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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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 Posted: Sun Oct 02, 2011 8:13 am Post subject: Noisey Power Supplies. |
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I sell some LED tail lights and used to supply them with commercial constant current supplies--Power Pucks from Luxdrive. But making them quiet was another matter. I know Bob N. put together a fix for these. It would be interesting to see how they worked in the field...I frankly never had any luck, but I did autopsy a unit to see why it was so noiseyand found it was simply a matter of poor design. For a while I considered re-engineering them and selling the identical product, but there was no profit in it.
So I changed them all to tomb-silent LM317-based constant current supplies and never heard another peep. I will send you the documentation for a Roll Your Own version (attached), and am considering making a slicker version later (also attached).
For the beginner who might wonder why one doesn't use a simple resistor, here's why:
The tiny LEDs used as indicators use 20 milliamps. So running them on 14.5V requires a R=(14.5V-2Vf)/0.020=~625 ohm resistor. The resistor power is .020 x 0.020 x 625=W=0.25 or a 1/4W resistor (minimum).
But the numbers start getting difficult with a 1 Amp LED: R=(14.5-3.2Vf)/1=
11.3 ohm resistor. So far so good. The resistor power is 1 x 1 x 11.3=11.3 Watts (minimum). (you can use 10 or 12 and recalculate. You should use a higher wattage resistor, too). The resistor is the size of your finger, not cheap, requires mechanical mounting and gets hot. You could still do it, but this is the limit of the olde-current limiting resistor technique.
The LM317 current-controller technique is in fact more expensive and larger and heavier than using a switching power supply, but not much, and it has the great advantage of being as quiet as a resistor...and you can build it yourself easily.
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Current Regulator.pdf |
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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mrspudandcompany(at)veriz
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sam.marlow
Joined: 25 Feb 2006
Posts: 99
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| Posted: Mon Oct 03, 2011 10:59 am Post subject: Noisey Power Supplies. |
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ROGER & JEAN CURTIS wrote:
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Mon Oct 03, 2011 12:28 pm Post subject: Re: Noisey Power Supplies. |
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Sorry, the second attachment was supposed to be deleted because I never referred to it. But here it is anyway. It is self explanatory.
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Canopy Latches for Bipolar LEDs.pdf |
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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Brantel
Joined: 23 Aug 2008
Posts: 53
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| Posted: Tue Oct 11, 2011 7:23 am Post subject: Re: Noisey Power Supplies. |
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Are you making and selling the PC board used in this design? If so, details?
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nuckolls.bob(at)aeroelect
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| Posted: Tue Oct 11, 2011 10:02 am Post subject: Noisey Power Supplies. |
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At 10:23 AM 10/11/2011, you wrote:
| Quote: |
Are you making and selling the PC board used in this design? If so, details?
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I presume we're talking about the filtered mounting
board for a BuckPuck. Yes, I have boards with filters
install and no BuckPuck . . . or complete assemblies
with 1A BuckPuck. I guess if you wanted a bare board,
I could acomodate that also . . . but buying filter
components in small quantities is probably not
cost effective. See the catalog page on my website.
Bob . . .
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Brantel
Joined: 23 Aug 2008
Posts: 53
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| Posted: Tue Oct 11, 2011 11:08 am Post subject: Re: Noisey Power Supplies. |
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No Bob, Sorry,
Talking about the one that Eric Jones posted a schematic and directions for in this post:
http://forums.matronics.com/viewtopic.php?t=84628
It is a design for a linear regulator instead of a switching regulator which is a little less efficient but does the job without all of the noise issues.
I already have two of yours...they work great!
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nuckolls.bob(at)aeroelect
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| Posted: Tue Oct 11, 2011 7:11 pm Post subject: Noisey Power Supplies. |
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At 02:08 PM 10/11/2011, you wrote:
| Quote: | --> AeroElectric-List message posted by: "Brantel" <bchesteen(at)hughes.net>
No Bob, Sorry,
Talking about the one that Eric Jones posted a schematic and directions for in this post:
http://forums.matronics.com/viewtopic.php?t=84628
It is a design for a linear regulator instead of a switching regulator which is a little less efficient but does the job without all of the noise issues.
I already have two of yours...they work great! |
Oh . . . if Eric doesn't have a board for the
LM317 version of a constant current generator,
I have a constant current board I'm doing for
a customer right now. It's based on a TO247
power mos-fet and is capable of offering constant
current values upwards of 3 amps.
[img]cid:7.1.0.9.0.20111011215915.0037fc80(at)aeroelectric.com.0[/img]
This board is about 1.3 x 1.4 inches. The power
fet heat sinks through an insulating washer.
Bob . . .
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