Controllers in series

I currently have a high voltage simple motor controller working with autohotkey controlling a single motor. I want to add two independently controlled micro motors to this setup, and still be able to control all of them through autohotkey. Do I simply need to buy two more of the same boards and connect them through the tx connection? Or can I use a cheaper serial motor driver board for the smaller motors and achieve the same thing?

The Simple Motor Controller’s TX line can not be used to transmit bytes from USB, so it won’t work the way you want it to. What you could do instead is connect all three of your motor controllers to the computer via USB. Then you can use the “-d” option of SmcCmd to specify which controller to communicate with.

Alternatively, you could get a USB-to-Serial adapter and use that to control all three Simple Motor Controllers. Many of our products, such as the Pololu USB AVR Programmer, Maestro, Jrk, Orangutan SVP, and Wixel can all be used as USB-to-Serial adapters, so if you have one of those you could use it. This would require you to write some serial code on your own though, because SmcCmd command uses a direct USB connection.


Thanks David. So I will probaby go for the first example you give. Do you guys offer motor controllers that can control more than 1 motor? Of would I have to just purchase 1 of these for each motor?

Also, where can I find more information about the -d option in assigning IDs to each controller? Thanks!


Some controllers can do only one motor and some can do two. All of the Simple Motor Controllers are only one channel; the qiks are dual-channel controllers.

From the windows command line, if you type “smccmd,” you can see the help for it. Here is the output:

SmcCmd: Configuration and control utility for the Simple Motor Controller.
 -l, --list                   list available devices
 -d, --device SERIALNUM       (optional) select device with given serial number
 -s, --status                 display complete device status
     --stop                   stop the motor
     --resume                 allow motor to start
     --speed NUM              set motor speed (-3200 to 3200)
     --brake NUM              stop motor with variable braking.  32=full brake
     --restoredefaults        restore factory settings
     --configure FILE         load settings file into device
     --getconf FILE           read device settings and write to file
     --bootloader             put device in bootloader (firmware upgrade) mode
Options for changing motor limits until next reset:
     --max-speed NUM          (3200 means no limit)
     --max-speed-forward NUM  (3200 means no limit)
     --max-speed-reverse NUM  (3200 means no limit)
     --max-accel NUM
     --max-accel-forward NUM
     --max-accel-reverse NUM
     --max-decel NUM
     --max-decel-forward NUM
     --max-decel-reverse NUM
     --brake-dur NUM          units are ms.  rounds up to nearest 4 ms
     --brake-dur-forward NUM  units are ms.  rounds up to nearest 4 ms
     --brake-dur-reverse NUM  units are ms.  rounds up to nearest 4 ms[/code]

- Ryan

Edited to refer to SMCcmd instead of USCcmd.


You should note that the AutoHotkey approach will only work with those controllers of ours that have integrated USB, as those are the only controllers for which we have written command-line interface software (like SmcCmd). If you use something like our qik serial motor controllers, you will need a USB-to-serial adapter to connect them to your computer, and you will need to write your own interface software to send the appropriate serial commands to the board. If you’re happy with your AutoHotkey solution, I suggest you just connect three Simple Motor Controllers to your computer via USB. The Simple Motor Control Center software makes it easy to assign distinct device IDs to each SMC.

You can find out more about our offering of motor controllers here:

- Ben

Yeah I picked up on that after reading about the serial boards you offer.

So basically there’s only two offerings for Autohotkey USB interface, both with single motor control?

How come something like the TReX board doesn’t offer USB support with multiple motor channels? Is this a limitation of USB or you guys just haven’t programmed an interface for one yet?

Making a TReX-like controller with integrated USB is certainly on our to-do list, but it’s probably still quite far off (our to-do list is pretty long!). We designed the Simple Motor Controllers to be chainable, however, so you can fairly easily add control of as many motors as your system requires (e.g. I know of at least one customer using six in an underwater ROV). One benefit to using individual SMCs is that you have more flexibility in driver selection and placement.

- Ben

Okay, you’ve all helped me immensely. A few more questions however…

What is the smallest motor I can run with the SMCCMD simple motor controller board?

For instance can I run the 6 V metal micro gearmotors off of it? or is the output too high @12V? Is there an easy way to reduce the output of these boards?

There is no notion of “smallest motor” for the Simple Motor Controllers. Your main concern with pairing a motor controller with a motor is ensuring that the controller can deliver the current the motor will draw while operating over an appropriate voltage range for the motor. All of our Simple Motor Controllers will work with our micro metal gearmotors, so I suggest you go with the least expensive model: SMC 18v7.

If using a 6 V power supply is not an option, you can always restrict your SMC motor speed (e.g. limit your maximum speed to 50% when using a 12 V power supply). Note that our micro metal gearmotors can be run at higher voltages, however (we power them at 9.25V on the 3pi robot). Higher voltages tend to shorten the life of the motor.

- Ben

Perfect. I will be using a 12V connection from a computer power supply. The spur gear I plan to use the motor for needs to turn super slow anyway, so 20-30% speed is completely doable for the mechanics. It’s also only on for a 90 degree rototation then killed with a limit switch. I think I have the information I need to spend some cash on your website! Thanks again guys.

If you don’t need a lot of speed, I suggest you go with a high gear ratio of a non-HP micro metal gearmotor. We just recently added some extremely slow 1000:1 gear ratio versions that you might be interested in.

- Ben