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
    4
    0
    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:

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  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    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.
     
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