How to power a relay

Discussion in 'General Electronics Chat' started by schifferer, Jan 24, 2016.

  1. schifferer

    Thread Starter New Member

    Jan 12, 2016
    Here is what I’m trying to do: have a push button where you push it and release, causing a motor to change direction (polarity).

    The motor is actually an actuator with built-in limit switches that shuts itself off until polarity is changed and it reverses until the other limit switch is hit, etc…
    The basics of the motor are it requires 12VDC with a 9 amp current at full load.
    Here’s more info if needed:

    I believe I have the right power supply for this: 12VDC / 10A.

    To switch the polarity I think I just need a DPDT switch or relay.
    I think 10A is too high for most switches so I’m guessing it needs to be a relay.

    To switch the relay I want a sturdy push on push off switch.
    Here is a switch that is rated for 2A / 250Vac. (I think I would just wire it as a SPST for the relay)

    Up to this point I think I have it figured out. Where I get confused is how to connect the switch to the relay’s coil.
    The relay’s coil is Ω so what needs to happen for it to activate?
    Can I run 12VDC/10A through the switch and coil or does there need to be a separate power supply for the switch and coil?
    Or can I use a resistor or something to make the 12VDC/10A usable for the switch and coil?

    I’m attaching a sketch of how I’m imagining this.
    Let me know if anyone has thoughts on a direction.

    Thanks a ton!

  2. MaxHeadRoom


    Jul 18, 2013
    You can also use a relay flip-flp circuit where each momentary push of the button reverses the motor.
  3. sailorjoe


    Jun 4, 2013
    Schaffer, the first thing I noticed is that you don't have an "off" switch in your second schematic.
    Second, you need to check the relay coil current rating. That will tell you how to activate it. If it's not listed on the relay, find the datasheet for it on line and you'll find it there.
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    A disadvantage of using a relay as shown is that for one direction of the actuator the relay coil will remain energised, consuming power. If this is a concern, a more complex circuit would be needed.
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
    An impulse relay is a standard electromechanical relay with extra parts that turns it into a toggle flipflop. With a momentary pulse to the relay coil, the contacts change state and latch there even after power is removed from the coil. So this type of relay doesn't have the standard normally open and normally closed contacts, because the contacts do not return to the same place every time the relay coil is off. Great for motor reversing applications.

  6. schifferer

    Thread Starter New Member

    Jan 12, 2016
  7. schifferer

    Thread Starter New Member

    Jan 12, 2016