Its a relatively simple question; How much power does the FRC controller (the one on the robot, I hope I have the right name…) draw from the backup battery?
Also, the FRC board has the ability to output power, and according to the rules of this year, the only legal way to use a backup battey is through the FRC controller…would it also be possible to use this output power to power the fisher-price motors? or, for that matter, any of the motors in the kit?
I am unsure of this. I know that after a few minutes the RC goes dead if running on backup, but I’m not sure if that’s because of a timer or the battery going dead.
The backup battery will not power any motors…ever. Your main battery is the only power source for motors, and motors must be powered by Victors or Spikes.
Good luck
JBot
From the 2006 controller docs (the 2007 kit still uses the 2006 controller):
The +12V and GND connectors on the Robot Controller are intended to accept power from a +12V
battery. The current draw for the Robot Controller is typically between 0.75A to 1.5A. The maximum
voltage allowable is +15.0V. Exceeding the +15.0V limit may damage internal voltage regulators and
will void the warranty. The minimum required voltage to maintain radio link is +7.0V.
On the controller board website:
The total combined current supplied from all 16 Analog and 18 Digital +5V Power header pins is 1 Amp. The 1 Amp max can come from a single +5V Power pin.
So basically the controller board probably won’t be able to power any drive or arm motor without some external power.
The backup battery (or at least last year’s, I’m not sure if the new one is different other than being yellow) was 700mAh I believe, which would power the controller anywhere from less than half an hour to less than an hour, assuming “typical” power usage. With such little power, I doubt it would be useful for powering motors even if you were allowed to. (You’re only allowed to use it as a backup battery, and as far as I know there’s no way to channel off power from it when the main battery is connected and charged.)
From what i know about the back-up battery is that it is strictly a back up as it name states it to be. The only motors it can power are the servo motors on the camera system. Everything else gets powered form the main battery through victors or spikes.
You can only drive motors (other than servos) using Spikes or Victors.
Why not just limit the speed using the Victor?
The specification above (0.75 amp to 1.5 amp) is nearly correct. The five volt regulator built in is designed for a max of 1.5 amps but the RC by itself draws up to 0.75 amp. The RC is designed to draw current from the backup battery when the main battery falls below 8 volts for more than a few seconds. During this time, the backup battery supplies current to the RC and radio modem to maintain communications and the backup also supplies current to servos connected to the PWM outputs of the RC. When using the CMUCAM, the backup is supplying current to it as well.
The backup battery cannot be used to power any motors on the robot other than servos when connected the serov is connected to the RC.
As a final note, all motor control is disabled by the event controller and so all motor control must be powered by the main battery through the main circuit breaker and must controlled by either Spikes or Victors connected to the RC per the Robot section of the manual and the electrical drawing.
The backup battery powers the camera, so if you have the camera this year you need a good battery in the robot to have you camera working well