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Looking for help on an electrical power question

Started by Kaellis991, December 03, 2021, 07:37:33 AM

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I am working on a partial panel cockpit and just received an INOP autocontoller IIIB autopilot head unit. It has the two rocker switches on either side of the rotary roll control knob.

I want to use the switches to connect to my Arduino for the A/P on/off and the heading switch. It's easy enough to connect the momentary switches to the board. But to keep the momentary switches in the closed position the top of the  rocker levers are held in the on position by a small 3/4" diameter electromagnet attracting a metal plate on the top back of the rocker. I've been able to energize the magnets to hold the rocker lever against the switch plunger using two 9v batteries in series producing 18v. The resistance through the windings is 148 ohms.

Is there a better way to power these electromagnets? 18 volts of power will work. Two 6 volt batteries in series will not work.


Would this work for you?

3V - 24V 1.5A 36W Adjustable DC Power Supply Adapter Speed Control Volt Display with Variable 8 Plugs and 1 Polarity Reverse Cable Cord https://www.amazon.com/dp/B07QVXYBDC/ref=cm_sw_r_cp_api_glt_fabc_6830WWYYQYEDN22SH4T9?_encoding=UTF8&psc=1

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I don't know if it would but for only $20 I'll give it a try.

Jason L

Weren't a lot of those systems 24v?  Could look at coupling a PS like Jon mentioned with a USB relay card that would help you with the interfacing.


The aircraft power is 12 volt or course. Are you saying that the autopilot circuitry may step up the voltage to 24v to energize the magnets? Would the USB relay be used in some way to turn off the power to the magnets when the switches are placed in the off position?  That is how the circuitry in the autopilot works. But since I can't really use the defunct circuit board for my flight sim I would have to design my own setup to accomplish that. But my electronics knowledge is very limited and I don't have a clue how that would be done.

Jason L

I have an older OEM 727 throttle that was modified to work as a 737 (one throttle lever removed).  When I was originally working on interfacing it, it had a magnetic brake for the trim wheel, I needed to supply 24v to get it to work properly.  What I did was had 24v to a USB relay card, which could then have logic set to either enable or disable it.  Did it this way since most interface boards can either not handle that type of voltage, or the necessary amperage.

Hope that helps clarify.


I bought the PS that John mentioned and found that it works for energizing the electromagnets from 24v down to around 5v. Right around 5 the magnet can't hold the rocker plate.

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