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Best RC snubber

Discussion in 'Electronic Basics' started by Peter Kiproff, Jan 4, 2005.

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  1. I have a hydraulic valve on a break press, 115V approx 1A+ that when opened
    produces a nasty spike!

    This affects other logic, I tried 47 ohm 1/2 W in series with .1 uf @ 600V.
    across the coil.
    This is in a remote local.

    What would be your best guess to tame this? without scopeing it

    should it be across the coil or across the switch or relay?

    Thank you for helping.

  2. The wiring to the coil may be as much of the problem as the coil,
    itself, since it may be acting as the antenna.

    I would want to wire the coil with a pair of wires that came back,
    together, to the contact that drives it, and put the snubber device
    across that pair, right at the contact. This will slow the rate of
    rise of voltage all the way to the coil, including the wires.

    Your snubber values are reasonable, but you might want to lower the
    resistance a bit. Say, 22 ohms. This will still limit the worst case
    turn on current spike to about 5 amperes which should do little damage
    to most relay contacts. You might also want to parallel the capacitor
    with an MOV rated for 120 volt AC service, to make sure the inductive
    pulse does not force the voltage above the capacitors rating.
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