Powering the cam without a backup battery

We have noticed that the backup battery used to power the CMUcam is not very reliable, and dies out very quickly with our camera.
so we were wondering, is it possible to power the camera off of the Circuit Breaker Panel? that would be really usefull in this phase of developing, as we need the camera for the entire 4-8 hours we are here, and the main battery lasts that long (because all it is really powering is the RC).


(i ask becaus i dont want to fry the team’s camera…)

If your robot is still in bench-test mode, why not buy a little AC power supply and hook it up? That’s what we did. You can buy a multiple-voltage model from Radio Shack for less than $20.

ah thanks.
strange thing is that we were planning to make a tranformer0thingy to bridge between the cam and the breakers.
yah i guess that would be a good alternative.
thanks :slight_smile:

I seem to remember that last year I plugged it into an anlog input, which is +5v, and it worked fine. I haven’t tried it this year, but it might work. The +5v comes from the main battery, rather then the backup… you would still need the backup for the servo’s though

you definately need the backup batery or some 7.2 volt source connected to the RC for the camera to work those are really the only 2 options

My camera worked fine in LabVIEW by just using the 5v analog.

Hook a PWM cable from the camera power supply to an analog input.

That gives you 5VDC from the main battery.

Remember that transformers will only work with AC, not DC. :wink:


Theoretically, it should be possible to build a sort of voltage regulator that will plug into the breaker panel, and output a constant 7.2 volts, which you could plug into the backup battery jack on the RC. It would completely defeat the purpose of the backup battery, but for testing it would be much more convenient. Only problem is that I haven’t seen a 7.2v voltage regulator, but you might be able to get away with an 8-volt one and possibly a resistor or two.

Just use a LM317. It would be a good idea to use a diode-type splitter and tap power from the main battery and the backup battery, whichever is stronger.

Our team had this issue too. On the normal (not-FIRST) cmucam2 board, there are actually two +5v power inputs, one for the servos and one for the camera board itself. There’s also a jumper to set the servos to use external power, ie the second +5v input specifically for servos. I’m fairly sure that the first version of the board also has that jumper, but I can’t find the pins to hook the extra +5v for external servo power.

The servos work fine with only 5v in the normal power slot, but a little slower. (Our team connects the camera to digital in/out). I think the trade-off is worth it, though. For no irregular performance and no chance of draining the backup battery, you just take a bit of a hit in servo speed. This afternoon when I get to robotics though, I’m going to be poking around the FIRST cmucam2 to try and find where they moved the external servo power jumpers. If I find them, I’ll post here. That’d give us best of both worlds: assured battery life, and max servo speed.

Check out http://www.ifirobotics.com/docs/first-backup-charger.pdf

An online charger/supply circuit for the RC backup battery and hence all servos and the camera!

Lynn (D) - Team Voltage 386 Software