Motor Control?

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I am just trying to power a motor through a relay. I need to pins though to reverse the polarity to get forward and reverse. Does anybody know how to hook up relays or transisters so that when one pin is on and the other is off the motor goes clockwise and when I flip the pins states the motor turn counter clockwise.

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If this is a simple DC motor then the easiest thing would be to have an On/Off relay (single pole ok or even a power transistor or FET) and a direction relay (2 changeovers). Put diodes across the coils to kill back EMF. The relay(s) should be driven with open collector transistors.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I figured out how to wire a double pole double throw switch to reverse a motor (way back when) by drawing a picture of the switch and motor and battery in fwd and back hookups, look and see what connections stayed the same and what moved. Turns out its simple... there is a wire from pole 1 position 1 to pole 2 position 2, and from pole 2 pos 1 to pole 1 pos 2. They 'cross over'. They sell relays wired like this called 'reversing relays' oddly enough.

Imagecraft compiler user

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Google "H bridge relay".
4 spst is the easiest to visualize.

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You will need to use a relay with 2 contacts.

If you have a part number for the relay you are using i can tell you the terminal numbers you need to use.

Say your using an omron relay that has the following pinout:

   1                2
   =---+            =---+
       |                |
   3   |            4   |
+--=   |         +--=   |
|      |         |      |
+-|  |-+         +-|  |-+
    /                /
    |                |
    o                o
    5                6

o-------[coil]-------o
7                    8
Forward/Reverse Circuit:

Positive
-----| |-----+-------------(motor terminal 1)
    5   3    |
             |
-----|/|-----+
    6   2
Negative


Negative
-----| |-----+-------------(motor terminal 2)
    6   4    |
             |
-----|/|-----+
    5   1
Positive

Index:
-| |-  = Normally Open Contact
-|/|- = Normally Closed Contact

When you have power across the coil (7+8 in my example) you will run the motor in one direction and when you don't have power you will run in the other direction.

You will need a way to cut the positive power to start and stop your motor. So you will have to use a 2nd power relay or a switch with memory. If you have an extra relay, a normally open push button and a normally closed push button you can make a simple motor start circuit:


   Normally Open   Normally Closed     Relay Coil
    Push Button      Push Button        
     (start)          (stop)
(+) -+---| |---+-------|/|---------------( )--- (-)
     |         |
     +---| |---+
    Normally Open
    Relay Contact

Then you can just use the other relay normally open contact to cut the positive line before your forward/reverse circuit.

I'm not a cartoon character but I play one in real life.