PWM with 555 timer help

Discussion in 'General Electronics Chat' started by 386DX40, Jun 18, 2014.

  1. 386DX40

    Thread Starter New Member

    Jun 17, 2014
    Hello all,
    Just joined the site and making my first post.
    Worked in Electronics many years ago so basically familiar with it but my knowledge has deteriorated due to old age!!

    I'm here on an offshore drilling vessel off the coast of South Africa.
    One of our treadmills crapped out. When the treadmill is activated it goes bonkers. I've tested motor and went through all of the connections. I've tested the current draw and didn't see anything that would cause it to shut down. No current spikes, no voltage drops. The controller is running off a small Microchip controller of some sort.
    Anyway. I'm wanting to rig up a manual control for the treadmill to get us through until a replacement arrives.
    Ive got limited access to electronic parts but I do have enough parts to make the 555 pwm circuit listed HERE.
    I've built that circuit many times and used it for many different things but never to drive a motor rated at 160v.
    How would you interface this circuit to a 160v DC circuit?
    I've got a couple MJ11021 & MJ11022 that would work I think but don't want to burn up all my parts experimenting!!
    One idea I had was to use some type of buffer circuit to connect Pin 3 to the Darlingtons.

    Any help??


  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    The circuit you displayed will work with the transistors that you have, they are rated at 250V min, try it dimming a bulb at first,if all ok try it on the motor.
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    ....not forgetting a freewheel diode to protect the transistors from back-emf spikes.
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Well the driver portion may work with the 160V (I did not personally check that) but one thing you'll need is a voltage regulator to get the 555 not to explode on power on.

    Kinda obvious, but I'd rather say it up front before you put your eye out. :p