Possible to replace POT with On/Off switch?

Discussion in 'General Electronics Chat' started by dirtyrice, May 6, 2009.

  1. dirtyrice

    Thread Starter New Member

    Apr 29, 2009
    6
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    I am new here and found this site looking for a few answers. First off, I can't get into the project I am working on as of yet, but I will have more info shortly.

    My question right now is this...I am using a DSM radio transmitter and receiver (from RC car), but I want to change the steering control or pot to a on/off micro switch. Is this possible and still allow the receiver to function? The steering channel on the receiver is going to be running a "battleswitch" from Dimension Engineering.

    Basically, all I need is for the channel to operate the relay in the battleswitch, but I need it to do it via radio control. Will the on/off act the same as the pot, just not variable output?

    Thank you in advance...BTW, I think I'm going to like it here....
     
  2. dirtyrice

    Thread Starter New Member

    Apr 29, 2009
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    Bump! I need help with this guys....

    I know you can replace the pot with a switch, but what do I do with the third wire? The switch needs two and the pot has three.

    I am a total noob on this stuff and need help. Sorry for my massive amount of ignorance on the subject.

    Will the switch still allow the receiver to function as usual?
     
  3. Butterworth

    Active Member

    May 6, 2009
    135
    3
    Hello,

    I am not entirely sure about this answer as I am still learning myself, but a "pot" is a variable resistor and the purpose between the pot and on/off switch are different. My guess would be no, it will not act the same if you take out the pot and replace it with a switch. You may however, put the switch inline with the pot to cut the current but still have the pot functional.
     
  4. dirtyrice

    Thread Starter New Member

    Apr 29, 2009
    6
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    Thank you for the response. Basically, what I need (after radio transmission) is for the output on the steering channel of the receiver to be 4.8-6V at all times when the switch is activated. As it is now, the voltage varies due to the pot.

    Thank you again for the quick response.
     
  5. DonQ

    Active Member

    May 6, 2009
    320
    11
    There are things you could do to replace the pot with a switch, but the output on the receiver would still be a PWM signal designed to operate an RC servo or some other PWM decoder device.

    Since what you seem to be saying is that you want to operate a switch on the receiver end, I would suggest this. Since you don't know what to do to replace the pot with a switch (and some resistors), you probably wouldn't be able to decode the PWM signal on the receiver. There are circuits you could buy to do this, but it may just be easier to use a regular RC servo to operate a mechanical switch at the receiver end. Then, when you turn the pot one way, the servo moves away from the switch. When you turn it the other way, it activates the switch. You could even put a cam on the servo and have it operate a number of switches depending on how far you turn the pot.

    This is probably the easiest way, and lots of devices do this. Past that, you need either to program a PIC, or buy one already done.
     
  6. dirtyrice

    Thread Starter New Member

    Apr 29, 2009
    6
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    Actually, what I need is the pot on the transmitter side to be either on or off. The receiver end is going to have a relay to operate a soleniod.

    I guess what I am asking is if the pot can either be used for only on/off operation or whether I can put a switch in its place to become either on/off.

    Sorry for the confusion. I am new to this and without 'showing' someone what I want to do, it is hard for me to explain.

    Thanks for the response!
     
  7. Von

    Active Member

    Oct 29, 2008
    65
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    Rather than modify the Tx... there are dry contact "modules" available for use in place of a servo.

    http://www.dimensionengineering.com/PicoSwitch.htm

    If you need more current capability you can add and additional (interposing) relay.

    This will require a separate power source for the solenoid, etc.
     
    Last edited: May 6, 2009
  8. DonQ

    Active Member

    May 6, 2009
    320
    11
    No matter what you do on the transmitter end, you will not be able to get a 0V/5V state change on the output from the receiver. Switches, pots, magic fairy dust... nothing on the transmitter will give you the output you want directly from the receiver.

    The output from the receiver is a pulse, varying from about 1 to about 2 milliseconds long, in (usually) about a 20 millisecond frame. It has been that way for quite some time, it is that way now, and it will be that way far into the future.

    A "module", like the ones suggested above, can change the output from the receiver and give you the sort of signal you want. If that's the way you want to go, I would suggest that you first get it working with the pot, then you can deal with replacing the pot with a switch later.

    If your main goal is just to replace the pot with a switch, knock yourself out! I hope you can find someone who will explain it to you. But I thought you wanted to get a 0 to 5V state change at the receiver end. Replacing the pot with a switch is not what it takes to do that.

    A working solution, one that is easy to explain, and easy to implement, is the one I already described.
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Dirtyrice, what are the current maximum and minimum voltages out of the receiving unit with the transmitter's pot turned to the two extremes?
     
  10. dirtyrice

    Thread Starter New Member

    Apr 29, 2009
    6
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    Believe me when I say this...I truly appreciate your response and very logical input on my delemma. Unfortunately, I find your post a little on the rude side as well as self centered. Once again I do appreciate the help, but the suggestion you gave me (using a servo to operate a switch) is not what I need for my project.

    You are right, the receiver operates on a pulse system and this is why I came here....looking for as many options as possible, if any, to get a straight 5V out of the receiver (which it has already, but I need it switched, not variable or pulse).

    You sound like you know what you are talking about and I am not disregarding your input by any means.

    I am not trying to start a war or anything like that, but please understand I am new to this and your way or the highway doesn't sit well with me, especially since it isn't going to work for my application. Maybe my local electronics supply store has some of this "magic fairy dust" you referred to?

    Once again, thank you ALL for the input and please keep them coming if you know something.

    Von, I am going to be running the dimension engineering 'battleswitch', which is the same as the 'pico', just handles more amps.
     
  11. dirtyrice

    Thread Starter New Member

    Apr 29, 2009
    6
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    next question....Will the pot operate the pico/battleswitch as if it were an on/off switch? This is all I need it to do is turn the relay or pico switch on and off, but instantly, not at full turn.
     
  12. Von

    Active Member

    Oct 29, 2008
    65
    0
    A switch (or relay) such as we are specifically talking about here has only two states, on or off. That is all it can do. So yes it will work as you want, an on/off switch, instantly (as soon as you push the stick).

    The switching will occur when you move the stick to the full end position, the same as a toggle switch on the Tx.
     
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