3pi robot suddenly powers down

I’ve been experimenting with the Sharp distance sensors, connected to AD7 and PD5. Reading the sensors work quite well but as soon as I engage the motors as well, using code from the example sketch OrangutanMotorExample. the 3pi will run for anything between 0 and 10 seconds and the suddenly power off.

The batteries (4xAAA) are new and the battery voltage reading seems fine. Can it be the combination motors+Sharp sensors that leads to the power off? If I do need some more power, how can I achieve that? I mean, I can mount a 9V cell somewhere but how to connect it without destroying anything?

I probably should mention that I have installed the Sharp sensors following the instructions in the ‘wall following’ project.

Hi Dag,

While I cannot confirm that the combination of the two is the cause of your problem, I can certainly say that I have experienced many a sudden shut down running only the motors, when using anything other than NiMH rechargeable batteries. If you aren’t already using those kind of batteries, I would recommend it. What battery voltage does your 3pi report?


The 3pi reports around 4V which seems a bit low, 4xAAA should be 6 but is the report the full voltage or 2/3, as the docs say about AD6?

Anyway, now using Duracell non-rechargeable, all I had lying around. Have ordered proper batteries which I will get tomorrow, curious to see if that will improve matters. Will report back in either case :slight_smile:

The read_battery_millivolts_3pi() function reports the correct voltage, since it takes into account the 2/3 voltage reading from ADC6. Using this function will give you the correct voltage.

Yeah, 4V is quite low. Usually, I recharge at about 4.8V. That way I don’t risk my 3pi powering off during programming. Let us know how the new batteries work out. :slight_smile:


New batteries, newly charged and the thing runs like mad :slight_smile:
Lesson learned: batteries matter!!

Thanks Geoff.

No problem, happy to help.