How to auto forward and reverse DC motor

Thread Starter

Don_Fila

Joined Nov 26, 2021
158
How to control DC motor forward and backward automatically without using a manual push button, please can you help me with circuitry. Your help will be highly appreciated .
 

MaxHeadRoom

Joined Jul 18, 2013
25,623
What kind of mechanism is it for?
One device that does this without reversing the motor, is an automotive wiper motor and mechanism.
There are other similar mechanical ways.
 

Thread Starter

Don_Fila

Joined Nov 26, 2021
158
What kind of mechanism is it for?
One device that does this without reversing the motor, is an automotive wiper motor and mechanism.
There are other similar mechanical ways.
The motor is a dvd brushless motor or brushless motor I'm using it in a device that I built to dry wet PCB so I want it in a such way that if I place the PCB on the metal surface the motor should be able to move forward and reverse until I stop. What I want now is a circuit that can auto reverse and forward the motor
 

LesJones

Joined Jan 8, 2017
3,773
If the motor can be reversed by reversing the polarity of the supply then you could do what you want using a three pole double throw relay. (Or a DPDT relay plus a a SPST or SPDT relay.) One set of contacts would be used to latch the relay in. One end of the travel you would have a set of contacts that closed. This set of contacts would pulse the relay closed and it would latch in using an NO contact on the relay. The other end of the travel a set of contact that were normally closed. these would be connected in series with the relay coil causing it to drop out at that point. The remaining two sets of changeover contacts would be wired to reverse the motor. (If you used two relays you would connect the coils in parallel. One relay (The single pole one would do the latching.) and the DPDT one would do the reversing.

Les.
 

MaxHeadRoom

Joined Jul 18, 2013
25,623
Have you explored all the options for doing it mechanically and maintain one motor direction?
It sounds like an application that could be open to it?
It can often be troublesome, when you reverse a motor constantly with no pause in between.
If it is a brushless motor, I assume it has a PWM drive if some kind?
 

MisterBill2

Joined Jan 23, 2018
12,678
I am guessing that the TS also wants to use a portion of the DVD player hardware in the project. If that is the tray IN/OUT mechanism I doubt that there is enough force available for any serious wiping of a wet PCB. Those players usually have switches to stop the motor at each end of the motion, and so the scheme suggested by LJ in post #4 should work very well.
 

Thread Starter

Don_Fila

Joined Nov 26, 2021
158
Have you explored all the options for doing it mechanically and maintain one motor direction?
It sounds like an application that could be open to it?
It can often be troublesome, when you reverse a motor constantly with no pause in between.
If it is a brushless motor, I assume it has a PWM drive if some kind?
Yes, I have used relays to work it out manually and it's ok. Does it mean reversing motor constantly will affect the life of the motor?
 

MisterBill2

Joined Jan 23, 2018
12,678
I have never seen a brushless motor in a consumer grade DVD or CD player. And if the motor reverses with just swapping polarity at the motor I doubt that it is brushless. Have you tried running the motor in both directions just by reversing the power connections?? What voltage does the motor run on?? If it is a BLDC motor the driver may have a reverse control line. What function in the DVD player did the motor have? Load/unload, tray IN/Out? disc rotate? or laser move ? three different functions, three different motors.
 

Thread Starter

Don_Fila

Joined Nov 26, 2021
158
I have never seen a brushless motor in a consumer grade DVD or CD player. And if the motor reverses with just swapping the polarity of the motor I doubt that it is brushless. Have you tried running the motor in both directions just by reversing the power connections?? What voltage does the motor run on?? If it is a BLDC motor the driver may have a reverse control line. What function in the DVD player did the motor have? Load/unload, tray IN/Out? disc rotate? or laser move ? three different functions, three different motors.
When I swap the polarity it move forward and reverse. Yes, it is tray in and out and also the laser moves.
 

LesJones

Joined Jan 8, 2017
3,773
This should work.
250722.jpgThis is using a three pole double throw relay. To use a DPDT relay and a single pole relay just parallel the coils. use the single pole relay to do the latching.
NO stands for normally open contact.
NC stands for normally closed contact.
If it moves and does not reverse just reverse the connections to the motor.

Les.
 

MisterBill2

Joined Jan 23, 2018
12,678
The circuit in post #15 will work very well, BUT it may be that the relay voltage and the motor voltages are not the same. In that case the motor voltage should only be connected to the relay contacts feeding the motor, and the relay coil supply can be connected as the supply connection shown on the drawing.
To stop the motor motion the motor supply must be switched off.
This control scheme does not include a stop mode.
 

Thread Starter

Don_Fila

Joined Nov 26, 2021
158
The circuit in post #15 will work very well, BUT it may be that the relay voltage and the motor voltages are not the same. In that case the motor voltage should only be connected to the relay contacts feeding the motor, and the relay coil supply can be connected as the supply connection shown on the drawing.
To stop the motor motion the motor supply must be switched off.
This control scheme does not include a stop mode.
So far this what I designed and its working fine. The motor auto forward and reverse depending on the RC network to operate forwarding and reversing . Please can you go 20220726_181631.jpgthrough if there is no mistake in my circuit.
 

LesJones

Joined Jan 8, 2017
3,773
Hi sghioto, The way the motor is connected to the relay contact requires both relays to be energised for one direction of the motor and both relays to be de-energised for the other direction. So his circuit is correct for driving the motor backwards and forwards. But the circuit has no means of controlling the positions when the motor reverses.
A third version of the design in post #15 could be made using three single pole double throw relays. That design controls the points where the direction changed by the position of the limit switches.
The circuit in post #17 could be modified by replacing the 555 and the timing components with another relay wired in the same way as the left hand set of changeover contacts in post #15.

Les.
 

Thread Starter

Don_Fila

Joined Nov 26, 2021
158
From your drawing both relays are activated when the output from the 555 is high.
The drawing below shows the corrections circled in red.
View attachment 272281
Hi sghioto, The way the motor is connected to the relay contact requires both relays to be energised for one direction of the motor and both relays to be de-energised for the other direction. So his circuit is correct for driving the motor backwards and forwards. But the circuit has no means of controlling the positions when the motor reverses.
A third version of the design in post #15 could be made using three single pole double throw relays. That design controls the points where the direction changed by the position of the limit switches.
The circuit in post #17 could be modified by replacing the 555 and the timing components with another relay wired in the same way as the left hand set of changeover contacts in post #15.

Les.

Please can you support it with a diagram. I mean the modification of post #17 which it is referred to post #15
 
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