Power

[grangep]

Hi, I'm looking to build a robot using a Rpi and an Arduino. The Co-op looks like a good way to do that, but I'm a little confused about power. Most Arduinos seem to have a linear step-down voltage regulator to take the battery voltage down from typically 7.2 to 5, but the co-op runs from 5, correct?
The manual talks about running the Rpi from a voltage regulator attached to the Co-op, but the diagram looks like the Co-op is powered from the Rpi. Do I just plug the Co-op on to the Rpi & that's it? It that's so I just need an external 5v regulator (again assuming a 7.2v battery supply) for the Rpi?
One more thing if I may, there does not seem to be a physical fitting to the Co-op, just the plug, have you experienced any problems with vibration in a robot environment?

thanks, pete.

[Alan]

Hi Pete,

Thanks for the question, and welcome to the forum.

The Pi Co-op doesn't have a voltage regulator on board, so what I was trying to say in the manual is that if you have a 5V supply (from another voltage regulator) then you could plug it into the Pi Co-op, and then have it power the Pi. This could be useful in situations where you have a wire carrying 5V, but no micro USB connector. The Pi Co-op has a resettable fuse on the power line so if there was a current surge on the powerline then this would protect your Pi. You are correct, that to run the Pi Co-op and Pi from a 7.2v battery pack you would need a voltage regulator.

With regards to attaching it to the Pi, if you look at the attached picture of the bottom of the Pi Co-op then you'll see that there's a rubber bumper. This sits on the capacitor near the micro USB port and gives stability.

Depending upon the type of robot you're building, have you looked at the Dagu Mini Driver we sell? You can find details of a Raspberry Pi robot we built with it here. The Mini Driver is an Arduino that has just 8kb of memory (standard Arduinos have 32kb), but it's got some great features and a really nice price due to the joys of Chinese manufacturing. It's got a 1A voltage regulator, can drive 2 DC motors, and an on/off switch. The only downside is that you need to connect it to the Pi with a USB cable which isn't as neat.

Regards

Alan

[victagayun]

is it possible to power pi co-op thru 3v3?
I see some arduino using 16Mhz, they have a switch for 5V and 3v3

[Alan]

Hi victagayun,

Welcome to the forums. Sorry for the delayed reply.

The Atmega328 on the Pi Coop will happily run at 3.3V but I think running the Pi Coop at 3.3V will be hard as it is hardwired to the 5V pin on the Pi GPIO header. You may be able to run it at 3.3V if you cut the power trace and hard wire it to the 3.3V pin but it will be messy and you may damage your Pi.

If you'd like to proceed then you can find the schematic for the Pi Coop here.

Regards

Alan