Simple (?) Automatic Polarity Reversal Circuit For Dual DC Motor Control

Thread Starter

Toby-Won

Joined Feb 3, 2016
4
Looking for input from someone a bit more technical than me...

I am working on a project that is runs two DC motors from only one switch. The issue is that regardless of the polarity directed into motor #1, motor #2 can only accept one polarity direction (please refer to my attached file).

I have searched for several weeks, but am having no luck. Most likely my inexperience in electrical systems is not taking me in the right direction.

Any help regarding this would be appreciated.

A few details...
Power Supply: 12 VDC
Motor #1: 12 VDC / 10A, bi-directional rotation
Motor #2: 12 VDC / 5A, unidirectional rotation only
Switch: Reversible - DPDT

Thank you in advance for your feedback.
 

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wayneh

Joined Sep 9, 2010
16,275
That's a good simple solution, but unfortunately wastes about 10% of the power used by M2. A complex circuit, and active rectifier, could eliminate that loss but is likely not warranted.
 

MaxHeadRoom

Joined Jul 18, 2013
20,059
So you would put the wires from the switch on the AC inputs of the bridge rectifier?
Yes it is done quite frequently to ensure correct polarity.
The other simple way but more parts is two DC D.P. relays with a series connected diode to each coil, each one reversed biased to the other.
Max.
 
i think simply u can but two diodes on the two terminals of M2 as follow
the 1st diode the cathode is connected to the +ve terminal of M2,and the other the anode is connected to the -ve terminal of M2
 

Thread Starter

Toby-Won

Joined Feb 3, 2016
4
Thanks for the information.

I did some research regarding the bridge rectifier and feel that this may be the simplest solution for this project. Fortunately, the input to M2 can be reduced by up to 15% without any adverse issues, so the losses mentioned above should be manageable.

I have a few different rectifiers on order and will try them out tomorrow.

Again, thank you for setting me it the right direction - I appreciate the responses.
 

k7elp60

Joined Nov 4, 2008
561
Thanks for the information.

I did some research regarding the bridge rectifier and feel that this may be the simplest solution for this project. Fortunately, the input to M2 can be reduced by up to 15% without any adverse issues, so the losses mentioned above should be manageable.

I have a few different rectifiers on order and will try them out tomorrow.

Again, thank you for setting me it the right direction - I appreciate the responses.
Her is a complete schematic for you, Just make the sure the diode rating for the bridge rectifier is = to or greater than the motor current under loadMOTORCONTROL.jpg
 

crutschow

Joined Mar 14, 2008
24,404
To reduce the voltage drop, you could use some large (≥ 10A) Schottky type rectifiers.

You could also use a 3PDT center-off switch with the 3rd pole controlling M2.
Connect the 3rd wiper to V+ and both throws in parallel to M2's plus terminal.
Connect M2's minus terminal to V-.
 
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