I’m working on an obstacle avoidance robot using the Arduino with the motor shield from ladyada (pololu.com/catalog/product/1098) which are rated at 6 volts. 6 volts would be 5 AA NiMH @ 1.2v/battery, but I can’t fine any 5 cell battery holders. So my question is should I just under power it with 4 AA, over power it with 6 AA, or daisy chain a 4 cell and 1 cell battery holder together? Any other tips appreciated! Thanks!
Hello.
The motor driver on that board is relatively crappy, so you’ll lose some voltage in it; therefore, I would definitely go with at least the 6 cells (7 or 8 might be better) on the motors, and use that for the Arduino, too. You could then use a separate 4-cell pack for the servos. By the way, you can also get to 5 cells (if you still want to go that route, e.g. for the servos) using a 3-cell holder and 2-cell holder, so you should go with whatever you think might be useful in future projects.
- Jan
Thanks for the reply! That’s helpful. Are you saying I should use just 1 battery set of 6 for the whole robot instead of 1 set for motors and 1 set for the arudino/sensors/servos?
Didn’t know that motor driver isn’t so good. I got it because I’m just getting into the Arduino and thought that’d be an easy way to start playing with the Arduino and motors. But in the end I may only have 1 or 2 servos and 2 DC motors so that motor shield may be overkill and I’d be better suited with a different motor controller. Thanks for the tips!
No, six cells can be too much for a servo, so you’ll probably need a separate supply for them. If the batteries are a concern, it might be easier to look for a servo that can handle six cells, though that is often not specified by the servo manufacturers.
The L293D (and similar SN754410 from TI, which we sell) should be okay. They’re just old parts that have been around for a while; newer parts, like the TB6612, have higher performance, but they tend to be available only in surface-mount packages. I don’t know anything about the Lady Ada product, but if it’s a kit, the availability of the part in a through-hole package is probably why she used it.
- Jan
Oh I think I left out a key part. The servos will be connected to the 5v regulated power from the Arduino. I’ll have 6 AA powering the DC motors (pololu.com/catalog/product/1040). All it’ll need to do is turn a Sharp IR range finder for obstacle detection. I’m think this should all work together. Let me know if you have any suggestions.
I was looking around at the motor drivers and controllers you offer. I’m thinking for my next robot I’ll go for the Qik 2s9v1(pololu.com/catalog/product/1110). That looks like a slick way to easily get 2 DC motors going and then I don’t have to use this motor shield anymore.
Thanks for all your help!
Powering servos through a regulator is generally not good unless you know what you’re doing, but you might be able to get away with it if you’re just using two really small servos.
- Jan