433mhz transmitter controlled by 12v timer

Discussion in 'The Projects Forum' started by 007bigd, May 22, 2013.

  1. 007bigd

    Thread Starter New Member

    May 22, 2013
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    Hello... little unfamiliar with what I am trying to do, but I am hoping someone could help steer me in the right direction.

    Basically I have a remote start generator, the key fob of course transmits at 433mhz. I am looking for some sort of 12v timer actuated transmitter to replace the key fob, so the generator can start and then shut off at predetermined time.

    Ideally I need a 12 volt timer that can signal the transmitter an on time and an off time. Then The transmitter that will signal the generator reciever on and off.

    I realize there are 2 ways to do this, by hardwiring the timer into the receiver circuit OR providing a rf signal to do the job of the key fob which is the route I would like to take. The FCC ID# is YA3V750 on the back of the key fob if that helps at all.

    Does this sound at all feasible provided what ive mentioned? Thanks so much for the help and as a newbie, I appologize for my lack of understanding how to go about what I need. I have searched and searched and I come to you for help :D
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Why not just use a timer directly and forget the radio?
     
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  3. 007bigd

    Thread Starter New Member

    May 22, 2013
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    That really does seem to be the easiest and most direct route, I agree. But supplying the correct voltage to the correct circuit kind of worries me, when I dont what the controller operates on. I figure IF I can supply the frequency it needs to start and shut off and by doing so, would limit the level of tinkering with the controller and potential for me ruining it,lol. Im thinking in terms of less reconfiguring of the unit itself and more so configuring a timer actuated signal. But ideally if I knew the workings and/or how to test and measure the values of the receiver/controller that would be simpler.

    So unless I take this thing apart and figure the workings of the controller, id like to stick to modifying a transmitter via 12v timer.

    Im really open to constructive criticism of this idea, so if you think the timer actuated transmitter is not the ideal setup for a guy who really doesnt know how to get what he wants with what he gots, ill take any advice on a better way. This just seemed to be the least intrusive and manageable way I could think of for the project myself.
     
  4. wayneh

    Expert

    Sep 9, 2010
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    I certainly don't know anything about your generator but maybe if you post details about the make and model, someone here will know.

    Is there a manual start button on the generator? That might be an easy spot to "hack".

    Opening the transmitter key fob and hacking its button is another point of entry. Or hold the button down and control the power to the fob.

    Anyway there are lots of timers out there. Most I know of are like lamp timers but there must be a bunch of 12v DC timers as well. If you can find a timer that controls a 12V signal, you could use that signal to control power to the key fob or perhaps to act like the fob switch. There will likely be a 555 timer circuit (a one-shot, or monostable multivibrator) involved here to simulate holding the button down for a second and then releasing it, even though the timer may be holding its output steady at 0V or 12V.
     
    Last edited: May 22, 2013
  5. 007bigd

    Thread Starter New Member

    May 22, 2013
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    ... and get this, (I give you permission to chuckle)

    My initial option was to fabricate a fixture to hold the key fob and mount 2 12v solenoids to manually press the 2 buttons on and off. lol while Im sure I could get it to work, its just too crude and I know there is a better way.

    Again...if I had the confidence to open the controller and figure whats goin on inside with the reciever/controller to hardwire the timer, I would. But bottom line is I dont know circuitry well enough to do so and why im here asking some obscure method to use the remote. lol
     
  6. wayneh

    Expert

    Sep 9, 2010
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    Ha ha, yes the Rube Goldberg approach. I think we can eliminate moving parts easily enough. But I recommend a commercial solution for the timer itself. Lamp timers are digital, programmable, and just so darn cheap these days. No reason to build one.
     
  7. 007bigd

    Thread Starter New Member

    May 22, 2013
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    Yes, it does have a manual start... most important thing about the remote start is that it goes through a "start up procedure" where it actuates the automatic choke, starts the motor, auto-choke turns off, then applies current after motor is running, then it disconnects current before shutting off. Ill have to see about that process in manual mode. (just checked and it does not run through a start up or shut-down procedure)

    I ordered a new key fob so ill have one to dismantle without too much worry and will try that approach. Thanks alot...it helps to have another mind thinking and I think there may be a better way than where I was going.

    BTW this thing is a Model #46539 Champion 3500/4000 watt remote generator by Global power equipment... So far it works absolutley flawless and was 525.00 with shipping through amazon. Even has a 2 year manufacturers warranty of which I have spoke with Champion several times, so support has been swell.

    Thanks again, ill keep pluggin away at whats best. Your ideas were quite helpful. I think ill look into digging into the key fob and figure a switching method via timer perhaps. :)
     
  8. wayneh

    Expert

    Sep 9, 2010
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    I'll give a preview of my thinking. The pushbutton makes a connection between two conductors. One of them is likely either battery voltage or ground, and the switch turns on the transmitter for as long as you hold it down. Using a voltmeter, it should be easy to figure out which way the switching goes.

    A MOSFET controlled by a 12V DV timer signal on its gate pin can function as a very nice switch. Extremely high resistance when off, very low resistance when on, just like a button.

    The challenge is figuring out which conductor at the button is the battery +V line or which is the ground line. The MOSFET drain pin needs to be at a higher voltage than the source pin, so you need to establish the relative voltages at the button. You can avoid this challenge by just shorting the push button and controlling power to the transmitter from its battery. This way you know for sure which line you are switching.
     
  9. 007bigd

    Thread Starter New Member

    May 22, 2013
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    Thanks, ill look into it...So basically the MOSFET will act as a relay of sorts from what I gather. Ill see about 12v timers and ill get my new fob in a few days and research further in the mean time. I think thats a pretty simple approach utilizing my existing transmitter key fob.
     
  10. wayneh

    Expert

    Sep 9, 2010
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    Yup. They have the advantage of no moving parts and almost no power consumption on their own. But they have the disadvantage that the two circuits - the control signal and the power circuit - are not as isolated as they are by a relay. They literally share common ground. On the other hand, a relay can even switch AC power for instance, with no connection at all to the control, but you wouldn't do that with a MOSFET. There is also such a thing as a SSR (solid state relay) but it's not needed for your application.
     
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