently has the best thermal conductivity.)"
One could shape the carbon fiber layup to closely fit the leading edge ski
n.
I guess I'm thinking way, way, way too far out of the box :)
Finn
Jim Weir has a couple of articles in Kitplanes magazine that give a 'cookbo
ok' method of figuring heatsink size.=C2- I don't know, but strongly susp
ect that the epoxy used as a binder in a typical carbon layup will more tha
n kill any thermal advantage of the carbon. How about some aluminum flashin
g sheet? Bend up multiple ' [ ' channels with increasing center widths, sta
ck up up 'concentric' drill for the LED base, then reassemble with heat sin
k compound. Not perfect, but a lot faster/cheaper than carbon, and you get
the extra thickness next to the LED.=C2-
Of course, by the time you do all that, you'll have spent more in parts/lab
or than the FlyLEDs light we talked about, off-line. :-) I doubt it will be
much lighter, either.
Charlie
Message 18
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Microair 760 transceivers for sale |
A subscriber to this List has determined
that a couple of Microair 760 transceivers
are surplus to his needs. He asked my assistance
with getting them into new homes.
I've listed them on eBay at auction. All proceeds
will go to Matt Dralle to support his closet
full of byte-thrashers that make all this
good stuff run!
The first is a 7 day listing up now at
https://tinyurl.com/y2lobwew
The second listing is a 10 day auction
that goes 'live' at 1900 PST. Will
post the link later.
Bob . . .
Message 19
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Breaker then pump failure |
>Bob, if I get the old pump back, I'll send it to you along with the
breaker.
Thanks
>BTW, I just became aware of an AD from=C2 2008 to
>replace this type of CB switch in Beechcraft products.
Bingo . . . I worked the failure analysis team
on that fiasco.
As I recall, the risk of failure came to light
when a pilot reported, "smoke squirting from
around the handle on the prop de-ice switch
breaker."
Here's link to relevant pictures and
documents:
https://tinyurl.com/y48y93rk
That was a real can of worms.
There were tens of thousands of switch breakers
in the field covering decades of production in
Bonanzas and Barons. Being a commercial off the
shelf product, it was unclear which fielded
aircraft might be vulnerable to this condition.
I.e. smoke AFTER failure of the braid.
As it turns out, only the prop de-ice switch
breaker had a risk for generating some smoke.
Switches carrying lower currents would
continue to function although loss of the
braided jumper on alternator control switches
increased field supply path resistance
which MIGHT lead to regulator instability.
It was finally deduced that this failure
did not represent any greater hazard than
failure of the protected device . . . hence
removal/replacement of a breaker could
be left 'on condition' as opposed to a fleet
wide swap out.
Of course, ongoing production and spares
breakers have the magic insulator so
the risk of smoke has been mitigated
for the future.
Bob . . .
Message 20
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
>> Are we talking about landing lights?
>>
>>
>> Bob . . .
>Yes landing lights.
Okay . . . in the right pew now.
Is there an engineering data spec sheet available
for the device(s) you're considering?
Do you know the thermal resistance from mounting
surface to LED junction?
Bob . . .
Message 21
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
Cool. But how thick should the disk be?
I don't know why I'm so thermodynamics challenged ...
A Google search finds that alum has a thermal resistance of 0.5W/C. But
what does that mean? There's got to be a formula that includes material
thickness and area.
Electrical resistance in a wire includes cross section (area) of wire
and length. Surely something similar must be the case for thermal
resistance or conductivity.
Charlie, can you point me to the Kitplanes article?
Finn
On 11/1/2020 4:18 PM, Ernest Christley wrote:
> Another option is to mount the LED in the center of a disk. Drill a
> ring of 1/8" holes right up next to the LED. Then a ring of 3/16"
> holes a little further out. Then a ring of 1/4", etc.The plate
> provides a way to mount to the wing.
>
> On Sunday, November 1, 2020, 3:38:03 PM EST, Charlie England
> <ceengland7@gmail.com> wrote:
>
>
> On Sun, Nov 1, 2020 at 12:59 PM Finn Lassen <finn.usa@gmail.com
> <mailto:finn.usa@gmail.com>> wrote:
>
>
> On 11/1/2020 12:03 PM, Robert L. Nuckolls, III wrote:
>>>
>>>
>>> Trying to wrap my head around the transition from flat contact
>>> area under the LED chip to the heat sink plate as it expands out
>>> in area. Seems mounting it to an infinite piece of alum foil
>>> would not be the same as mounting it to 10x10" 0.063" thick alum
>>> plate ...
>>
>> But the sheet has thermal resistance too. And
>> rate of dissipation is a function of temperature
>> differential. As you move out onto the sheet,
>> the fastest transfer is right around the base
>> of the LED; temperatures fall as you move
>> out hence energy dissipated per unit area
>> declines.
>>
>> Intuitively, it makes sense that 'sink'
>> temperature at the base of the LED will
>> be much higher than at a remote location.
>>
>> Are we talking about landing lights?
>>
>>
>> Bob . . .
>>
> Yes landing lights.
>
> So my understanding is right. Thicker plate near LED base, then
> tapering out. You'll also see that in old big heat sinks: thick
> base then fins tapering out. I guess optimal design is total
> surface area versus enough material to conduct the heat to the
> entire surface (when designing for least weight). Some newer heat
> sinks I've seen have numerous rods sticking out from the base.
> Perhaps (for least weight) the rods should actually be tapered.
>
> This my original question: "Am I right in assuming the plate has
> to be thickest were the LED is mounted and then taper down in
> thickness as it expands out in width and height?"
>
> Another interesting item from Googling "best thermal conductivity":
> "Along with its carbon cousins graphite and graphene, diamond is
> the best thermal conductor around room temperature, having thermal
> conductivity of more than 2,000 watts per meter per Kelvin, which
> is five times higher than the best metals such as *copper*."
>
> leading to my: "Perhaps tapered layers of carbon fiber (with
> thermal epoxy) would be better as the LED mount plate? (After a
> diamond, graphene or graphite apparently has the best thermal
> conductivity.)"
>
> One could shape the carbon fiber layup to closely fit the leading
> edge skin.
>
> I guess I'm thinking way, way, way too far out of the box :)
>
> Finn
>
> Jim Weir has a couple of articles in Kitplanes magazine that give a
> 'cookbook' method of figuring heatsink size. I don't know, but
> strongly suspect that the epoxy used as a binder in a typical carbon
> layup will more than kill any thermal advantage of the carbon. How
> about some aluminum flashing sheet? Bend up multiple ' [ ' channels
> with increasing center widths, stack up up 'concentric' drill for the
> LED base, then reassemble with heat sink compound. Not perfect, but a
> lot faster/cheaper than carbon, and you get the extra thickness next
> to the LED.
>
> Of course, by the time you do all that, you'll have spent more in
> parts/labor than the FlyLEDs light we talked about, off-line. :-) I
> doubt it will be much lighter, either.
>
> Charlie
>
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 22
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
On 11/1/2020 6:37 PM, Robert L. Nuckolls, III wrote:
>>> Are we talking about landing lights?
>>>
>>>
>>> Bob . . .
>
>
>> Yes landing lights.
>
> Okay . . . in the right pew now.
>
> Is there an engineering data spec sheet available
> for the device(s) you're considering?
>
> Do you know the thermal resistance from mounting
> surface to LED junction?
>
> Bob . . .
>
Looking at the Cree XM-L2 with a thermal resistance of 2.5W/C from
junction to mount surface. Add to that a conservative 0.5W/C for heat
sink compound and we get 3W/C.
Max die temp is 150C. But unlimited life is 35C. It appears that when
you go above 35C you start reducing life of the LED.
The LEDs are "binned" (color and efficiency determined) at 85C.
So lets set die temp of 85C as the design goal.
With built-in temp limiting, I think we can probably consider wing skin
to air thermal resistance as 0W/C (air flowing over the skin in flight).
Consider 32C ambient we get 85 -3 -32 = 50 allowed temp difference from
mount plate to skin.
Each LED has a mount surface of about 20x20mm.
If we have eight 10W LEDs at 30% efficiency, we need to get rid of 56 watts.
So max thermal resistance of mount plate and mount late to wing skin
should be 56/50 = 1.1W/C. If we use heat sink compound between plate and
wing skin, we're down to 0.6W/C max thermal resistance of the mount
plate. Wow! Can that be right?
If alum has thermal resistance of 0.2 W/C we need 3 of something. What
is the something? Thickness vs area? This is where I bog down.
Finn
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 23
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: ADS-B and Transponder antenna... |
Here's another useful resource for learning the nanoVNA. It's a demo board that
you connect to the device in order to learn what the test response should look
like for various kinds of circuits.
https://preview.tinyurl.com/yxz2hast
I bought one and it seems to be well made. My only complaint is the tiny U.FL
connectors they used on the board. They're a bit of a pain to mate, and they're
only designed for a few dozen mating cycles, so it's not a lifetime tool.
But hey, whaddya want for $13.00?!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=499175#499175
Message 24
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
On 11/1/2020 5:53 PM, Finn Lassen wrote:
>
> Cool. But how thick should the disk be?
>
> I don't know why I'm so thermodynamics challenged ...
>
> A Google search finds that alum has a thermal resistance of 0.5W/C.
> But what does that mean? There's got to be a formula that includes
> material thickness and area.
>
> Electrical resistance in a wire includes cross section (area) of wire
> and length. Surely something similar must be the case for thermal
> resistance or conductivity.
>
> Charlie, can you point me to the Kitplanes article?
>
> Finn
>
>
> On 11/1/2020 4:18 PM, Ernest Christley wrote:
>> Another option is to mount the LED in the center of a disk. Drill a
>> ring of 1/8" holes right up next to the LED. Then a ring of 3/16"
>> holes a little further out. Then a ring of 1/4", etc.The plate
>> provides a way to mount to the wing.
>>
>> On Sunday, November 1, 2020, 3:38:03 PM EST, Charlie England
>> <ceengland7@gmail.com> wrote:
>>
>>
>>
>>
>> On Sun, Nov 1, 2020 at 12:59 PM Finn Lassen <finn.usa@gmail.com
>> <mailto:finn.usa@gmail.com>> wrote:
>>
>>
>>
>> On 11/1/2020 12:03 PM, Robert L. Nuckolls, III wrote:
>>>>
>>>>
>>>> Trying to wrap my head around the transition from flat contact
>>>> area under the LED chip to the heat sink plate as it expands
>>>> out in area. Seems mounting it to an infinite piece of alum
>>>> foil would not be the same as mounting it to 10x10" 0.063"
>>>> thick alum plate ...
>>>
>>> But the sheet has thermal resistance too. And
>>> rate of dissipation is a function of temperature
>>> differential. As you move out onto the sheet,
>>> the fastest transfer is right around the base
>>> of the LED; temperatures fall as you move
>>> out hence energy dissipated per unit area
>>> declines.
>>>
>>> Intuitively, it makes sense that 'sink'
>>> temperature at the base of the LED will
>>> be much higher than at a remote location.
>>>
>>> Are we talking about landing lights?
>>>
>>>
>>> Bob . . .
>>>
>> Yes landing lights.
>>
>> So my understanding is right. Thicker plate near LED base, then
>> tapering out. You'll also see that in old big heat sinks: thick
>> base then fins tapering out. I guess optimal design is total
>> surface area versus enough material to conduct the heat to the
>> entire surface (when designing for least weight). Some newer heat
>> sinks I've seen have numerous rods sticking out from the base.
>> Perhaps (for least weight) the rods should actually be tapered.
>>
>> This my original question: "Am I right in assuming the plate has
>> to be thickest were the LED is mounted and then taper down in
>> thickness as it expands out in width and height?"
>>
>> Another interesting item from Googling "best thermal conductivity":
>> "Along with its carbon cousins graphite and graphene, diamond is
>> the best thermal conductor around room temperature, having
>> thermal conductivity of more than 2,000 watts per meter per
>> Kelvin, which is five times higher than the best metals such as
>> *copper*."
>>
>> leading to my: "Perhaps tapered layers of carbon fiber (with
>> thermal epoxy) would be better as the LED mount plate? (After a
>> diamond, graphene or graphite apparently has the best thermal
>> conductivity.)"
>>
>> One could shape the carbon fiber layup to closely fit the leading
>> edge skin.
>>
>> I guess I'm thinking way, way, way too far out of the box :)
>>
>> Finn
>>
>> Jim Weir has a couple of articles in Kitplanes magazine that give a
>> 'cookbook' method of figuring heatsink size. I don't know, but
>> strongly suspect that the epoxy used as a binder in a typical carbon
>> layup will more than kill any thermal advantage of the carbon. How
>> about some aluminum flashing sheet? Bend up multiple ' [ ' channels
>> with increasing center widths, stack up up 'concentric' drill for the
>> LED base, then reassemble with heat sink compound. Not perfect, but a
>> lot faster/cheaper than carbon, and you get the extra thickness next
>> to the LED.
>>
>> Of course, by the time you do all that, you'll have spent more in
>> parts/labor than the FlyLEDs light we talked about, off-line. :-) I
>> doubt it will be much lighter, either.
>>
>> Charlie
>>
>
Boy, am I glad that this thread isn't a novel.
Finn,
Try this link (you probably need a subscription to access it):
https://www.kitplanes.com/aero-lectrics-141/
There are a lot of other articles by Weir that deal with it, too. I just
logged in and searched for 'heat sink', and watched for Weir's name as
author.
Charlie
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 25
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: DIY LED landing light -- Wing skin as heat sink? |
https://electronics.stackexchange.com/questions/294583/does-heatsink-trans
fer-plate-thickness-matter
I think the 4th answer down give the answer.=C2- Draw out the path of whe
re you are inputting the heat (back of the module), to where air starts flo
wing over it.
If it were me, I'd mount it on an 0.80 or 0.90 plate and tape a thermocoupl
e on the back.=C2- Maybe set a fan in front to simulate the prop turning.
=C2- If not cool enough, use a thicker plate, or drill more holes.
On Sunday, November 1, 2020, 7:42:33 PM EST, Finn Lassen <finn.usa@gmai
l.com> wrote:
On 11/1/2020 6:37 PM, Robert L. Nuckolls, III wrote:
=C2- Are we talking about landing lights?
=C2- Bob . . .
Yes landing lights.
=C2- Okay . . . in the right pew now.
=C2- Is there an engineering data spec sheet available
=C2- for the device(s) you're considering?
=C2- Do you know the thermal resistance from mounting
=C2- surface to LED junction?
=C2- Bob . . .
Looking at the Cree XM-L2 with a thermal resistance of 2.5W/C from junctio
n to mount surface. Add to that a conservative 0.5W/C for heat sink compoun
d and we get 3W/C.
Max die temp is 150C. But unlimited life is 35C. It appears that when you
go above 35C you start reducing life of the LED.
The LEDs are "binned" (color and efficiency determined)=C2- at 85C.
So lets set die temp of 85C as the design goal.
With built-in temp limiting, I think we can probably consider wing skin to
air thermal resistance as 0W/C (air flowing over the skin in flight).
Consider 32C ambient we get 85 -3 -32 = 50 allowed temp difference from
mount plate to skin.
Each LED has a mount surface of about 20x20mm.
If we have eight 10W LEDs at 30% efficiency, we need to get rid of 56 watt
s.
So max thermal resistance of mount plate and mount late to wing skin shoul
d be 56/50 = 1.1W/C. If we use heat sink compound between plate and wing
skin, we're down to 0.6W/C max thermal resistance of the mount plate. Wow!
Can that be right?
If alum has thermal resistance of 0.2 W/C we need 3 of something. What is
the something? Thickness vs area? This is where I bog down.
Finn
| | Virus-free. www.avast.com |
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|