Adding 555 delay timer to an already existing Wireless transmitter

Discussion in 'The Projects Forum' started by 2electrified, Aug 12, 2013.

  1. 2electrified

    Thread Starter Member

    Sep 5, 2011
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    Here is what I am trying to do and need some help. Our local gun club wanted to have wireless transmitter and receiver setup on their clay target machines. Well, the gentlemen who did put it together put two transmitters in one box weatherproof handheld unit. One transmitter launches machine 1, the other transmitter launches machine 2. Now in order to get both machines to go off at once, they try to push both buttons to launch both machines at once, but because they are on the same frequency it does not work, so they have to press one button then the other immediately, but if they don't it throws the shooter off. So I am trying to see if its possible to add a simple monostable delay of 1 sec so when both buttons are pressed, the one remote button would have a delay without the person having to worry about pressing the buttons one after the other. I did successfully built a monostable time delay and it works on perfect. But now how do I add it to the already existing wireless transmitter circuit. I included a pic of one my 555 delay and a pic of the wireless transmitter circuitry layout hoping someone would be able to help me out. The final 555 delay circuit will be on soldered onto a much smaller pcb board. One the wireless transmitter, there are three buttons, I would like to use the top button, located the LED light. Thank you in advance for your help. Lisa
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,126
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    Does this mean they use some sort of encoded signal? I mean, why don't they both activate when either button is pushed, if they are on the same frequency?

    I'm just thinking there should be a more elegant solution, closer to what you want of a simultaneous triggering. Maybe transmit a 3rd signal encoded that either receiver accepts.
     
  3. sirch2

    Well-Known Member

    Jan 21, 2013
    1,008
    351
    So you want to press switch one and have switch two "pressed" one second later?

    What are the voltages across the switches?

    Does pressing a switch pull the signal low or high (i.e. is the voltage zero at all the switch contact when it is pressed)?
     
  4. 2electrified

    Thread Starter Member

    Sep 5, 2011
    30
    0
    @WayneH - it must be some sorted encoded signal. I am really not sure. All I know is there are two separate transmitters with the frequency of 315mhz mounted in one box and when both buttons are pressed nothing happens. But when each transmitter is pressed one at a time, the relays in the receivers go off. I really don't know how to add a 3rd encoded signal - do you?

    @sirch2 - the transmitters run off a 12v battery. The voltage across the buttons are 3.24 volts and when the button is pressed voltage drops to 0 volts.
     
  5. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Instead of modifying the transmitter, could you simply add a jumper wire between the relay coils so that both are energized whenever either receive a trigger signal? I'm making some gross assumptions like the relays have reverse voltage protection diodes on the coils, the circuit can safely provide double the current to the coils, both circuits share the same power and ground lines, etc.

    You could put it through a switch so that you can still control each independently if desired. If you could post some pictures of the top and bottom of the receiver circuit, we can offer some guidance if this sounds like an ideal solution.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    Do you always want both machines to go off at once? That would be easy to implement at the receiver end.

    BTW, I'm not poo-pooing your 555 idea. I'm just trying to avoid focusing on just one solution too early in the process.
     
  7. 2electrified

    Thread Starter Member

    Sep 5, 2011
    30
    0
    @wayneh - I don't think you're poo-pooing my idea. I greatly appreciate all the help I am getting. No both machines will not always be going off at the same time. They mix up it - they will shoot single clays from either machine, and then they shoot doubles from both machines. Each machine is 300ft from the shooter, and the machines sit 200ft across from one another out in the field.

    @elec mech - I don't have any receivers with me, I will be going to the club at the end of the week, at that time I will be able to take a pictures of the receiver itself and then I can post here.
     
  8. wayneh

    Expert

    Sep 9, 2010
    12,126
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    OK, well now with more details I think your 555 approach may be the way to go, at least for a quick fix. You can play with the delay time to make it as short as you can. My hunch is this will be quite small, but we'll see.

    From your measurements, it appears that the transmitter is triggered by grounding the switch. This same thing can be accomplished with an n-type MOSFET switch controlled by your timer. 2N7000 seems to be a commonly recommended MOSFET around here. You need at least about 10V on its gate to do its job (conduct), but you have this voltage available in your transmitter.

    The MOSFET will simulate pushing the button when a voltage is applied to its gate. Source pin goes to ground, and the drain pin will connect to the side of the button switch that has a voltage.

    The only part that's missing is how to make the 555 circuit produce a brief voltage on the gate of the MOSFET, some fraction of a second after the 555 receives the trigger pulse, the touch to ground provided by your 3rd button.
     
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