Hello. I have a wall plug that has a barrel plug on the end that is the right size for the BrickPi. I looked at the back of it and it says that the output is 12V 1.5A. Would it be safe to run 4 motors and no sensors off the BrickPi this way? If not, can you recommend a wall power supply for me? Thanks.
It all depends on how much your use your motors. Your batteries can supply a much greater peak amperage than 1.5A. Each motor can take a peak supply of 2A. So running 4 motors at full blast is going to to require up to 8 amps.
Take a look at this site: http://www.philohome.com/motors/motorcomp.htm
12V and 1.5A is largely enough to power the 3 motors in normal operation. Personally I use a 9V, 500 mA power supply for the brickpi board in addition to USB adapter for the raspberry.
2A is the stalled current consumption and can be sustained for only a few seconds.
Indeed, it’s a stalled motor consumption, very good! When you draw this kind of amperage from a 500 mA power supply, the voltage will drop and turn the Raspberry Pi off.
You’re right John. If I use only my little 500 mA power supply, when I power too many motors, the voltage drop and my raspberry reboot.
This cause no damage to the brickpi or raspberry, it’s just annoying. To avoid this, I power also the raspberry this a simple USB adapter as recommended here: http://www.dexterindustries.com/BrickPi/getting-started/power-up-the-brickpi/
So, it is why I think that KingRandomGui can try is 1.5A power supply before buying a new one. Take care of the polarity !!!
If the raspberry reboot, just power also the raspberry with a USB adapter.
According to this site: http://www.philohome.com/batteries/bat.htm, NXT brick does have a 1.85A nominal resettable fuse on its power input.
It is why I’m surprised that you recommend a 12V 8A power supply.
John, can you guarantee that with such a power supply, in case of stalled of the 4 motors, the brickpi board and the lego motors can sustain this current without damage ?
That should work pretty well, if you use a USB adapter as well. There’s a fuse on the BrickPi as well, but it is not inline with the motors. And, like most fuses, it can survive a short peak of power.