Today's Message Index:
----------------------
1. 03:07 AM - Re: AeroElectric-List Digest: 19 Msgs - 10/03/05 (Graham Singleton)
2. 05:51 AM - Noisy Blower (Fiveonepw@aol.com)
3. 08:17 AM - Re:Battery Problem (Frank Stringham)
4. 08:31 AM - Re: Fox tails anyone? (Eric M. Jones)
5. 08:44 AM - Re: Fox tails anyone? (Matt Prather)
6. 10:29 AM - LM-317 & Noise Filtering (J. Mcculley)
7. 10:47 AM - Re: Re: AeroElectric-List Digest: 19 Msgs - (Robert L. Nuckolls, III)
8. 10:52 AM - Re: Re:Battery Problem (Robert L. Nuckolls, III)
9. 11:13 AM - Re: Re: Fox tails anyone? (Robert L. Nuckolls, III)
10. 11:55 AM - Re: LM-317 & Noise Filtering (Eric M. Jones)
11. 01:44 PM - Firewall penetrations (Hinde, Frank George (Corvallis))
12. 02:51 PM - Re: Firewall penetrations (Ken)
13. 03:14 PM - Re: Firewall penetrations (Hinde, Frank George (Corvallis))
14. 05:00 PM - Re: Firewall penetrations (Richard E. Tasker)
15. 07:15 PM - Seeking Dan Checkoway (Bret Smith)
16. 07:44 PM - Re: Re: LM-317 & Noise Filtering (Robert L. Nuckolls, III)
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: | Re: AeroElectric-List Digest: 19 Msgs - 10/03/05 |
--> AeroElectric-List message posted by: Graham Singleton <graham@gflight.f9.co.uk>
<<I'm pretty certain that the XCOM (like it's predecessor in the market -
< Microair 760) will work just fine on typical light aircraft bus fed by
<an automotive alternator. Many ultra-light owners like these tiny
<radios too and they're almost always fitted with PM alternators that
<are NOISY without additional filtering.
<Check the instructions carefully, is the large cap ALWAYS recommended
<or a suggested solution in case you do have noise? Unless you're flying
<behind a Rotax, you won't need the cap. If you are flying a PM alternator,
<then I presume one will begin with one of the appropriate Z-figures where
<this capacitor is always included. The XCOM is not the only accessory that
<will appreciate the presence of the extra filtering.
Bob
Bob
my understanding is the the big C is required to act as a sink/battery if the main
battery goes open circuit with the engine running. This will then prevent
the alternator going high.
Graham
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 |
|
--> AeroElectric-List message posted by: Fiveonepw@aol.com
Howdy Bob-
I am using one of these bilge blowers to ventilate the cabin of my RV:
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?resultCt=1&
jspStoreDir=wm51&catalogId=10001&productId=50224&keyword=1896950&y=20&x=12&
storeId=10001&ddkey=SiteSearch
If that mess don't work, try www.westmarine.com and product search pt#
1896950
Unit is fused from Main Bus on its own circuit through a SPST switch with
built-in LED indicator integrated into switch. After perhaps 20 hours of
operation (for the fan- over 150 hours on plane at the time) I began getting noise
in
audio system from the fan, but not all the time. I can't imagine that the
brushes have worn to the point of arcing any differently than when new, nor can
I explain intermittent noise. Usually when fan is turned on it's noisy,
sometimes it's as quitet as new. Is this a case where a capacitor across the fan
input leads should help & if so, what are criteria for determining cap value?
Would similar capacitor installed between fuse and ground instead of at the
fan have the same effect, and if not, why? Plane is Z-11, B&C L-40, generic VR,
LVWM & OVP, very quiet otherwise. Comm RG400 cable passes within 8 inches of
motor and is bundled for short distance with fan feed wire.
I followed the recent fan noise discussion, but difference here is one-speed
fan.
Thanks!
Mark Phillips, Columbia, TN
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:Battery Problem |
--> AeroElectric-List message posted by: "Frank Stringham" <fstringham@hotmail.com>
Hi to all
two cells in 24 volt battery boil over consistently, is over voltage relay
not protecting battery or is it a bad battery.
TIA
Frank @ SGU and SLC
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: Fox tails anyone? |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckollsr@cox.net>
Now Bob, there you go again with your floccinaucinihilipilification.
> > My airplane will have a high current B+ noise filter near the
> > alternator,
> > and one or more low current devices on the "avionics bus" or associated
> >with radios and intercoms wirings.
I certainly don't suggest that builders just add foxtails and flame decals
on the side of their cowling or Transorbs without reason, but I do think
your design idiom is not the way I will build my airplane.
My posting on filters is in reaction to inherently poor design in many light
aircraft electrical systems. Now many who just swamp the powerline with a
big cap will do fine. The use of the proper fitering is simply engineering
aesthetics. But I've flown in areas where the nearest station was not much
closer than the COSPAS-SARSAT satellite. A few bucks to keep the bus noise
down would be money well spent.
Your posting of the scope shots from your '95 Safari are instructive. If
that were my aircraft electrical system I would take some steps (but not a
lot) to quiet it down--merely for the reason that the noise introduces some
measurable reduction of performance in other electronic devices, and device
I haven't even installed yet, or devices that haven't even been invented
yet.
Now, if I were involved in reducing the noise to some standard and on a
contract, I wouldn't spend a minute trying to make it any better than it had
to be. This would be a waste of time--and in the engineering
vernacular--nuts.
So Bob---Let it be resolved that YOU think much of the details that I like
to look at are unnecessary. AND I'M SURE YOU'RE CORRECT. But which ones of
the many, are really reasonable insights and might advance the art? Do you
know?
And Paul Messinger keeps telling me, "One size doesn't fit all." And he's
perfectly right too.
But my concerns and my designs are often exploratory in nature--and that is
often how the world progresses. My designs incorporate shi-shi fru-fru
stuff, because I don't know what environment the device will see--and by
adding a transorb across the power inputs, I express the perhaps futile hope
that a lightning strike or other untold event MIGHT NOT kill it.
You call these "prophylactic measures"? Well, I say "a prophylactic, in time
save nine".
Please don't spend too much time on a reply. I only read six hours a day and
I'm near my limit today.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
America is a nation that conceives many odd inventions for getting somewhere
but it can think of nothing to do once it gets there.
--Will Rogers
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: Fox tails anyone? |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Hi Bob,
A good discussion.
Question below..
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
> <nuckollsr@cox.net>
>
>
>>
>> > My airplane will have a high current B+ noise filter near the
>> alternator, and one or more low current devices on the "avionics
>> bus" or associated
>> with
>> > radios and intercoms wirings.
>
>
> A few weeks ago, we had some discussions about the value
> of applying certain prophylactic measures to the installation
snip
> as recommended by the radio's manufacturer. I suggested
> that this requirement made sense for small aircraft with
> single-phase, PM alternators where the rectified output
> was VERY trashy. Most accessories would benefit from
> having the large capacitor added to the battery in terms
> of overall system noise reduction. Indeed, this capacitor
> was shown in all Z-figures illustrating PM alternator
> installations.
>
>
I wonder if the single-phase PM alternators (without big cap) meet the mil
standard (if there is one) for suppliers of electrical energy. If you
have one of these alternators and expect to power any avionics with it, it
only makes sense to install whatever is necessary (in terms of filters) to
meet the DO/mil standard. If you're just going to run some strobes and
nav lights, it probably doen't make any difference.
Do you have any scope shots of the output of one of these devices?
snip
Regards,
Matt-
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: | LM-317 & Noise Filtering |
--> AeroElectric-List message posted by: "J. Mcculley" <mcculleyja@starpower.net>
Request to Eric Jones:
I've used the LM-317 family of chips for voltage regulation but don't
understand how they would be wired for noise filtering. Can you
describe the circuitry appropriate for this purpose? Thanks.
Jim McCulley
Noise free Tailwind--but still a student!
> A really robust and useful filter that is hardly ever used is an LM317
> voltage regulator (or better yet some of its newer sisters). These voltage
regulators can do a much better filtering job than a pound of
capacitor and
inductor, especially at audio frequencies.
Eric Jones
>
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: AeroElectric-List Digest: 19 Msgs - |
10/03/05
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
10/03/05
At 11:10 AM 10/4/2005 +0100, you wrote:
>--> AeroElectric-List message posted by: Graham Singleton
><graham@gflight.f9.co.uk>
>
><<I'm pretty certain that the XCOM (like it's predecessor in the market -
> < Microair 760) will work just fine on typical light aircraft bus fed by
> <an automotive alternator. Many ultra-light owners like these tiny
> <radios too and they're almost always fitted with PM alternators that
> <are NOISY without additional filtering.
>
> <Check the instructions carefully, is the large cap ALWAYS recommended
> <or a suggested solution in case you do have noise? Unless you're flying
> <behind a Rotax, you won't need the cap. If you are flying a PM
> alternator,
> <then I presume one will begin with one of the appropriate Z-figures where
> <this capacitor is always included. The XCOM is not the only accessory
> that
> <will appreciate the presence of the extra filtering.
>
> Bob
>
>Bob
>my understanding is the the big C is required to act as a sink/battery if
>the main battery goes open circuit with the engine running. This will then
>prevent the alternator going high.
>Graham
Is that what XCOM says? Again, the capacitor is a great
adjunct to battery-less operation of a PM alternator . . .
and much less so for an automotive alternator. It would be
out of character for XCOM (or anyone eles) to make
recommendations for electrical system power generation.
Is this in their instruction manuals or anything I can
access on the 'net?
Bob . . .
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: RE:Battery Problem |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 09:13 AM 10/4/2005 -0600, you wrote:
>--> AeroElectric-List message posted by: "Frank Stringham"
><fstringham@hotmail.com>
>
>Hi to all
>
>two cells in 24 volt battery boil over consistently, is over voltage relay
>not protecting battery or is it a bad battery.
What is your bus voltage while this is happening? The fact that only
two cells of the 12 are affected suggests failures in those cells only.
A generalized OV condition would be expected to affect all cells the
same way.
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: Fox tails anyone? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 11:30 AM 10/4/2005 -0400, you wrote:
>--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
>
>
>--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
><nuckollsr@cox.net>
>
>Now Bob, there you go again with your floccinaucinihilipilification.
>
> > > My airplane will have a high current B+ noise filter near the
> > > alternator,
> > > and one or more low current devices on the "avionics bus" or associated
> > >with radios and intercoms wirings.
>
>I certainly don't suggest that builders just add foxtails and flame decals
>on the side of their cowling or Transorbs without reason, but I do think
>your design idiom is not the way I will build my airplane.
>
>My posting on filters is in reaction to inherently poor design in many light
>aircraft electrical systems. Now many who just swamp the powerline with a
>big cap will do fine. The use of the proper fitering is simply engineering
>aesthetics. But I've flown in areas where the nearest station was not much
>closer than the COSPAS-SARSAT satellite. A few bucks to keep the bus noise
>down would be money well spent.
>Your posting of the scope shots from your '95 Safari are instructive. If
>that were my aircraft electrical system I would take some steps (but not a
>lot) to quiet it down--merely for the reason that the noise introduces some
>measurable reduction of performance in other electronic devices, and device
>I haven't even installed yet, or devices that haven't even been invented
>yet.
"Measurable" does not translate to "perceivable" or even "deleterious."
I saw some noise traces taken from Space Shuttle busses and they were
awesome
sights to behold. They didn't even meet Mil-Std-704! Elegant engineering
is a process of trade-offs with a goal of optimizing return on
investment and building customer confidence in your abilities. If
my customer's machines were carrying any 'lectric "foxtails" with
my name on the drawings, I should be summarily dismissed.
>Now, if I were involved in reducing the noise to some standard and on a
>contract, I wouldn't spend a minute trying to make it any better than it had
>to be. This would be a waste of time--and in the engineering
>vernacular--nuts.
>
>So Bob---Let it be resolved that YOU think much of the details that I like
>to look at are unnecessary. AND I'M SURE YOU'RE CORRECT. But which ones of
>the many, are really reasonable insights and might advance the art? Do you
>know?
Based on my experience yes, I do know. I'm not suggesting you do anything
different in your airplane. I'm only cautioning others that not all
recommendations are supported by anything more than personal desires
on the part of the advisor. Unless the advice is founded on
data or a real problem solving experiment one is justified in being
skeptical and adopting a wait-and-see policy as opposed to adopting every
bit of advice 'cause it sounds good and made the advisor feel good.
>And Paul Messinger keeps telling me, "One size doesn't fit all." And he's
>perfectly right too.
Never suggested it does . . . I think it was Greg Richter who marched
off down that path.
>But my concerns and my designs are often exploratory in nature--and that is
>often how the world progresses. My designs incorporate shi-shi fru-fru
>stuff, because I don't know what environment the device will see--and by
>adding a transorb across the power inputs, I express the perhaps futile hope
>that a lightning strike or other untold event MIGHT NOT kill it.
I understand how your concerns can grow in proportion to lack of
data and experience. Please do whatever is necessary to achieve your
personal comfort goals. I'm only suggesting to 1300 other readers
that their comfort levels need not be lock-stepped with anyone else's
especially where there is no data to support the comforting hypothesis.
>You call these "prophylactic measures"? Well, I say "a prophylactic, in time
>save nine".
>
>Please don't spend too much time on a reply. I only read six hours a day and
>I'm near my limit today.
Just over 3 minutes . . . and I don't expect an answer.
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: LM-317 & Noise Filtering |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: "J. Mcculley"
<mcculleyja@starpower.net>
>Request to Eric Jones:
>I've used the LM-317 family of chips for voltage regulation but don't
>understand how they would be wired for noise filtering. Can you
>describe the circuitry appropriate for this purpose? Thanks. Jim McCulley
>Noise free Tailwind--but still a student!
>> A really robust and useful filter that is hardly ever used is an LM317
>> voltage regulator (or better yet some of its newer sisters). These
>> voltage
>> regulators can do a much better filtering job than a pound of
>>capacitor and inductor, especially at audio frequencies. Eric Jones
Jim,
The LM317 has 80 dB of ripple rejection built right in--because ripple is
just a variable voltage. It's not ideal--since fast op amps and active
filters do the job better--but compared to a big electrolytic cap and
inductor it weighs far less and has no altitude or aging problems. It will
handle 1.5 amps, and a couple more minor parts makes it a more versatile and
convenient choice for some applications.
A real engineer would say, "Why bother?" and point out some other simple
approaches But if you have an LM317 and a noise problem and only have to
filter an amp. Hey...it works well.
For those interested see: www.ixys.com/t03232kb.pdf
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
(508) 764-2072
"Beaten paths are for beaten men."
-Eric A. Johnston
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: | Firewall penetrations |
--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" <frank.hinde@hp.com>
Hello All,
Starting to think about the above subject seriously and spent some time
in the local hardware store looking for a way to provide a quick,simple
lightweight way to make a fire resistant hole in the 'wall.
So I found these metal conduit adaptors for electrical panels, the ones
with a single screw on on side.
They come in almost any size, are lightwight and have a threaded ring
which secures them to the wall... A dab of hi strength locktite will
required to secure the threads.
They are about 1.5 inch long that allows you to pack the free space with
fire sealant, and you could also push an additional short length of
firesleeve tube over the end secured with hose clamps if you so desired.
Best part they cost less than a buck each.
For control cables there are the NMB connectors which basically clamp
Romex for strain relief going into an electric panel. The neat thing
about these is they come with a metal sheild that pretty much covers the
unused part of the opening. They don't have the length of the above
conduit adaptors but they are sure better than a plastic snap bushing!!
Does this sound like a plan???
Frank
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: Firewall penetrations |
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
Are they steel or low melting temp "white" metal?
The steel or stainless steel towel rack/grab bars as per the
Aeroelectric Connection works well for efi systems with lots of wires.
Ken
Hinde, Frank George (Corvallis) wrote:
>--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" <frank.hinde@hp.com>
>
>Hello All,
>
>Starting to think about the above subject seriously and spent some time
>in the local hardware store looking for a way to provide a quick,simple
>lightweight way to make a fire resistant hole in the 'wall.
>
>So I found these metal conduit adaptors for electrical panels, the ones
>with a single screw on on side.
>
>They come in almost any size, are lightwight and have a threaded ring
>which secures them to the wall... A dab of hi strength locktite will
>required to secure the threads.
>
>They are about 1.5 inch long that allows you to pack the free space with
>fire sealant, and you could also push an additional short length of
>firesleeve tube over the end secured with hose clamps if you so desired.
>
>Best part they cost less than a buck each.
>
>For control cables there are the NMB connectors which basically clamp
>Romex for strain relief going into an electric panel. The neat thing
>about these is they come with a metal sheild that pretty much covers the
>unused part of the opening. They don't have the length of the above
>conduit adaptors but they are sure better than a plastic snap bushing!!
>
>
>Does this sound like a plan???
>
>Frank
>
>
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: | Firewall penetrations |
--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" <frank.hinde@hp.com>
Very good question...I assumed they were galvanised steel...I'll hit
them with a welding torch to be sure
Frank
Do not archive
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ken
Subject: Re: AeroElectric-List: Firewall penetrations
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
Are they steel or low melting temp "white" metal?
The steel or stainless steel towel rack/grab bars as per the
Aeroelectric Connection works well for efi systems with lots of wires.
Ken
Hinde, Frank George (Corvallis) wrote:
>--> AeroElectric-List message posted by: "Hinde, Frank George
>--> (Corvallis)" <frank.hinde@hp.com>
>
>Hello All,
>
>Starting to think about the above subject seriously and spent some time
>in the local hardware store looking for a way to provide a quick,simple
>lightweight way to make a fire resistant hole in the 'wall.
>
>So I found these metal conduit adaptors for electrical panels, the ones
>with a single screw on on side.
>
>They come in almost any size, are lightwight and have a threaded ring
>which secures them to the wall... A dab of hi strength locktite will
>required to secure the threads.
>
>They are about 1.5 inch long that allows you to pack the free space
>with fire sealant, and you could also push an additional short length
>of firesleeve tube over the end secured with hose clamps if you so
desired.
>
>Best part they cost less than a buck each.
>
>For control cables there are the NMB connectors which basically clamp
>Romex for strain relief going into an electric panel. The neat thing
>about these is they come with a metal sheild that pretty much covers
>the unused part of the opening. They don't have the length of the above
>conduit adaptors but they are sure better than a plastic snap
bushing!!
>
>
>Does this sound like a plan???
>
>Frank
>
>
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: Firewall penetrations |
--> AeroElectric-List message posted by: "Richard E. Tasker" <retasker@optonline.net>
I believe you will find these are zinc or some similar alloy, but do
test them and let us know.
Dick Tasker
Hinde, Frank George (Corvallis) wrote:
>--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" <frank.hinde@hp.com>
>
>Very good question...I assumed they were galvanised steel...I'll hit
>them with a welding torch to be sure
>
>Frank
>
>Do not archive
>
----
Please Note:
No trees were destroyed in the sending of this message. We do concede, however,
that a significant number of electrons may have been temporarily inconvenienced.
----
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: | Seeking Dan Checkoway |
--> AeroElectric-List message posted by: "Bret Smith" <smithhb@tds.net>
When will your RVProject site be back online?
Sorry for the off-topic. Do Not Archive
Bret Smith
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: LM-317 & Noise Filtering |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
>
>Jim,
>
>The LM317 has 80 dB of ripple rejection built right in--because ripple is
>just a variable voltage. It's not ideal--since fast op amps and active
>filters do the job better--but compared to a big electrolytic cap and
>inductor it weighs far less and has no altitude or aging problems. It will
>handle 1.5 amps, and a couple more minor parts makes it a more versatile and
>convenient choice for some applications.
>
>A real engineer would say, "Why bother?" and point out some other simple
>approaches But if you have an LM317 and a noise problem and only have to
>filter an amp. Hey...it works well.
With limitations. See:
http://cache.national.com/ds/LM/LM117.pdf
A popular part stocked by Radio Shack is the LM317T (TO-220
plastic power package). The middle plot on the right side of
page 6 describes a feature called "Dropout Voltage" and illustrates
how it varies with temperature and operating current. Assuming you
want to operate at say 500 milliamps and your chip will never be
called to function at or below 0C, then we read from the chart
that dropout voltage is about 1.8 volts.
Assuming a bus voltage of 13.8 volts minimum and a noise
component of say 1 volt peak-to-peak, then the MAXIMUM
expected regulated output from the LM317 is 13.8 minus
1.8 minus 0.5v or 11.5 volts. Another way of stating this
operating characteristic is to say that the input voltage
cannot be allowed to drop any closer than 1.8 volts of the
output setpoint which must INCLUDE the negative most going
excursion due to noise.
Generally speaking, three-terminal regulators can be used
to great advantage to provide a noise free power source for
accessories that operate substantially below bus voltage.
This is why the max setpoint for our three-terminal reguator
based dimmer is designed to 12 volts. The audio isolation
amplifier described at
http://www.aeroelectric.com/Catalog/AEC/9009/9009-700E.pdf
operates at 8.7 volts . . . well below the incoming
bus voltage.
One can purchased "low dropout" devices that work down to
a few hundred millivolts differential but you must always
set for an output voltage low enough to prevent the negative
going component of noise does not go below the allowable
dropout value.
As a general rule, these devices are not well suited for
reducing bus noise to accessories that are designed to
operate directly from bus voltages. They work quite well
in situations like those illustrated.
Bob . . .
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! --
|