DC motor forward and reverse

Thread Starter

91five0

Joined Jan 19, 2021
24
if I want a three position on-off-on switch, with both sides being straight polarity, do I need a DPDT or can I do it with a SPDT
 

djsfantasi

Joined Apr 11, 2010
9,185
if I want a three position on-off-on switch, with both sides being straight polarity, do I need a DPDT or can I do it with a SPDT
You need a DPDT to reverse the motor.

There is a way to use a SPDT, but it’s more complicated. Using a DPDT is the easiest and most straightforward.

(To use a SPDT, you need TWO independent power supplies. Then, you have to wire them up in a special way to the switch. Not worth the extra expense and engineering)
 

MisterBill2

Joined Jan 23, 2018
19,072
I think that I saw, close to the start of this thread, a comment that the speed range would be zero to TEN RPM. Having a stable speed that slow would be a challenge for most DC motors. So a reduction gearing arrangement may be useful.
And the circuit shown in post #20 will allow the use of single pole switches that do not have a center off position. So that may offer some benefit. It is about the same as I recently suggested for another thread.
 

MaxHeadRoom

Joined Jul 18, 2013
28,780
And the circuit shown in post #20 will allow the use of single pole switches that do not have a center off position. So that may offer some benefit. It is about the same as I recently suggested for another thread.
KB Co. One of the largest manufacturer of DC/BLDC motor control boards, offer a special switch for the reversing operation, and they also use it in their complete controller units.
It consists of a DPDT switch with centre off, but also a built in prevention of switching directly from one dir to the other dir by including a forced physical stop at centre until the toggle is relaxed.
The DPDT ones with centre off I showed a link to are only just over $5.00 ea..
Max.
 
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