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12-19-2018, 07:38 PM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,277
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Question on wiring Rheostat
I will be using a 5 watt rheostat for my instrument light dimming (250 mA lighting load). My question is do I need to ground the other end terminal. I will bring 12 V on one end and feed the dimmer bus via the center feed. Just wondering if I need to ground the other end. I am guessing that I don't, but not sure and haven't tested yet.
Larry
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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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12-19-2018, 10:15 PM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,277
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Quote:
Originally Posted by rv7charlie
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Thanks. That is what I thought.
Larry
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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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12-19-2018, 10:37 PM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,277
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Well I did some testing and realized that as a variable resistor it only reduces current and not voltage. I had hoped to use the same unit to dim the indicators and the EFIS / avionics and the latter need variable voltage to control dimming. Turns out that if I set it up as a voltage divider it actually dims the indicator lamps even better. They are 12v LED units with built in resistors.
Most of instruments have adjustable scales to match dimming to voltage, so this should work well.
Thought I would share the outcome.
Larry
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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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12-20-2018, 05:59 AM
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Join Date: Aug 2014
Location: Bowie MD
Posts: 886
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LEDs are dimmed using a PWM board, not a rheostat. They are cheap, just google PWM motor controller (not LED controller) - about $10. I use one for all my interior LED strips......
This is what I used... https://www.amazon.com/RioRandTM-Upg...tor+controller
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Mani
Busby MustangII (FoldingWing) Pending DAR.
Don't be a hater; I'm a cousin with thin wings! 
N251Y (res)
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12-20-2018, 08:18 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,277
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Quote:
Originally Posted by maniago
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The LED indicators in my 6A are also dimmed with voltage reduction. It works when the LED units have resistors installed for running on 12v. May not be optimum, but it works.
Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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12-20-2018, 08:37 AM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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It depends on the LED product and how they designed the current regulator, if it has such.
There are two basic types - constant current or constant voltage.
The LED system I used, Luxeon Star, has an external regulator available with an input for a simple pot for control. If your product has internal regulation, it?s best to know what the manufacturer wants to see for dimming.
Most publish this.
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Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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