Author Topic: Flyback diode for reversing 12V 3A DC motor  (Read 1389 times)

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Offline SlowBroTopic starter

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Flyback diode for reversing 12V 3A DC motor
« on: September 25, 2019, 03:29:44 am »
What specs ought I be looking for, for a flyback diode on a 12V 3A DC linear actuator? (I don't know the RPM.) It's reversed using a pair of SPDT relays. I'm thinking a bidirectional zener but no clue how many volts/current/etc. I'm aiming to protect the relay points.
« Last Edit: September 25, 2019, 03:31:42 am by SlowBro »
 

Offline Zero999

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Re: Flyback diode for reversing 12V 3A DC motor
« Reply #1 on: September 25, 2019, 08:03:32 am »
If you have access to the 12V supply, then a bridge rectifier will do. Connect the negative to +12V, the positive to 0V and the AC part across the actuator.

Failing that, two 18V zener diodes connected back-to-back, in parallel with the actuator, will do. They don't have to dissipate the full power continuously so something like 3W will probably do.
 
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Offline T3sl4co1l

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Re: Flyback diode for reversing 12V 3A DC motor
« Reply #2 on: September 25, 2019, 08:07:54 am »
Or a bidirectional TVS, like a P6KE18CA or SMAJ18CA.

Don't forget the DC input side of the relay needs to be well bypassed also; if it's supplied by long wires, you will get some flyback from that direction as well.  A local TVS or capacitor there may be desirable then.

Tim
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