I am working on a project to connect a military surplus remote-controlled spotlight to a joystick. The light came off an MRAP and the joystick is a turret control joystick retrofitted with arcade joystick guts. Supply voltage is 24v DC from a HMMWV's power system.

The joystick contains four single pole momentary switches. Because of the design of the joystick, switches opposite of each other (left/right and front/back) cannot be closed at the same time.

The light is controlled by two pairs of motor leads. One pair controls elevation and the other rotation. Applying 24v to the left/right pair turns the light in one direction (i.e. right). When the polarity is reversed, the direction of movement is reversed (i.e. left). The elevation motor works the same way with one polarity moving the light's point of aim up and the opposite polarity moving it down .

I've noodled on this a fair bit, but so far have been unable to come up with a circuit that will allow me to reverse the polarity of the motor control leads using only the SP switches that are in the joystick. I'm guessing that my SP switches may have to close a DP relay, but was hoping for something simpler.

I have a moderate familiarity with analog circuits, but that's mostly from experience with garden railroading. Any advice or suggestion would be greatly appreciated.

 

Welcome to AAC!
Are the joystick switches capable of carrying the high start-up current that the motor draws?
What is the rated running current of the motor?
If the switches can carry the full current then here's an option :-

You might need to add spike suppression components. Choice of MOSFETs would depend on motor current/voltage.

 

Are the joystick switches SPST or SPDT?

IF (as above) the switches can handle the motor current
AND IF the switches are SPDT
THEN you might be in luck
ELSE the switches control four external SPDT relays (two per motor) or two H-bridges (one per motor) of power MOSFETs

ak

 

Welcome to AAC!
Are the joystick switches capable of carrying the high start-up current that the motor draws?
What is the rated running current of the motor?

The switches are 10A cherry switches, so they should be fine. I don't have the motor(s) specs, but according to the manf. web site they're 0.16A @ 24V. These are very small motors that are just moving a 24v spot that's about the size of an automotive headlight.

 

With a maximum current of 10A, it can be full-size micro switches with change over contacts.

If true, then the circuits of the two directions can be something like this sketch:

 

Don't let the Motor Currents flow thru' the Joystick switches - for 2 main reasons:
* The switches are most likely not rated for the motor current.
* The Joystick is most likely to be placed some distance away from the Motors and there will be voltage drops on the connecting leads.

I'd go with Alec_t's idea.

 

Thanks for all the replies so far. You've provided some really useful info.

 

If you can replace the SP switches with DP switches, you can use Kjeldgaard 's circuit.

Even if you have to remove some plastic.

 

The switches are 10A cherry switches, so they should be fine. I don't have the motor(s) specs, but according to the manf. web site they're 0.16A @ 24V. These are very small motors that are just moving a 24v spot that's about the size of an automotive headlight.

10A DC? Believe that’s the running current requirement... how about the startup current? And unless there’s a significant dead zone when reversing between direction, there may be a significant current drain there as well.

 

The running current is one hundred and sixty milliamps

 

Just an update... Got it working thanks to the advice from the forum