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Thread: Staging assist PWM output? SSR? Is there a better way to control the T/B solenoid?

  1. #1

    Default Staging assist PWM output? SSR? Is there a better way to control the T/B solenoid?

    This was brought up regarding PWM control of some Water/Meth solenoids, which has me wondering about my SSR ability to accurately control my TransBrake solenoid during "bump":
    Quote Originally Posted by rdkerne View Post
    An SSR is not a device that transfers pulse width modulation signals well, which is why Holley recommends the proper driver/transistor device. Most of the time, the time it takes for the SSRs internal LED to turn off is the limiting factor for switching frequency. Also, a DC circuit is not as good as an AC circuit as the current in an AC circuit drops to zero between cycles which is used to turn on and turn off the power circuit in an SSR (known as zero crossing). A DC circuit does not modulate so the relay has no "zero crossing" to respond to. The heat you feel is related to the amp draw of the solenoids, not a result of PWM operation.
    During the "bump", the "off" time that is being commanded of the SSR controlling my Transbrake solenoid is obviously very small amount of time. My question: Are some SSRs quicker acting than others? And able to control bump/creep better than others?
    Is my 4 pole Fotek SSR harming my ability to get my combo to smoothly bump into the beams?
    Link to exact SSR I'm using, specs say 1 millisecond <on+off> switching time:
    Last edited by 3pedals; 07-22-2019 at 07:06 AM.

  2. #2


    That brand did not work for me at all. I went with a Crydom and it's perfect.

  3. #3


    The Amazon Fotek SSRs are known to be knockoffs. Most are using the NOS nitrous relay for Transbrake use. Crydom D1D40 works as well.
    Any quality SSR should work fine for Transbrake or Water/Meth use, as long as it's within specs. I don't think you'll find an advantage with one specific brand.
    Last edited by allan5oh; 07-24-2019 at 11:21 PM.

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