More power to the servos?

#1

I maxed the power value to 255 in the wifi car sample - but it is still significantly slower than the the same car design using the nxt (everything else the same)

Any suggestions on getting more power to the servos so I can chug along a little faster?

Power is currently coming from a usb wall adapter rated at 5.2v

Ken

#2

If you are running motors, it is a requirement that you power the BrickPi with 9v (minimum of about 7.2v), regardless of whether you are providing the RPi with 5v through USB.

Although the motors do still run when the RPi/BrickPi is only powered by USB, it is potentially abusive to the motor drivers (SN754410 H-Bridges). I personally haven’t had any damage done to mine while testing, but it’s outside of what the drivers are designed for.

Properly powering the RPi/BrickPi will make the motors much faster.

#3

kfuhr, can you add a 9V supply to the BrickPi?

#4

I plugged the AA battery pack into the Brick Pi and left the USB power plugged into the raspberry - that made a difference. The Servos are moving much faster. Will have to play around with the batteries (I put new ones in, but they don’t seem to be providing enough power - could not even get the wifi dongle to work with battery power alone).

I am using alkaline 1.5v AA batteries. Is it better to use lithium batteries, or just get a larger battery pack - go for 8 instead of the 6 that came with the brickPi?

I have seen a few mentions on measuring the power output - where are you measuring it - on the battery pack or somewhere on the BrickPi? And will my volt meter i use for the house wiring do or are you using another tool?

Regards,

Ken

#5

Ken,
It sounds like you have a heavy draw. Yes, this can lower the voltage and make the motors slower. So increasing the power available (and voltage) with an 8-pack might be a good idea.

If you want to measure the voltage, the best place to do it is on the terminals of the battery pack. I think. Matt might have a better idea. You can measure it unconnected, and then measure it while running, this will give you a better idea of how much power your RPi and BrickPi are drawing from the batteries.

Best,

John