Let's Make Robots!

Big Motor Driver (Inspired by Chris the Carpenter)

High-Current Motor Driver

I'm not sure how I stumbled upon this site but find myself visiting it on a daily basis now.  I spent the better part of a week reading through a numerous amount of posts and became inspired by some of the designs.

One design that caught my interest was the motor controller made by Chris the Carpenter (with contributions from others).  So, instead of mooching information off of the site I decided I should contribute something.

I have posted a motor controller design that is supposed to be simple, robust, cost effective, and able to handle high currents.  Above is a schematic of the first part of the design.  I will post an updated version to include a PIC to accept commands from a PC, Microcontroller, etc. and provide the direction/PWM signals to the H-bridge.  I am still working on the PCB but here is what I have done so far for review/critism.  What is not shown in the schematic are the in-line fuses for protection.

For the PIC, I use MBasic and PicBasic Pro to write the code.  This should convert easly to the BS2 and PicAxe.

More to come and thanks for whatever welcome I may receive (hopefully a warm one).


** Updated 04 January 2009 **

Here is an updated version based on advice provided below.  Again, if you find any errors let me know.

Thanks to all who provide help/advice and to those who show interest.  I know there are easier ways to do this but this is sorta an addiction now.

Updated controller


** Updated 10 Jan 2009 **

 I updated the schematic again.  As suggested I changed the MOSFET driver to a TLP250 and dropped the 1K resistor across the Gate to source.

Update the schematic to show that the logic grounds are isolated from the dirty motor grounds.



** Updated 10 Jan 2009 **

Updated the schematic for those that want to save an I/O pin.  There is a Hex Inverter/Buffer circuit (U1) that feeds the inputs of the Optoisolator (U2).  If you look at the wiring for the Hex Inverter you will notice that the output of the second inverter feeds the input of the first inverter.  So, when a logic 1 is placed across pin-3 it is inverted into a logic 0 which turns off the Reverse Relay.  A logic 0 is also placed at the input of the first inverter which gets converted to a logic 1 on its output and turns on the Forward Relay.

By using the inverter circuit you will no longer have the capability for dynamic breaking.  In other words, one of the relays will be active as longs as powered is applied to the circuit.  Disabling the PWM signal will keep the motor from turning.



** Updated 11 Jan 2009 **

Finished the PCB design.  Once boards are complete will test and post schematic and board files once any kinks are worked out.



** Updated 22 January 2009 **

I got the prototype boards back from the manufacture two days after I sent them off.  As you'll see below, the quality is excellent.  Tonight I populated the board and checked out functionality with a multimeter prior to testing with a motor.  I managed to get everything put together right so on to the smoke check.  I hooked up a good size motor with a lot of torque and applied power.  The motor moved in both directions and the MOSFET did not even get warm.  This test was applying full power to the motor and not PWM.  Next, I'll write some code and test functionality with PWM hooked to my Oscope so I can check the signals and see how high I can take the frequency.  I'll get around to posting some video but, in the mean time, here are some pictures of one of the finished boards.


PCB Bottom








** Bill Of Materials **

Component Description Part Number Vendor Cost
C1 220 uF P10325-ND Digikey $0.72
C2 0.1uF BC1114CT-ND Digikey $0.20
D1 1N4001 Rectifier 50V 1A 1N4001DICT-ND Digikey $0.30
D2 1N4001 Rectifier 50V 1A 1N4001DICT-ND Digikey $0.30
D3 Schottky Diode 45V 15A STPS1545D Mouser $0.80
D4 Schottky Diode 45V 15A STPS1545D Mouser $0.80
D5 Schottky Diode 45V 15A STPS1545D Mouser $0.80
D6 Schottky Diode 45V 15A STPS1545D Mouser $0.80
J1 4-Pin Header, Male 2077095 Jameco $0.19
J2 Screw Terminal, 2-Pin 160785 Jameco $0.65
J3 Screw Terminal, 2-Pin 160785 Jameco $0.65
J4 Screw Terminal, 2-Pin 160785 Jameco $0.65
LED1 3mm Red, T1 253278 Jameco $0.26
LED2 3mm Red, T1 253278 Jameco $0.26
LED3 3mm Red, T1 253278 Jameco $0.26
Q1 2N2222 NPN Bipolar Transistor 600mA 75V P2N2222AG Mouser $0.21
Q2 2N2222 NPN Bipolar Transistor 600mA 75V P2N2222AG Mouser $0.21
Q3 IRFZ44N Single-Gate MOSFET Transistor N-Channel 60V 50A IRFZ44NPBF Mouser $1.30
R1 270 Carbon Film 1/4W P270BACT-ND Digikey $0.08
R2 270 Carbon Film 1/4W P270BACT-ND Digikey $0.08
R3 270 Carbon Film 1/4W P270BACT-ND Digikey $0.08
R4 1K Carbon Film 1/4W P1.0KBACT-ND Digikey $0.08
R5 1K Carbon Film 1/4W P1.0KBACT-ND Digikey $0.08
R6 10K Carbon Film 1/4W P10KBACT-ND Digikey $0.08
R7 10K Carbon Film 1/4W P10KBACT-ND Digikey $0.08
R8 39 Metal Film 1/4W 39.2XBK-ND Digikey $0.11
RLY1 SPDT 12V @ 20A ACT112 Mouser $2.17
RLY2 SPDT 12V @ 20A ACT112 Mouser $2.17
U1 PS2501-2 Dual NPN Phototransistor PS2501-2-A Mouser $0.87
U2 TLP250 Photocoupler IGBT MOSFET Driver TLP250F-ND Digikey $1.88
PCB Printed Circuit Board N/A
ExpressPCB $20.28

** 24 January 2009 **

I added a few of pictures of the test application and the temporary PWM controller used for testing.

Test Application

Temporary PWM Controller and Motor Controller


** 02 February 2009 **

Added a crappy video of the motor controller being tested.

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I said screw it... a friend bought me a sabertooth 2x25 25A motor driver from DE... time>money

Good choice for a controller.  I just got home this weekend and I made a video yesterday after watching the super bowl, rewrote the test application, finished making a bench power supply so I can get rid of the batteries for now and worked more on the microcontroller code.

Good choice on the Sabertooth as it is very reliable.  I've used those before and with this project I decided I wanted to have more control over the design so, everything gets designed/built by me.  Also, I'll be able to use the designs for other projects.  I'll still post everything as others may want to use them for ideas.

Good luck with your project,


As a bad programmer, you should understand the "snippet" funtions soon. I promise if you try, and follow all the directions to something like pallax's BoE bot. you Will learn to code. The amp/hr (Ah) rating of your battery determines the amount of time your pack will output at hours rate. locked rotor current can be as high as 10xAmpre rating! 30 motor ...300A inrush. I always rate relays 125% of the load. the voltage is not so important when it comes to relays and fuses. Till seeking a 36v(nom) 1hp(30A) motor controller for my scooter. BTW regenertive braking is lousy...at best in anything. soooo..much loss... heat loss, friction loss, copper loss. I'm sure that regen returns 10% of you power.
Very nice set-up my friend... I can't wait to see what comes of these motors and wheels. I just watched the ramp-up ramp-down video and again, a nice set-up. --I think I heard a dryer in the background, anywhere you can have that nice a shop IN YOUR HOUSE, is awesome!!
So have you used this board in a robot yet? I like it!
I redesigned the board to include a dedicated controller.  I'm also slowly working on the platform that it will be included on. It has been slow coming as I have a lot of other projects that I'm trying to finish that will be used for the bot also.  It's kind of like one project affects the other.  Currently, I'm finishing up my CNC machine that I want to use to cut out parts for the bot. That has been taking the bulk of my time. I've also been working on documentation for the other projects. I really need to update my progress.