Choosing motor controller for rover

Hi! This is my first post here. My first Arduino boards (Uno and Mega) just arrived yesterday! I am new to robotics, so please excuse my ignorance. I would greatly appreciate if you could explain your reasoning as well, so that I can learn to make my own decisions ...

Background:
I am building a rover to mount my camera, for wildlife photography. Given the nature of the work, it will involve short distances with plenty of starts, stops and maneuvering.

I have purchased a Dagu Wild Thumper 6WD chassis, and there is some confusion about its motors. Pololu states that each motor has a stalling current of 6.6A, and since there are 3 motors per channel, they recommend a motor driver capable of 20A per channel.

However, the manufacturer specs state that the locked rotor current is 5.5A. The continuous current required is not stated, but I assume it will be about 25% of that. If my reasoning is correct, I shouldn't need more than 5A of combined current per channel (for 3 motors).

The problem:
Firstly, I am unclear on what the specs of my motor controller should be (I'm restricting myself to dual-channel controllers). Should I go for a controller that supplies 25A, 30A etc.? Or can I do just fine with a controller that supplies 10A or 15A continuous, with a peak of around 30A?

It's a problem of cost:

  1. Sparkfun Moto Shield supplies 14A continuous, 30A peak, but costs $70. I'm not sure if 14A is enough for a 6WD (based on Pololu's recommendation)

  2. Sabertooth offers a powerful $125 controller with 25A continuous, but I wonder if this will be overkill (and needlessly expensive). I've seen some Youtubers using this controller, but I don't want to go this route if it isn't necessary.

  3. At the other end of the spectrum, there are these super-inexpensive Chinese controllers...
    ... Like this $25 15A (30A peak) controller, with heatsink and all
    ... Or this one that merely states a 30A figure and costs only $16. :o

It's the price that's a little disconcerting. Since I am a newbie, I can't tell if there have been any compromises in quality. Of course, I'd rather spend $20 instead of $70 or $125. :slight_smile: What's the catch?

Final thoughts...
What other features should a motor controller have? There are some that offer RC control. Is this a deciding factor? I think that RC will be my only feasible option in the wild, vs. wifi or bluetooth. Does it really matter if the MC offers radio control?

And will I need a 2nd controller for video feed (so that I can steer the rover remotely)?

If you've read this far, thank you for your patience! I look forward to your response. As I said, I am totally new to this, so I highly appreciate all your help and advice!

Thanks Delta_G for your advice on video.

Regarding the motor controller itself, I'm unclear on how much power supply is required. Is continuous current only a fraction of stalling current (say, 20-25%, as I read somewhere), or it is better to have the motor controller be as capable as possible?

Meaning, for 6 motors (3 per channel) with 6.6A stalling current, should per-channel current be around 20A, or would something like 7A be enough for it?

My apologies, if I am asking the question in the wrong forum.

Hobby King sell a variety of Electronic Speed Controllers (ESC) for DC motors that are used by model planes, boats and cars. I think there are models that are cheaper than the prices you mention. Be aware that not all of the models provide for reversing the motor (not needed in a model plane).

Also be aware of the difference between a brushed DC motor and a brushless motor. They need very different ESCs.

I would be content with a motor driver or ESC that can handle a bit more (maybe 20% more) than the motor stall current OR a driver that automatically shuts down when overloaded.

Another idea, if you are using motors with a 5 amp max you might like to consider using the Infineon TLE5206 driver chip which has overload shut down.

...R

Thanks for your advice, Robin2! Much appreciated. :slight_smile: I'll have a look at the products you mentioned.

Are the motors directly driving the wheels? If not you need to factor the gear reduction ratio into the motor decision. If geared down enough, the motors may never even approach a stall current.

Paul

Hi Paul,

My motors have a 34:1 gear ratio. There are compatible 75:1 motors available. At 7.2 V, my motors have a stall torque of 5 kg-cm (70 oz-in), whereas the 75:1 motors stall at 11 kg-cm. I'd love to know how gear ratio affects choice of electronics, in case I replace motors in the future.


For now, I am considering the Pololu 18v15 controller, which seems to offer a nice balance between cost and capability.

There are many less expensive options out there, but since I am new to this, I cannot judge the quality of a product from photos or description. It would be nice to have access to a support team, in case something goes awry.

Pololu also offers free software for configuring their controllers. I'm not sure if this really matters.


I'll have to make a decision soon. I'm so grateful for everyone's advice! Thank you!

If my reasoning is correct, I shouldn't need more than 5A of combined current per channel (for 3 motors).

Your reasoning is wrong and Pololu's recommendation is correct.

Brushed D.C. motors briefly draw the stall current every time they start up, so you need a motor driver capable of handling at least 36.6 Amperes (or 35.5 A if you accept the manufacturer's claims) for the Dagu Wild Thumper.

The 18V15 may be enough for your project, but the peak current handling capability does not seem to specified. You might post on the Pololu forum to ask about it.

I like the Sparkfun option. I use those chips and their successors in a lot of different projects. I have never blown one up.

30A peak is more than you need, so it is safe.

The cheap Chinese devices are probably sufficient. You don't need 25A continuous even if you are climbing hills all day.

Thank you all for your ideas and support! I purchased a Roboclaw 2x15A motor controller and am making good progress on my project. It has a peak current of 30A per channel. I also like the fact that with it, I can test my prototype using their Ion Studio software over a USB connection. Cheers!