View Full Version : [Question(s)] 6(+)A motors with arbotix?

03-21-2011, 06:57 PM
I'm starting my build for MW'12 and have hacked a 9.6v battery operated reversible drill for one of the two motors I'll be using (to power the caterpillar treads), and have tentatively tested the amperage draw to be ~6.7A. That was with the battery as-charged right out of the box; I'm charging the battery now and will test again with a full charge in order to ascertain the upper load levels.

Assuming I've tested the amperage loading correctly, is there a way to still use the arbotiX, and it's 1A motor/encoder headers, with two of these motors?

As for testing, the motor bogs way down when I apply the test leads to the contact/load leads of the motor, while fully depressing the power switch. Is that normal? My apologies, but I won't have the photo's I took today (even though they're erroneously date/time stamped as of 04/18/2015) available for posting until tomorrow.


03-21-2011, 09:20 PM
Update: The good news is that I figured out what I was doing the wrong with the multimeter (testing in parallel of, instead of in series with the motor's wiring), but the bad news is the motor is still pulling above the 1A threshold of the arbotiX, at ~3.8A.


03-22-2011, 10:37 PM
The pics as previously mentioned. Please excuse the breakfast nook table top that's substituting as my workbench, as I have yet to setup a workshop area.

Ryobi 9.6v drill, new-in-box.

http://www.stobscorner.me/index.php?supermode=gallery_view&previewm=1&a=Hacks&image=110322095333_100_5505.25.jpg&screenres=1024-600http://www.stobscorner.me/index.php?supermode=gallery_view&previewm=1&a=Hacksâ„‘=110322095333_100_5502.25.jpg&screenres=1024-600 (http://www.stobscorner.me/index.php?supermode=gallery_view&previewm=1&a=Hacks&image=110322095333_100_5502.25.jpg&screenres=1024-600)
The drill unpacked - felt a bit like Christmas! lol

At first glance it seemed like there were only eight obvious screws holding the housing together, which proved to be true. If you look closely at the chuck you'll see that it's spinning, as I wanted to ensure that the drill was operational before I started to disassemble it.

The housing came apart quite easily, with no hidden fasteners or placement of adhesives.

Simply a close-up prior to dislodging any of the components, anticipating a reference source for re-assembly.

Wha-La! Looks nice and compact, even with the chuck still attached. I won't be taking that off until I'm sure I'll be able to utilize the motor as planned, otherwise I'll just re-assemble it and add a light-weight drill to my toolbox.

I realize this was a bit "Rube Goldberg (http://en.wikipedia.org/wiki/Rube_Goldberg)," but I couldn't wait to setup a jig before testing the motor outside of the housing. I know, I know - but that's just the way I am, I had to know for sure that it would run outside of the housing! For this pic I just had the motor assembly fitted into a cradle I'd cut into the drill's packaging, and held the camera upside down so that I could shoot the pic with my left hand.

I have to say that I was pretty happy to finally get started on building something, but I definitely need to ratchet up the professionalism - with a decent workbench high on the list and a better camera/video setup down the road.

I did some web-surfing last night on motor shields, as I'm guessing at this point that's the way I need to go, but I'm not sure I'll find an OTS product that will be suitable. Any assistance in this matter would be greatly appreciated.


03-23-2011, 09:49 AM
Assuming I've tested the amperage loading correctly, is there a way to still use the arbotiX, and it's 1A motor/encoder headers, with two of these motors?

You won't be able to use the installed motor drivers. However, you can certainly add external motor drivers. For instance, this post (http://forums.trossenrobotics.com/showpost.php?p=43193&postcount=1) shows how to interface a pair of 30A motor drivers to an ArbotiX, and drive them using our "BigMotors" library.

Other driver configurations are certainly possible, but will require you create your own library/interface software. You could connect to the existing PWM pins (by pulling the motor driver chip and pushing wires into the socket of the chip), and then modify the Motors2 or BigMotors library to match your new motor drivers.


03-23-2011, 11:01 AM
Thank you very much for your timely reply Fergs, greatly appreciated!

I performed various searches using the terms "10A", "motor" and "shield" but didn't come across anything from Pololu, and that looks to be about a perfect match. My work-mate helped me test the motor under high load this morning and it looks like the peak load amperage is just beyond 12A. I'll still make a jig to hold the motor in place for testing, but this at least gets me into the right ball park. Thanks again!