Today's Message Index:
----------------------
1. 01:40 AM - Electrical system design (Mickey Coggins)
2. 02:47 AM - The LOC... (Matt Dralle)
3. 11:35 AM - Re: PowerSchottky (Robert L. Nuckolls, III)
4. 11:50 AM - Re: which current to monitor in flight? (Robert L. Nuckolls, III)
5. 12:27 PM - Re: PowerSchottky (Stewart, Michael (ISS Atlanta))
6. 07:20 PM - U Shaped Safety Guard (PeterHunt1@aol.com)
7. 07:47 PM - Re: U Shaped Safety Guard (Jim Jewell)
8. 08:31 PM - Re: U Shaped Safety Guard (Scott Jackson)
9. 11:28 PM - Re: U Shaped Safety Guard (Richard Riley)
Message 1
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| Subject: | Electrical system design |
--> AeroElectric-List message posted by: Mickey Coggins <mick-matronics@rv8.ch>
Hi Ken,
>I thought that the standard moveable switchguard could be mounted upside
>down to guard a switch on ?
It probably can, but won't that look kind of funky?
>If an internal voltage regulator is fried then tuning off the +12 volts
>to it may not turn off the alternator even if it did turn off the
>alternator before the regulator failed.
This is what Eric told me in a recent E-mail. The contactor
to cut off the alternator seems to be a must to stop a crazy
alternator.
>All the subaru starters that I've seen do have an integral contactor.
>They don't normally have that jumper from the battery terminal to the
>push on solenoid connection on the car.
I've changed the diagram to reflect this. I don't have the
engine yet, so I seemed to have guessed wrongly on what it would
look like.
>Other switch position philosophies include: - left/right if there is no
>normal position.
> - all down for shutdown
> - anywhere for normal but all up for a problem
I'm probably going to play with this and perhaps change it a few
times until I'm happy with it. I will consider changing my
battery switches to 2-3 double pole on-on switches to see if
I can create a failsafe way to bring the alternator online.
I want to make the system as robust and simple as possible,
keeping in mind Einstein's
"Everything should be made as simple as possible, but not simpler."
>Isn't the short wire to the fuse block considered one of those safe fat
>wires that does not normally get any fuse protection. Similar to no fuse
>protection at the battery for the battery cables.
That's what I understand to be the case. The fuse block for these
will a few inches from the batteries.
--
Mickey Coggins
http://www.rv8.ch/
#82007 QB Wings/Fuselage
Message 2
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--> AeroElectric-List message posted by: Matt Dralle <dralle@matronics.com>
Hi Listers,
The List of Contributors (LOC) is just around the corner! On December 1st
I post a list of everyone that so generously made a Contribution to support
the Lists. Its sort of my way of publicly thanking everyone that took a
minute to show their appreciation for the Lists.
Won't you take a moment and assure that your name is on that List of
Contributors? As a number of people have pointed out, the List seems at
least, if not a whole lot more, as valuable as a building/flying/recreating
tool as a typical your magazine subscription. We won't even talk about a
newsstand price... :-)
Won't you take minute and assure that your name is on the upcoming
LOC? Tell others that you appreciate the Lists. Making a Contribution to
support the Lists is fast and easy using your Visa or M/C on the SSL Secure
Web Site:
http://www.matronics.com/contribution
or by popping a personal check in the mail to:
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c/o Matt Dralle
PO Box 347
Livermore CA 94551-0347
I would like to thank everyone that has so generously made a Contribution
thus far in this year's List Fund Raiser! Remember that its YOUR support
that keeps these Lists going and improving! Don't forget to include a
little comment about how the Lists have helped you! I love to feel the
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Best regards,
Matt Dralle
Email List Administrator
Matt G Dralle | Matronics | PO Box 347 | Livermore | CA | 94551
925-606-1001 V | 925-606-6281 F | dralle@matronics.com Email
http://www.matronics.com/ WWW | Featuring Products For Aircraft
do not archive
Message 3
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| Subject: | Re: PowerSchottky |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 07:22 PM 11/21/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
>
> >> ...Schottky diodes, ....and found 20L15T diodes on Digikey for
>$1.31USD..... The
> >>specs look good to me (20V, 15A, less than .5V forward drop).
>
> >>Any suggestions from the list??
>
>Be careful! When the vendor say a Schottky is good for 15A, he means 15A at
>50% duty cycle. That's 7.5A for you and me. And 20V is really on the ragged
>edge of the requirement. Most assuredly the Schottky 20L15T diode WILL NOT
>DO.
??? I'm looking at the data sheet on the 20L15T at:
http://www.irf.com/product-info/datasheets/data/20l15t.pdf
I find that it's a 20 AMP (not 15A) device, and 15 VOLT (not 20V) device.
Most rectifiers are used in power supplies where they conduct
on every other half-cycle or 50% duty cycle. This means that
peak and average currents through the device are different. Voltage
drop is a function of peak current while thermal considerations are
based on average values.
The "50% duty cycle" notation is simply a recognition of the
way that power supply rectifiers work and is not a suggestion
that the part be de-rated to 1/2 it's average current for use
in applications where DC power is being routed around.
>No mystery. The Schottky I sell is International Rectifier p/n 122NQ030R.
>This is a beefy package with a wide die that makes for very very low Vf of
>under 0.2 V, and will carry 60 Amps in a pinch.
This part will carry a whole lot more than 60A and you don't even
have to pinch it . . . but you DO need to maintain the device's
case at some relatively low temperature. For example, looking at
figure 6 of the data sheet . . .
http://www.irf.com/product-info/datasheets/data/122nq030.pdf
we find a curve for DC applications telling us that the device will
carry 120A DC while dissipating about 48W without exceeding
the RMS dissipation limits also depicted on this graph.
Thermal resistance of this part from junction to case is 0.4
degrees-C/Watt so the junction will rise about 20 degrees
C at 48W dissipation. This means that the case must be
limited to 130 degrees C or less.
With a 50C ambient, the thermal resistance from case to
ambient is (130-50)/48 or 1.7 degrees C/W maximum for the
device to carry 120A.
Note that Figure 5 supports this analysis where it shows
us that the device's case temperature must be held at or
below 130C for a DC forward current of 120A.
Bob . . .
Message 4
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| Subject: | Re: which current to monitor in flight? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 10:34 PM 11/21/2004 +0000, you wrote:
>--> AeroElectric-List message posted by: luckymaCY@comcast.net (lucky)
>
>I have one hall effect current sensor with my EIS. Which is most
>preferred measurement? Measuring battery amps (scale centered at zero) or
>alternator amps.
>
>I think it's battery but wanted a second opinion.
>
>thx,
>lucky
>
>I have one hall effect current sensor with my EIS. Which is most preferred
>measurement? Measuring battery amps (scale centered at zero) or alternator
>amps.
>
>I think it's battery but wanted a second opinion.
>
>thx,
>lucky
Current monitoring preferences are just that . . . preferences.
Whatever current you choose to measure, make sure you know the
significance of what the instrument shows you. If you've
conducted and confirmed a load-analysis, there are no
current measurements useful to pilots for in-flight decision
making. Further, when it comes time to troubleshoot
some system in your airplane, it's likely that you'll want
some current measurement that is NOT displayed on the panel
and needs support from your hand-held multimeter. So pick a
current you like and measure it.
Bob . . .
Bob . . .
--------------------------------------------------------
< Throughout history, poverty is the normal condition >
< of man. Advances which permit this norm to be >
< exceeded -- here and there, now and then -- are the >
< work of an extremely small minority, frequently >
< despised, often condemned, and almost always opposed >
< by all right-thinking people. Whenever this tiny >
< minority is kept from creating, or (as sometimes >
< happens) is driven out of a society, the people >
< then slip back into abject poverty. >
< >
< This is known as "bad luck". >
< -Lazarus Long- >
<------------------------------------------------------>
http://www.aeroelectric.com
Message 5
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--> AeroElectric-List message posted by: "Stewart, Michael (ISS Atlanta)" <mstewart@iss.net>
Ahh the sweet sound of total confusion. I have a 15 year old EE degree
and it might as well have been in literature.
I love you guys and this list. I forget more than I never remember.
Keeps me very humble.
Thanks Bob and team.
Mike Stewart
Pulling wires on the S8. Yipee!
Do not archive
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L. Nuckolls, III
Subject: Re: AeroElectric-List: PowerSchottky
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<b.nuckolls@cox.net>
At 07:22 PM 11/21/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: "Eric M. Jones"
<emjones@charter.net>
>
> >> ...Schottky diodes, ....and found 20L15T diodes on Digikey for
>$1.31USD..... The
> >>specs look good to me (20V, 15A, less than .5V forward drop).
>
> >>Any suggestions from the list??
>
>Be careful! When the vendor say a Schottky is good for 15A, he means
15A at
>50% duty cycle. That's 7.5A for you and me. And 20V is really on the
ragged
>edge of the requirement. Most assuredly the Schottky 20L15T diode WILL
NOT
>DO.
??? I'm looking at the data sheet on the 20L15T at:
http://www.irf.com/product-info/datasheets/data/20l15t.pdf
I find that it's a 20 AMP (not 15A) device, and 15 VOLT (not 20V)
device.
Most rectifiers are used in power supplies where they conduct
on every other half-cycle or 50% duty cycle. This means that
peak and average currents through the device are different. Voltage
drop is a function of peak current while thermal considerations are
based on average values.
The "50% duty cycle" notation is simply a recognition of the
way that power supply rectifiers work and is not a suggestion
that the part be de-rated to 1/2 it's average current for use
in applications where DC power is being routed around.
>No mystery. The Schottky I sell is International Rectifier p/n
122NQ030R.
>This is a beefy package with a wide die that makes for very very low Vf
of
>under 0.2 V, and will carry 60 Amps in a pinch.
This part will carry a whole lot more than 60A and you don't even
have to pinch it . . . but you DO need to maintain the device's
case at some relatively low temperature. For example, looking at
figure 6 of the data sheet . . .
http://www.irf.com/product-info/datasheets/data/122nq030.pdf
we find a curve for DC applications telling us that the device will
carry 120A DC while dissipating about 48W without exceeding
the RMS dissipation limits also depicted on this graph.
Thermal resistance of this part from junction to case is 0.4
degrees-C/Watt so the junction will rise about 20 degrees
C at 48W dissipation. This means that the case must be
limited to 130 degrees C or less.
With a 50C ambient, the thermal resistance from case to
ambient is (130-50)/48 or 1.7 degrees C/W maximum for the
device to carry 120A.
Note that Figure 5 supports this analysis where it shows
us that the device's case temperature must be held at or
below 130C for a DC forward current of 120A.
Bob . . .
Message 6
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| Subject: | U Shaped Safety Guard |
--> AeroElectric-List message posted by: PeterHunt1@aol.com
Ken,
What is this U shaped safety guard you speak of to prevent accidentally
turning a switch off? Is it commercially available?
Pete
RV-6 - almost done
Message 7
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| Subject: | Re: U Shaped Safety Guard |
--> AeroElectric-List message posted by: "Jim Jewell" <jjewell@telus.net>
Hi Ken,
I made one of my own using some .020 annealed stainless steel. I used a
thick paper template to get the shape I wanted then cut nand bent using the
vise etc.I found that using the unibit for sizing the hole after doing the
bending that was best.
Jim in Kelowna
----- Original Message -----
From: <PeterHunt1@aol.com>
Subject: AeroElectric-List: U Shaped Safety Guard
> --> AeroElectric-List message posted by: PeterHunt1@aol.com
>
> Ken,
>
> What is this U shaped safety guard you speak of to prevent accidentally
> turning a switch off? Is it commercially available?
>
> Pete
> RV-6 - almost done
>
>
>
Message 8
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| Subject: | Re: U Shaped Safety Guard |
--> AeroElectric-List message posted by: "Scott Jackson" <jayeandscott@telus.net>
I made mine from thick-walled square aluminum tubing. A few minutes on the
bandsaw and Scotchbrite wheel and it looks very sharp.
----- Original Message -----
From: "Jim Jewell" <jjewell@telus.net>
Subject: Re: AeroElectric-List: U Shaped Safety Guard
> --> AeroElectric-List message posted by: "Jim Jewell" <jjewell@telus.net>
>
> Hi Ken,
>
> I made one of my own using some .020 annealed stainless steel. I used a
> thick paper template to get the shape I wanted then cut nand bent using
> the
> vise etc.I found that using the unibit for sizing the hole after doing the
> bending that was best.
>
> Jim in Kelowna
> ----- Original Message -----
> From: <PeterHunt1@aol.com>
> To: <aeroelectric-list@matronics.com>
> Subject: AeroElectric-List: U Shaped Safety Guard
>
>
>> --> AeroElectric-List message posted by: PeterHunt1@aol.com
>>
>> Ken,
>>
>> What is this U shaped safety guard you speak of to prevent accidentally
>> turning a switch off? Is it commercially available?
>>
>> Pete
>> RV-6 - almost done
>>
>>
>>
>
>
>
Message 9
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| Subject: | Re: U Shaped Safety Guard |
--> AeroElectric-List message posted by: Richard Riley <richard@riley.net>
At 07:17 PM 11/22/04, you wrote:
>--> AeroElectric-List message posted by: PeterHunt1@aol.com
>
>Ken,
>
>What is this U shaped safety guard you speak of to prevent accidentally
>turning a switch off? Is it commercially available?
I got several here, they're beautifully done and cheap
http://www.periheliondesign.com/switchguards.htm
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