PWM-Dimmed input to relay coil?

Discussion in 'The Projects Forum' started by benha, Mar 7, 2014.

  1. benha

    Thread Starter Active Member

    Jan 4, 2011

    I'm working on a controls project and could use a little help.

    What would be the word on using the load output from a PWM dimmer - I'm using an Abeltronics DIM11 - as an input to a relay coil? The attached drawing should help explain why I want to do this. Basically, the momentary button I’m using to control the DIM11 is a two-color illuminated Bulgin button that needs a DPDT relay to control the color. I need a signal to indicate the state of the load (on or off) to determine the color I should display, and by far the simplest way to do that is to use the load line as the input to the relay. I’m just not sure what effect the dimming would have on the coil.


    Thanks a ton.


    PS - Sorry about the crummy scan of the drawing.
    PPS - I note that I didn't draw the (-) side of the coil going to ground, but assume it does.
  2. wayneh


    Sep 9, 2010
    You need to integrate the signal, since the relay needs a steady DC current whereas the signal is pulsing. It's possible that a capacitor after a diode would provide enough smoothing to hold the relay activated while waiting for the next pulse. Can't tell without more detail (frequency, duty cycle, relay coil current). You also need to be sure that the DIM11 can output enough current to drive the relay. You may need to use another power supply to the relay, under control of the DIM11.