Created by
Created March 01, 2012
Last modified March 02, 2012
Tags 555   555-motor-controller   astable   bjt   cheap   dfiction   econo   flyback-diode   motor   pwm  


555 oscillator easy motor control. not so stable. very effective.


well, here's a pretty simple 555 astable oscillator. the pot just controls the duty cycle of the oscillator, and d1 lets you bypass "R1" (between discharge pin and threshold) in order to bypass the charge cycle and get a <50% duty cycle.

r2 is arbitrary, and the bjt could be any type.

i built this in real life, of course, before drawing out the schema here.

the oscillator isn't that stable, but for a DC motor controller under 50ยข, this does the trick.


Hi, I'm trying to build an ROV and I plan to use 12V 1.2A bilge pump motors for the thrusters. I have an Arduino UNO microcontroller that supports PWM output on some of it's pins and I was planning on using that to give an analog like control over the motor speed. Problem is the Arduino's PWM outputs max out at 5V at 20mA, and the motor needs 12V at a much larger 1.2A. Would a circuit similar to this one utilizing a BJT do the trick? If I replaced the 555 Timer set up with the Arduino to provide the PWM signal and a 12V input instead of a 9V on the motor side would that work or am I way off? I'm still learning about this and would really appreciate any help you could give me. Thanks!

by finnigan16
March 01, 2012

wow, the community support here is CRAZY! can you believe that this site just started and already i'm talking to a stranger about circuits?!?! so cool!!!

anyway: you're absolutely right. use a diode to protect your transistor from an inductive load.

by danielfiction
March 01, 2012

Haha, Yeah I pretty much just started this project and coincidentally this site launches. Talk about timing! Anyway, thanks a lot for the help! As soon as the motors arrive in the mail I'll wire it up and let you know how it goes.

by finnigan16
March 02, 2012

Hey, im thinking to use that power transistors from that atx power supplies. Its a hi speed switching transistor. what do you think? Stable?

by jhonalvez
May 18, 2012

hey ,

how well do you think this circuit will work against a 130V DC motor , what kind of stability issues can we get ? and are they ways to avoid it in this circuit

cheers arjun

by scyther
October 25, 2012

Leave a Comment

Please sign in or create an account to comment.

Revision History

Only the circuit's creator can access stored revision history.