Recommended motors for use with L298 motor controller

NETMF & Gadgeteer
1

Hi guys,…

I am graduating from the yellow plastic 5$ dagu motors, for my robot.

I’m looking at various websites, comparing motors, and trying to find a good fit.

I want to power my bot with 12v (actually an 11.1v 5000mah lipo that I have), and I am using two GHI L298 motor controllers, to drive 4 motors, each with 4" Vex mecanum wheel)

I see that they are rated for up to 3A motors, and I assume that means -each- motor if each L298 is driving two.

So, Am I correct in that I need to make sure that the “stall current” does not exceed 3A when selecting a motor?

I’m also looking for some reasonable power out of a small (<=37mm diameter, <=60/65mm long) and somewhere in the 100-160rpm range.

It is a baffling experience navigating through the various websites (robotshop, dfrobot, robotmesh, etc) since you cant filter based on these parameters, and so nothing is sorted. I’ll find something that looks good, drill down and see “oh, 5A stall current” or “80mm long” etc.

It’d be nice to have integrated encoders, too.

I almost bought these:
http://www.robotshop.com/en/pololu-12v-50-1-gear-motor-encoder.html

…they matched everything except the stall current. I’m still considering them, and just being very diligent about watching the encoders to shut them down if they stop turning, to prevent a stall… but Im not sure how reasonable an expectation this is.

Can anyone chime in with advice? I imagine the total weight of the thing would be about 3-4 lbs (1.5-2 KG). Any other gotchas I need to consider?

Also, I am in New Zealand, so stuff takes forever to get here, and shipping is often very high…

Also, Vex makes some motors and motor controlelrs too, but for their own proprietary system…has anyone used vex motors with the L298 controller module?

2

You might want to check out

Micro motor research & development – all about maxon | maxon group. That’s their Australian web site which I’ve never used. The company is based in Switzerland (I think) and I use their US web site. Should be the same products though.

or

You can search by size, torque and a bunch of other ways. They aren’t cheap, but if you start with either one of those companies you should be able to get a better idea of what you’re looking for and then maybe you can find a cheaper alternative.

Make sure you’re looking at brushed DC motors, not brushless motors which I’m pretty sure won’t work with the motor controller you mentioned…

As far as sizing a motor by matching the stall current to the motor drive rated current, that may not be the most effective way to do it depending on your application. Both the sites I mentioned have really good app notes describing how to size a motor for a given load application. The “Maxon Academy” part of their web site is particularly good. Usually you size the motor based on the torque and speed you need to deliver and then pick a motor controller that can deliver the required current plus a little more.

Good luck

3

Thanks Gene

Well, this is a hobby, not a career. I don’t think I need super expensive motors. Those websites look like they aim just a little higher end than I need :slight_smile:

I already have my motor controllers:

https://www.ghielectronics.com/catalog/product/315

I just want to be able to move my robot car around nicely with the controllers and wheels and power that I have, without blowing up the controllers in a stall. The cheapo dagu motors I have are just a bit weak.

Too many variables for my tiny brain.

4

@ mtylerjr - What did you buy?

I’m looking to get some of these 34:1 Metal Gearmotor 25Dx52L mm LP 6V with 48 CPR Encoder ( Pololu - 34:1 Metal Gearmotor 25Dx64L mm LP 6V with 48 CPR Encoder (No End Cap) ) and I do hope they will work nicely as these will be for my Gadgeteer and DC Motors hands on lab. I’m planning on powering them with a 5v wall wart as I really don’t want the L298 chips getting too warm.

I’m looking at getting these for the stepper motor hands on lab Stepper Motor: Bipolar, 200 Steps/Rev, 35×26mm, 7.4V, 0.28 A/Phase ( Stepper Pololu - Stepper Motor: Bipolar, 200 Steps/Rev, 35×26mm, 7.4V, 0.28 A/Phase ) and also planning to power these with the 5v wall wart above and using Big Easy Driver Stepper Motor Controller ( http://www.robotshop.com/ca/en/big-easy-driver-stepper-motor-controller.html )

and for the servo lab some HS-422 Servo or HS-425BB Servo, I’m just not sure the HS-425BB Servo are worth the extra couple of bucks as I’m buying 12 so I can setup 12 project boards per lab.

5

Hello!

I ended up buying 4 of these these:

They work really nicely with the l298 module. Basically half the speed, but twice the torque, slightly less stall current, of the ones you linked to.

I used them with these wheels:

http://www.robotshop.com/en/mecanum-wheel-set.html

Which are awesome. Easy to move laterally, diagonally, spin in place, etc.

6

@ mtylerjr - Thanks that takes a load of stress off my mind as now I’m feeling a whole lot more confident about using these motors for my labs. Next question is are you wishing you had more speed or torque? I will use these motors to build different devices when I’m not using them for teaching so I’d like to put mecanum, tracks, regular wheels etc on them, but they also need to have enough whrrrrr on them to keep a student interested, so the minor question is the 34:1 a nice all around speed/torque ratio?

7

The rover I am building, I wanted to make sure it was robust, and could move through uneven terrain (grass, etc) and carry whatever sensors/servos/robotic arms I couple put on it - so I sacrificed speed. Torque was more important to me. That’s why I went with the 75:1. I’m sure the 34:1 will be good, too.

I actually run my motors using a 11.4v Lipo. I split the power with a dfrobot adjustable power module : http://www.dfrobot.com/index.php?route=product/product&product_id=752

… and use its 9v (the adjustable voltage side) for the motors, and its 5v (fixed voltage side) for the main board+modules.

I used an additional little step down module from the 9v to feed 5v to some small servos as well (to keep the motors/servos off the same line as the mainboard to prevent spikes/resets etc)

http://www.ebay.com/itm/2PCS-Input-6-5-12V-AMS1117-5-0V-Power-Supply-Module-Voltage-Regulator-5-0V-/400710769487?hash=item5d4c391b4f

I like those little dfrobot adjustable power modules.

8

@ mtylerjr - Thinking about your comments I think I’ll drop one in gear ratio and order this one instead as the higher torque might be a better idea

47:1 Metal Gearmotor 25Dx52L mm LP 6V with 48 CPR Encoder

I’m looking forward to getting all these and doing some classes around robotics and different motors, but I’m already thinking of projects I could do with all these motors as well, the possibilities are just way to fun.

Thanks