I need an electronic device (circuit) that will act as a DPDT switch to run a 20ma 12vdc motor forward and reverse. The trigger to activate is a + 2vdc pulse to activate the motor in one direction and when signal is removed the motor runs the other direction. I do not want to use a standard DPDT mechanical switch or relay. Can anyone help me please.

Thank you, Ron

 

The circuit you need is called an H-bridge.
You can buy it ready made as L298N motor driver.

 

A SPDT center off toggle switch can control a motor driver like this one. The toggle switch is only switching a few mA, the module controls power to the motor.

 

Any H-bridge MOSFET will fulfill your purpose. You can choose from L293D, L298N, IBT-4 etc. depending on the specifications of your motor.

 

As an aside, that L297N board is sold by quite a few vendors where it always claims good for steppers, but the unit fails to include the neccesary current control ability needed for a stepper.
So good for DC motor only. !

Note: the L298N IC itself does however have the feature, just not facilitated on these boards.

 

The trigger to activate is a + 2vdc pulse to activate the motor in one direction and when signal is removed the motor runs the other direction.

Don't you also want an 'off' function?

 

While the old L298 is an H Bridge, consider the voltage drop (loss) using it. There are much better H Bridge modules available using MOSFETs. Google is your friend.

Ron

 

Don't you also want an 'off' function?

No I do not need a off position, the circuit need to be on all of the time and when triggered it reverses the motor.
Thank you, Ron

 

Are you going to reverse it instantaneously?
Then you must include some sort of SOA limiting.

 

How frequently does the 2V pulse occur, and what is its duration?

 

How frequently does the 2V pulse occur, and what is its duration?

Thank you for your reply. The +2 volt signal is on for approximately 3 to 5 seconds turning the motor one direction. Then when it stops it reverses the motor for .5 seconds then off. When it is off it’s turned back on by the 2volt signal in the first direction for 3 to 5 seconds then stop and trigger the motor the other direction for .5 seconds and so on.

Thank you, Ron

 

No I do not need a off position, the circuit need to be on all of the time and when triggered it reverses the motor.
Thank you, Ron

Thank you for your reply. The motor is run in one direction for about 3 to 5 seconds and when the 2 volt signal stops it triggers the .5 second timer to trigger it in the other direction. I guess any time delay between forward and revese is the motor being shut off and then triggered to the other direction?

Thank you, Ron

 

Any H-bridge MOSFET will fulfill your purpose. You can choose from L293D, L298N, IBT-4 etc. depending on the specifications of your motor.

Thank you for your reply and thank you so much for answer and I do think this is the way to go. I have ordered some and will start playing with it and making my trigger for the reverse function.

Thank you, Ron

 

Any H-bridge MOSFET will fulfill your purpose. You can choose from L293D, L298N, IBT-4 etc. depending on the specifications of your motor.

Thank you for your suggestion and it looks like I will try it out

thank you, Ron

 

While the old L298 is an H Bridge, consider the voltage drop (loss) using it. There are much better H Bridge modules available using MOSFETs. Google is your friend.

Ron

Thank you for that suggestion and I’m looking at the MOSFET H bridge circuits that I can use and adapt.

Thank you, Ron

 

As an aside, that L297N board is sold by quite a few vendors where it always claims good for steppers, but the unit fails to include the neccesary current control ability needed for a stepper.
So good for DC motor only. !

Note: the L298N IC itself does however have the feature, just not facilitated on these boards.

Thank you for your great information and I’m looking in to them

Thank you, Ron

 

I want to thank everybody who replied and I appreciate it very much. The motor I’m controlling is a very small 12vdc gear motor. I have tested this motor and it draws no more than 20ma when bogging the motor with load and runs continuously at 16ma. So I’m well under 1 amp and don’t need big power rated devices. Any leads to circuits to build this would be greatly appreciated

Thank you, Ron

 

As Reloadron ponts out there are down sides to the L298N board, but in your case where the currents are rather trivial it may be a quick and easy way to go.