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R/C DPDT switch?

2712 Views 8 Replies 7 Participants Last post by  toddalin
I want to control a Double-pole/Double-Throw switch using an analog R/C transmitter.  I guess I could just connect a servo to the hand-toggle of the switch, but I'd rather use some sort of electronic switch that can do an On/Off/On sequence just like the DPDT mechanical switch.

Is there anything commercially available that will do this?  I really don't want to buy IC chips and resistors to build one on a circuit board, I just want an R/C DPDT switch.
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It might help if you told us what you want the DPDT switch to do.

There is likely to be some way to do what you want with a relay.  
However, if you want it to be off in the middle probably not.
In which case moving a switch with a servo will be the only way to solve the problem.

BTW.  What is analog R/C?
Even the el cheapo Futaba and Hi-Tec 2 stick radios are digital.  As in digital proportional.
Assume I want to reverse an electric motor with a DPDT switch using a "Car" type transmitter with a steering wheel.  Turn the wheel one way some distance, say past half way to a full Clockwise and the DPDT switch connects one way, return the steering wheel to center and the electrical switch centers to the OFF position; turn the wheel more than half way in the other direction and the DPDT switch connects the other way. Voltage and current requirements will be similar to what is required for an electric motor for motive power.

My interpretation of R/C is that they all appear to the user to be "analog", (although possibly an incremental analog if it is a pushbutton speed control,) AND the output, from the view point of the Receiver, is also an analog function, (although again, possibly an incremental value).  i.e.: a stick is moved a distance and the Receiver drives a device a distance porportional to the distance the stick is moved...or a button on the transmitter is pressed one or more times to produce an incremental change in the setting of the output device.  In trains this is like the throttle, either you push the stick forward to increase the speed or you press a button one or more times to set the speed to some value; and then you pull the stick back, or press another button multiple times, to slow down or stop.  It is "analog" as opposed to the digital "on/off".

There are transmitters that have simple toggle switches on them that cause a digital response on the receiver to turn something on or to turn it off, such as lights, a smoke unit, or horn, etc.

I already have the R/C transmitter and I don't want to have to buy another one to control other things,,, the one I have is a "car" controller and it can be set up to run up to 10 different cars (one at a time!) and only has three controls; Throttle, Steering wheel and an Auxilary knob that is also an analog control just like the throttle and steering wheel.  The rhetorical question is, why do I have to buy another transmitter when the one I have can remember the program settings for 10 different devices to be controlled?  I just want to do a "digital" control using the analog controller.

I have a couple of things I want to control that are already controled via a hand operated toggle switch that is a very STIFF switch and I think it would be hard on a servo to have to drive it.  I can replace the switch if I can find one that fits the space and will hand operate in a similar maner or I can get a bigger servo... or... maybe I can get a device that plugs into the receiver like a servo, but is actually a DPDT switch for reversing the polarity of an electrical current.

Likewise I want a solenoid that I can plug into the Servo output of the receive and control it, not as a variable position, but as a snap action (in/out) with the "analog" control on the transmitter.  I want to turn the aux knob on my controller and at a certain point the solenoid snaps to the other position and stays there until I turn the knob back toward the starting point... some hysterisis would be acceptable, i.e.: I have to turn it 3/4 turn CW to fire the solenoid and then turn it back about 1/2 turn CCW to pull the solenoid back, there should not be a point where the solenoid is rapidly reversing position.
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Rest assured a regular car type R/C controller is digital proportional.  It definitely is not analogue.

OK so you want no output when the stick is in the middle, and full voltage output in one direction or the other when the stick is moved one way or the other either side of rest in the middle?

That is really easy to do with an EVO # 2-M-F and two SPDT relays wired as a centre off DPDT equivalent.

I don't have any instructions on how to do it but rest assured it can be done.

In fact, because I have the separate parts to enable just such an operation I was contemplating making up a pcb that does just what you want.

The circuit wiring for a similar system using four relays to control 2 motors for a crane operation is shown on page # 9 of this pdf.     www.rcs-rc.com/PDF/RC_Modules/Instructions/RC_Modules.pdf
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If you want to stay fully solid state there is this nifty part called an H Bridge that does exactly what you want to do. It might require a few more electronics but it would remove all of the moving parts and they can be quite the current sources.

Tom Bray

How about 10 R/C relays?


A little clumsy with only 4 buttons to control 10 relays but it works well.

I hooked mine up to my computer and wrote a little basic code to operate my Mack.

Control functions on the left.

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You could also attach a small magnet to the servo and either let it rotate into the proximity of various reed switches clustered around the armature or in-line with armature movement.
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