The following post discusses the wiring connections for driving a DC motor in clockwise and anticlockwise directions with the help of a single toggle switch and a relay circuit. The idea was requested by one the interested followers of this blog. Let's learn more:
Technical Specifications
Hi,
please help.
We have our project in school.
Our professor asks us to design a transistor together with a relay that allows a motor to rotate clockwise and then , a switch will be press , then will rotate counter-clockwise.
Thanks in advance.
The Circuit Design
A DC motor can be very simply rotated both ways in clockwise as well as in anticlockwise directions by flipping the supply inputs to it.
However the above reversing requires flipping of both of its wire polarity with the connected supply.
Therefore it cannot be done by using a single relay or switch.
However by using a couple of relays, a single switch operation becomes feasible for toggling the connected DC motor in both directions.
The following circuit shows the wiring details of the relay with the motor which is controlled by a transistor driver stage.
On switching power ON, the motor starts rotating in either clockwise or anticlockwise direction depending upon the wire polarity of the motor.
When SW1 is pressed, the direction gets instantly reversed and continues until S1 is switched OFF.
Actually the transistor stage is not required here, the implementation could be done simply with the relays and SW1.
More simply, the whole operation can be conducted using ordinary DPDT toggle switches.
Anonymous says
Best one for college robo compition
Anonymous says
Is it applicable to use 12V DC relay? and a 5v dc motor?
Swagatam says
Yes it can be applied, but the 12V positives from the relay contacts should be disconnected and connected to a +5V supply.
Anonymous says
Hello, can you explain how the circuit works? Thanks.
Swagatam says
the relay contacts are wired such that the motor receives (+) and (-) supplies across its terminals, the above polarity simply reverts when the relay is activated by pressing SW1, and vice versa.
Anonymous says
Hello Swagatam,
I really like your projects and ideas. I have one question about above circuit. I have same the DC motor driver circuit except two separate switches for fwd/ rev. The issue is when i run the motor, the relay's strip contact will shot. I think it is because of "back emf" or high current. Please advise what is the cause and how to resolve that.
Thank you
Swagatam says
It's not because of back emf, back emf won't damage relay contacts…it's probably due wrongly rated relay contacts….your motor is consuming more current than the maximum relay contact specs.
using powerful relays is the only solution.
Anonymous says
Got it. Thanks you!
Rabiu says
A good one for my curtain control.Thanks!
Anonymous says
Hi, I'm the one who asks this and I forgot to say thank you. It really helps. Thank you. I wish you'd continue helping others. God bless.
Swagatam says
You are welcome!
Vaibhav Dixit says
Can It be done By using Only One Switch like a remote in Chinese Toys. Please Explain?
Swagatam says
yes by using a DPDT switch, and wiring its contacts in a similar fashion to the shown relay contacts
Jordy Brusselman says
Hello i'm a real noob when it comes to electronics :p Can this motor go counterclockwise to iff I use a DPDT switch? I need a mini motor for a cosplay project so it can spin both clock and counterclockwise.
Jordy Brusselman says
Ooh god you dont need to approve my previous message. I was on the wrong page. I thought I was on the buying page. Sorry for the trouble :p
Swagatam says
No problems!
MAnoj Cracked says
Can you please tell me where to connect those relays … I mean are they directly connected to 12v DC supply…??
Swagatam says
yes both the relay coils are connected between +12V and the transistor collector
Anonymous says
can you please tell me Why diode is used there??
Swagatam says
it's for protecting the transistor from relay coil back EMF
Kousik Singha says
Hii sir, please help me how i can make automatic rain sensing wiper motor control using 555 timer ic
Swagatam says
Hi Kousik, you can refer to the following article
https://homemade-circuits.com/2012/09/rain-triggered-instant-start-windshield.html