2 differents voltage level in 1 complete duty cycle of PWM

Discussion in 'The Projects Forum' started by zulkifli, Jun 16, 2009.

  1. zulkifli

    Thread Starter New Member

    May 5, 2008
    Dear All,

    im trying to design a system whereby to open a valve using PWM. The only problem with this system is that, it require 2 different voltage levels with the same amount of duty cycle of the PWM. Here i attach as in the diagram below; The valve require 12v to open and remain to open it require just 3v. Can anyone please advise on how can i implement this. i know quite well on how to implement PWM either programmable or analog device but not with 2 voltage in single duty cycle. Please let me know if this is possible. thanks :confused:

  2. SgtWookie


    Jul 17, 2007
    What's your supply voltage?

    I think you're really making this more complicated than you need to.

    If your supply is 12v, you simply need to provide 100% duty cycle until the valve opens; then around 25%-35% duty cycle to keep the valve open. Use a flywheel diode across the valve's solenoid to provide a current path for when the PWM supply is off.