I have a 24 volt linear actuator that needs control from a Futaba radio. I have a channel on the radio that is three position. I want to have forward, reverse and stop. I tried a Electronic Model Systems/ Jomar dual electronic switch. The switch will not directly work with 24 volts so I used two power relays. The design when benched using 12 volts worked fine. It didn’t work in the robot because the switch uses mosfets and not relays, seems to be a problem using a common ground from the Futaba and when I simply stepped down the voltage by running a second wire from the 12 volt batteries.
I’ve not been able to find a solution to this and I’m surprised that no one makes a heavy duty switch in this configuration. The dual battle-switch from DE was another thought but it has no center position where both relays are off.
The transmitter is likely providing a ~500us (up to about 1000us) pulse when in the down position, a 1500us pulse when centered and ~2000 (to2500) pulse when flipped up.
You could use a standard RC motor controller; these accept RC input and 1500us is “stopped”. robotshop.com/en/brushed-mot … llers.html
There is no positioning possible; you control direction only. You would need to program your microcontroller for maximum pulse for that switch in order to vary the speed.
If you only wanted very simple fwd/off/bkwd control, you could arrange two micro switches to be actuated by a cam on an R/C servo.
I did this for a high-voltage control in a test fixture. Select two positions to run the servo to, and have it actuate one switch or the other (or none in between).
I think you’re right Alan and this morning I took a small servo and milled out a part to hold the servo and the two cherry switches. It seemed easier to use an electronic switch but that’s just not the case. I’m very surprised that something like the double-battle-switch doesn’t have some adjustability.
If you have two battle switches, then they can be connected to mimic a double throw relay, but you have to make certain that both don’t get turned on at the same time. I like the microswitrches.
The battle switch only turns on when the channel goes to one side. For a reversing DC motor you need three positions for two relays and one relay is DPDT while the second is SPDT.
Well just to finish this off with how and what I did. I ditched the idea of doing this electronically. I picked up two SPDT snap action switches that were rated for 15 amps and wired them directly to the actuator motor so no longer did I have a need for relays. I mounted the switches to a milled piece of aluminum with a servo in the center and a shaped servo-horn. Connected it and it works as it should.
With the SPDT you just connect the common of both switches to the leads of the motor. You then connect the two NC connections to negative and the NO sides to positive.
This configuration also has the added benefit of shorting the motor when in the off position which might be useful when you need to stop the motor quickly.
