I’m trying to put together a little rover based on the DFRobot Turtle 2WD platform, using an Arduino Uno and the RB-Dfr-583 rover mobile robot shield.
The Turtle comes with a compartment for 5 AA batteries, so I’m trying to use that as a power supply for the shield. According to the documentation, that should be possible, even though the recommended way is apparently to use a 3.7v LiPo.
I don’t have the parts to put a plug on top of the battery cables, and connecting the battery to the shield’s VIN didn’t seem to provide power to the motors. I suppose that’s passed through to the Uno directly.
Next to the LiPo connector, I found two little holes labeled “+” and “-” I could solder pin headers into I suppose. Feeling adventurous, I simply connected the batteries’ cables directly into those holes, which of course doesn’t provide the same contact as if I had soldered them (or used pin headers).
That actually seems to have worked: The little program from the documentation actually made the wheels spin. However, what also happened is that some smoke started to arise from close to where I had connected the battery cables. I’m not entirely sure what happened there since I’m not so good with electronics, but before I try to solder on pin headers in vain - would that even work? How could I connect AA batteries to the correct input on this shield to power the motors?
Next to the LiPo connector, I found two little holes labeled “+” and “-” I could solder pin headers into I suppose.
Bingo.
However, what also happened is that some smoke started to arise from close to where I had connected the battery cables.
That’s not good. Can you take a close look at all components and see if you can spot what might have burnt? Was there a chance the leads from the battery contacted something on the board, or each other?
I had a closer look, and couldn’t see any damage. Then I tried it with a 3.7V LiPo battery that arrived in the mean time - works just fine. Then I got adventurous again and tried it with the AA battery compartment again, since you confirmed that I used the correct pin holes. This time there was no smoke! So maybe last time I connected it, I did something wrong, or maybe there was some kind of residue there that’s gone now, suppose I won’t find out.
One more question: I noticed that with the AA batteries, the motors seem to spin faster, which doesn’t make a lot of sense to me. The amperage of a 3.7V LiPo and that of a AA battery seems to be about the same from what I can find (1-2), and the voltage is only about 1.5V… Is this something to worry about, in terms of overstressing the shield or the motors? Or just some electronics I don’t understand?
I noticed that with the AA batteries, the motors seem to spin faster, which doesn’t make a lot of sense to me. The amperage of a 3.7V LiPo and that of a AA battery seems to be about the same from what I can find (1-2), and the voltage is only about 1.5V
It’s likely that the 5xAA pack has the batteries in series, which would be 5x1.2V (rechargeable) or 5x1.5V (alkaline), so between 6V and 7.5V, whereas a single cell Lithium battery is 3.7V. It’s likely the motors on your platform operate best at 6V. The higher the voltage, the faster the (max) RPM.
