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rgf(at)dcn.davis.ca.us
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 Posted: Mon May 04, 2009 8:55 pm Post subject: Reducing RF noise for a Luxeon PowerPuck |
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I'm making some LED navigation lights. Being part Irish and stubborn I
decided to try the Luxeon PowerPuck
(http://www.luxeonstar.com/powerpuck-700ma-dc-led-driver-with-leads-p-27.php
) even though I also had Robert Nuckolls' filtered Buck Puck. Sure enough
the PowerPuck produces RF noise, measured by a hand-held Icom receiver.
Squelch has to be turned nearly all the way up to silence the receiver.
Now the PowerPuck data sheet
(http://www.leddynamics.com/LuxDrive/datasheets/2008B-PowerPuck.pdf) has a
specific fix for RF noise, a 220uf cap between the input leads (page 4). I
got the appropriate cap from Radio Shack and simply stuck it between the
input leads without shortening the cap's wires or soldering it. No
difference in RF noise.
At this point I can think of these options:
1. Replace the Luxeon PowerPuck with the filtered Buck Puck.
2. Replace the Luxeon PowerPuck with a resistor of appropriate wattage and
resistance.
3. Do nothing, maybe the RF noise isn't that bad.
4. Or, being part Irish and stubborn, try to filter the RF noise of the
Luxeon PowerPuck.
I'd like to try 4. a little more. What more can I do to filter the noise.
Would the caps and coils used to filter the Buck Puck work for the Luxeon?
Maybe use telephone wire (unshielded twisted pair)?
Thanks,
Ralph Finch
Davis, CA, USA
RV-9A QB SA
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rv(at)thelefflers.com
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| Posted: Tue May 05, 2009 2:43 am Post subject: Reducing RF noise for a Luxeon PowerPuck |
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Ralph,
I'm confused here. Why don't you just use the filtered unit that Bob K. has
designed? It seems that your #4 option is just re-inventing the wheel.
Bob
--
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rgf(at)dcn.davis.ca.us
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| Posted: Tue May 05, 2009 4:45 am Post subject: Reducing RF noise for a Luxeon PowerPuck |
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| Quote: | It seems that your #4 option is just re-inventing the wheel.
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Yes.
| Quote: | Why don't you just use the filtered unit that Bob K. has
designed?
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Part Irish and all stubborn. I probably will end up using
Nuckolls' filtered Buck Puck...but am curious why using
the capacitor as suggested by the manufacturer didn't seem
to have any effect on RF noise.
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jdubner(at)yahoo.com
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| Posted: Tue May 05, 2009 9:36 am Post subject: Reducing RF noise for a Luxeon PowerPuck |
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Ralph Finch wrote:
| Quote: | but am curious why using
the capacitor as suggested by the manufacturer didn't seem
to have any effect on RF noise.
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Ralph,
I don't have any specific knowledge of your parts but hey, this is the
Internet  And you said you are curious.
In spite of the manufacturer's recommendation, a 220 uF capacitor is
totally ineffective at reducing RF noise at VHF. And even if it was
effective, installing it with long leads would negate that. (The 220 uF
capacitor is recommended by the manufacturer is for another purpose).
My recommendation would be to solder a .001 uF (1000 pF) capacitor with
the shortest leads possible across the input and output of the module.
And keep all wiring as short as practical. Twisting the Vin positive
and negative leads would be good too.
--
Joe
Independence, OR
Aircraft Position: http://www.mail2600.com/position
Aircraft Track: http://www.mail2600.com/track
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Tue May 05, 2009 9:55 am Post subject: Re: Reducing RF noise for a Luxeon PowerPuck |
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I too, experimented with the PowerPuck to see what I could do about the noise. The big capacitor was a waste of time. I finally dissolved off the potting to study the problem and decided that it was just a poor design (Hey, even PCB designers have to start someplace). I was thus surprised when Bob N. decided to try to quiet it. I have not seen Aeroelectric feedback to see how successful the filter design was, but I personally doubt it was worthwhile.
There are better approached than to try to fix someone else's bad designs:
Try: www.Astrodyne.com for good designs for short money. Alternatively if you want a really quiet solution, build yourself a Linear current regulator using an LM317 or similar: www.periheliondesign.com/downloads/currentregulators.pdf
but you won't get the low current of the switcher design.
If you want to build LED position lights, see my article on the subject.
www.periheliondesign.com/downloads/redandgreenledpositionlights.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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echristley(at)nc.rr.com
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| Posted: Tue May 05, 2009 3:27 pm Post subject: Reducing RF noise for a Luxeon PowerPuck |
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Ralph Finch wrote:
| Quote: |
> It seems that your #4 option is just re-inventing the wheel.
>
Yes.
> Why don't you just use the filtered unit that Bob K. has
>
designed?
Part Irish and all stubborn. I probably will end up using
Nuckolls' filtered Buck Puck...but am curious why using
the capacitor as suggested by the manufacturer didn't seem
to have any effect on RF noise.
It's very possible that your "stick the leads to the contacts" was a
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very high resistance joint. The long leads could also act as antennae.
It doesn't take much radiated noise for it to be picked up only a few
feet away. RF can be nasty stuff to work with sometimes. It will often
do what it wants, before what you want.
--
http://www.ernest.isa-geek.org
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nuckollsr
Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS
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| Posted: Tue May 05, 2009 7:20 pm Post subject: Re: Reducing RF noise for a Luxeon PowerPuck |
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I too, experimented with the PowerPuck to see what I could do about the noise. The big capacitor was a waste of time. I finally dissolved off the potting to study the problem and decided that it was just a poor design (Hey, even PCB designers have to start someplace). I was thus surprised when Bob N. decided to try to quiet it. I have not seen Aeroelectric feedback to see how successful the filter design was, but I personally doubt it was worthwhile.
There are better approached than to try to fix someone else's bad designs:
Still out in California working a client's problem but thought I'd offer a response. I decided to try to "quiet it" because that was the task. Lots of folks had already purchased this product . . . it seemed a bit obtuse to say
"you bought a piece of junk . . . here buy my gizmo instead."
Further, one would be hard pressed to say that the PowerPuck did not perform as advertised . . . no place in the ads did I find a suggestion that they were recommended or declared suitable for use in aircraft.
We've sold several dozen of both the fully assembled power supplies and the -99 add-on filter for individuals who already had BuckPucks in hand.
Everyone who reported noise problems before adding the AEC filter reported a satisfactory reduction in noise afterward. I've got a DO-160 emissions test coming up in the lab for another customer in the next few weeks . . . I try to piggy-back the AEC product onto the testing effort and put real numbers to the observed successes. If anyone discovers that the products offered by AEC do not perform as advertised, it's my sincere expectation that they'll be returned for a refund . . . no such events have taken place at the time of this writing.
For those interested in a DIY version of our efforts, I'll suggest you download https://matronics.com/aeroelectric/Catalog/AEC/9051/9051-700A.pdf and get the component values off of page 4.
Bob . . . [/b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed May 06, 2009 6:53 am Post subject: Reducing RF noise for a Luxeon PowerPuck |
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| Quote: |
<rgf(at)dcn.davis.ca.us>
I'm making some LED navigation lights. Being part Irish and stubborn I
decided to try the Luxeon PowerPuck
(http://www.luxeonstar.com/powerpuck-700ma-dc-led-driver-with-leads-p-27.php
) even though I also had Robert Nuckolls' filtered Buck Puck. Sure enough
the PowerPuck produces RF noise, measured by a hand-held Icom receiver.
Squelch has to be turned nearly all the way up to silence the receiver.
|
Are you saying that the AEC version of a filtered BuckPuck still emitted
detectable
noise? If you're using a hand-held with a rubber-duck antenna as a
sniffer, then
understand that many devices . . . even DO-160 qualified devices may
demonstrate
detectable emissions at close range.
Remember that DO-160 says "reduce deleterious effects to some level
demonstrated to be adequate to the task." The acid
test is can you detect the BuckPuck's emissions from any of your
ship's systems. Using a hand-held as a sniffer is a useful diagnostic
tool but it's non-quantified and may have no practical relationship
to suitability of a completed installation.
| Quote: |
Now the PowerPuck data sheet
(http://www.leddynamics.com/LuxDrive/datasheets/2008B-PowerPuck.pdf) has a
specific fix for RF noise, a 220uf cap between the input leads (page 4).
I
got the appropriate cap from Radio Shack and simply stuck it between the
input leads without shortening the cap's wires or soldering it. No
difference in RF noise.
|
The electrolytic capacitor has no practical benefits at our particular
frequnecy of interest (VHF nav and comm). The components described
in the AEC9051 installation instructions are chosen for their efficacy
at VHF.
| Quote: |
At this point I can think of these options:
1. Replace the Luxeon PowerPuck with the filtered Buck Puck.
|
May not be necessary . . . does the un-filtered device cause you
problems in the cockpit?
| Quote: | 2. Replace the Luxeon PowerPuck with a resistor of appropriate wattage and
resistance.
|
The BuckPuck is more than a "resistor". It's a constant cujrrent power
supply
that maintaines lamp performance over a wide range of power input
conditions.
| Quote: | 3. Do nothing, maybe the RF noise isn't that bad.
|
Yes . . . see (1) above.
| Quote: | 4. Or, being part Irish and stubborn, try to filter the RF noise of the
Luxeon PowerPuck.
|
If noise IS an flight-ops problem, then it's not hard to whip it but
will take some time (education is almost never inexpensivfe).
| Quote: |
I'd like to try 4. a little more. What more can I do to filter the noise.
Would the caps and coils used to filter the Buck Puck work for the Luxeon?
Maybe use telephone wire (unshielded twisted pair)?
|
Wire treatments are NOT tools for the mitigation of radiated
or conducted noise. Shielding, twisting, routing, etc are
generally ineffectual things you do AFTER the horse is out of
the barn! FILTERS are the firewall for noise ingress/egress to
any proudct.
Bob . . .
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rgf(at)dcn.davis.ca.us
Guest
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| Posted: Wed May 06, 2009 7:59 am Post subject: Reducing RF noise for a Luxeon PowerPuck |
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I have bought, but not tested, the Buck Puck, either as-is or filtered.
What I was "testing" with the hand-held was the Luxeon PowerPuck,
unfiltered. Certainly far from scientific, but the only method I have. The
two other devices I was concerned about--power supplies for an HID landing
light and a strobe--produced detectable, but far less, noise on the
handheld.
All of this is just with a single wing. No fuselage, it's miles away stored
in a hangar.
Bob and others, thanks for your very interesting replies. At this time I'm
going to "test" Bob's filtered Buck Puck with my handheld. Assuming that it
produces little static, I can then use that or just a resistor in series. I
may go the latter, reserving the more expensive filtered Buck Puck for the
cockpit driving white and red LEDs where I will take advantage of the Buck
Puck's 5v reference signal to make a variable strength light source.
Ralph Finch
--
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