Toggle to momentary?

Discussion in 'General Electronics Chat' started by rjjenkins, May 24, 2012.

  1. rjjenkins

    Thread Starter Active Member

    Apr 16, 2011

    I am making some simple RC projects using these cheap Chinese remote control units like these

    They work fine, but the outputs toggle and I need them to be momentary. They use the chip SC2272-T4 as the decoder and as far as I can see there is no option to convert it to momentary mode. (The SC2272-M4 seems to do this but I'm reluctant to try to unsolder/replace one chip with another).

    Any ideas? I can't think of any way to make a toggle output into a momentary one:

    (The advantage of using these units is that they are cheap and come with a ready made keyfob transmitter: everything else I can find seems to be quite a bit more expensive and would need me to provide a transmitter housing/power supply/switches etc.)
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    You either have to change the chip to a momentary one (the M-suffix) or modify your transmitter. The transmitter button signal could be driven by a low frequency rectangular wave WHILE the button is being pressed. This would continuously toogle the receiver output.

    At the receiver output there needs to be a monostable timer which is constantly being retriggered by the received signal (which happens to be the same signal you drive the transmitter with). As long as you press the button the monostable output will be ON.

    Looks easier to change the chip :)
  3. rjjenkins

    Thread Starter Active Member

    Apr 16, 2011
    Yes - thanks. I think I've now found a module with the other chip