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Hopperdhh(at)aol.com
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 Posted: Fri Aug 04, 2006 5:38 am Post subject: Aero-Electric List: MPJA Speed Control |
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Ernest,
Apparently this speed control/dimmer uses a PWM (pulse width modulation)0 technique to dim the LEDs. LEDs are very fast responding unlike an0 incandescent bulb which stays hot between pulses. You can get some weird0 effects with this kind of dimming. When you glance across the panel you0 can probably see the lights as a series of bright spots rather than solid0 lights. In older calculators with 7 segment LED readouts you could move0 the calculator downward across your field of vision and get a stairstep effect0 due to multiplexing of the display. In other words, only one of the0 numbers is on at any given time. This requires less circuitry to drive all0 of the display segments. In a panel dimmer it conserves power, and the0 dimmer dissipates far less power.
I have yet to see an aircraft radio with LED displays that uses0 multiplexing for the display, probably to avoid the effect described0 above. I would think that a linear dimmer circuit would be a better choice0 for an aircraft panel. I am very happy with the A and T Labs K11 Panel0 Dimmer although I substituted a less massive heat convector. Just my0 opinion, YMMV.
http://www.a-and-t-labs.com/K11_Dimmer
Dan Hopper
RV-7A
In a message dated 8/4/2006 9:06:28 A.M. Eastern Daylight Time,0 echristley(at)nc.rr.com writes:
AeroElectric-List Digest Server wrote:
| Quote: | Hi0 Ernest,
Yes, I'm using the MPJA pwm speed controller for dimming0 LED's. In the
attached jpg. you can see the string of led's0 across the top of my panel
which are controlled by a single MPJA speed0 controller. I too
repositioned the potentiometer with a remote0 unit of higher quality. All
of my circuits were configured from the0 manufacturer to operate on 12v
as the MPJA pwm speed controller is0 designed to operate a 12v motor.
Works great with no noticeable0 flicker.
Mark S.
Thanks,0 guys. As often happens, I must've done something wrong. I'll0
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need to double check again that I got all the resistors in the right0
places, and then schedule some time with the O-scope.
BTW, just for0 the record, I drilled a second 3/32" anti-rotation hole
for the supplied0 potentiometer so that I could stick it through in the
other0 direction. I did this AFTER checking that it was a simple,0
center-tapped pot. This lets all the jelly bean parts go inside0the0
supplied box (drill ventilation holes) which I can then bolt up to the0
backside of my panel with the control knob sticking through.
--0
,|"|"|, 0 Ernest Christley 0 |
----===<{{(oQo)}}>===---- Dyke Delta Builder 0 |
o| d |o 0 http://ernest.isa-geek.org 0 ========================== Use0 lities0 Day0 0 0
-->0 ================================================== - NEW MATRONICS LIST WIKI -
_-=0 sp;0 0 ->0 =========================p;0 - List Contribution Web Site0 0 0 ==================================================
[/quote]
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brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
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| Posted: Fri Aug 04, 2006 6:59 am Post subject: Aero-Electric List: MPJA Speed Control |
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On Aug 4, 2006, at 9:31 AM, Hopperdhh(at)aol.com wrote:
| Quote: | Apparently this speed control/dimmer uses a PWM (pulse width
modulation) technique to dim the LEDs. LEDs are very fast
responding unlike an incandescent bulb which stays hot between
pulses. You can get some weird effects with this kind of dimming.
|
Persistence of vision averages the on/off time to effect the dimming
of the LEDs. The average energy that the LED emits is reduced so that
the eye has fewer photons to respond to.
So, yes, PWM will dim LEDs too.
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry
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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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Hopperdhh(at)aol.com
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| Posted: Fri Aug 04, 2006 7:15 am Post subject: Aero-Electric List: MPJA Speed Control |
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In a message dated 8/4/2006 11:05:15 A.M. Eastern Daylight Time,0 brian-yak(at)lloyd.com writes:
On Aug0 4, 2006, at 9:31 AM, Hopperdhh(at)aol.com wrote:
| Quote: | Apparently this0 speed control/dimmer uses a PWM (pulse width
modulation)0 technique to dim the LEDs. LEDs are very fast
responding0 unlike an incandescent bulb which stays hot between
0 pulses. You can get some weird effects with this kind of0 dimming.
|
Persistence of vision averages the on/off time to effect the0 dimming
of the LEDs. The average energy that the LED emits is0 reduced so that
the eye has fewer photons to respond to.
So,0 yes, PWM will dim LEDs too.
Brian Lloyd 0 [/quote]
Brian,
You didn't get the point of my message. Persistence of the eye does0 what you say, until you move your eyes. Then your eyes are fooled, and you0 see dots (or lines) instead of steady lights.
Dan
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brian
Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA
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| Posted: Fri Aug 04, 2006 12:42 pm Post subject: Aero-Electric List: MPJA Speed Control |
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On Aug 4, 2006, at 11:11 AM, Hopperdhh(at)aol.com wrote:
| Quote: | Brian,
You didn't get the point of my message. Persistence of the eye
does what you say, until you move your eyes. Then your eyes are
fooled, and you see dots (or lines) instead of steady lights.
|
That is true when looking at the LEDs themselves. But if your LEDs
are working as flood lights, the lighted area will not do what you
are suggesting as the light covers such a large area.
Brian Lloyd 361 Catterline Way
brian-yak AT lloyd DOT com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
— Antoine de Saint-Exupéry
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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Hopperdhh(at)aol.com
Guest
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| Posted: Fri Aug 04, 2006 4:09 pm Post subject: Aero-Electric List: MPJA Speed Control |
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Brian,
Oh. I'll have to give it a try. I can see that covering a large0 area may change things. I was thinking of my own panel where I have two0 bright white LEDs in the artificial horizon light bar connected to the0 panel dimmer. With PWM, I could just imagine seeing multiple AHs as I0 scanned the panel! Or if I had a row of LEDs on the underside of the glare0 shield, seeing lights dancing all over the inside of the airplane as I look0 around outside at night.
do not archive
Thanks,
Dan
In a message dated 8/4/2006 7:20:02 P.M. Eastern Daylight Time,0 brian-yak(at)lloyd.com writes:
-->0 AeroElectric-List message posted by: Brian Lloyd0 <brian-yak(at)lloyd.com>
On Aug 4, 2006, at 11:11 AM,0 Hopperdhh(at)aol.com wrote:
| Quote: | Brian,
You didn't get the0 point of my message. Persistence of the eye
does what you0 say, until you move your eyes. Then your eyes are
fooled,0 and you see dots (or lines) instead of steady lights.
|
That is true0when0 looking at the LEDs themselves. But if your LEDs
are working as0 flood lights, the lighted area will not do what you
are suggesting0 as the light covers such a large area.
Brian Lloyd 0 3610 Catterline Way
brian-yak AT lloyd DOT com 0 Folsom, CA 95630
+1.916.367.2131 (voice) 0 +1.270.912.0788 (fax)
I fly because it releases my mind0 from the tyranny of petty things . . .
— Antoine de0 =================================================== Use0 lities0 Day0 0 0
-->0 ================================================== - NEW MATRONICS LIST WIKI -
_-=0 sp;0 0 ->0 =========================p;0 - List Contribution Web Site0 0 0 ==================================================
[/quote]
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