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Minimum number of relays per h-bridge

  1. Mar 3, 2010 #1
    Hi experts,
    Is it possible to form a h-bridge using 2 spdt relays?
    What i can find on the net are h-bridges using 4 spst relays or using other types of relays.

  2. jcsd
  3. Mar 3, 2010 #2
    What do you think? Would it be possible to construct and H bridge with 1 DPDT relay?
  4. Mar 3, 2010 #3
    Yes. You need to choose between "make before break" (Form D) or "break before make" (Form C) contacts.

    Bob S
  5. Mar 3, 2010 #4
    i think it is possible and connected one to test but the motor did not operate bi-directionally according to plan. That is why i wanted to confirm this.
  6. Mar 3, 2010 #5
    Thanks Bob S!o:)
  7. Mar 3, 2010 #6
    On certain motors, like fractional HP induction motors (capacitor start, split phase, repulsion start), there is a starting coil and a running coil. If you try to reverse the motor at full speed, it won't. It has to slow down until the centrifugal switch engages, and preferably until it stops before you reverse it.

    Bob S
  8. Mar 4, 2010 #7


    User Avatar
    Science Advisor

    Yes, see the last entry in this thread:

    You would just connect the two coils of the relays in parallel or in series and switch them at the same time.
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