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Re: Battery powered raspberry pi
I think I should design a small lithium battery pack of something like 180mAh to be COTS legal. Maybe have an MCU to automatically switch to battery and send a signal to the Pi to shut down before a timeout (hard shutdown).
What do ya guys think about some system to get legal in COTS, to allow a small battery? Also, if I were to do something like this, what should be the communication? Also, note that I am aiming not for the RPI, but for devices like the oDroid, with a higher consumption. I think you'd be better off doing driver station vision than using a Pi!
So, I thought of a small LiPo Charger circuit, EXCEEDING safety standards, to charge the battery off the robot battery, or a computer mini-USB. That would go into a boost converter rated for 5V out, because a 1s battery means 3v7. Then, it powers an MCU, being the power manager, to tell the Pi to kill all processes and shut down. Then, the Pi, powered by a MOSFET will be disconnected by the MCU. Then the MCU will go into sleep/watchdog mode, waiting for the battery power to be regained, or the power switch to be turned off.
I think that if I can make something like this in the Christmas Break and get it FRC legal, probably by 2016, not before 2015, it could be a game-changer for one of the teams who wants vision tracking!
About powering the Pi/other SoC from the robot battery:
There are the power pins on the header of the Pi. There is an FRC-legal boost-buck converter with a 5-volt output. Please let me know if you would like a picture of it on Wednesday. That should do the work, much greater than what it is required because I think it is rated for either 3 or 5 Amps continuous! However, I do not know if that provides very tightly regulated power since it is a buck-boost converter, so I would put something like a 15V, 100uF electrolytic capacitor in series with the Pi to eat up the voltage sparks that could kill the Pi! That should get you rocking and rolling with powering the Pi at competitions. Other than that, has anyone tried a supercapacitor (one meant to hold a large charge and not release it instantly) to power a part of the Pi like the CPU/RAM/other important thing? This is the type of capacitor used in RTCs so they don't forget the time.
I think it is time for a modded Pi that has the ability to sleep, by turning off the processor and everything except the RAM. The RAM would be suspended to make sure it's contents stay where they are.
Also, I think there may be some ways detect when the match is over to automatically shut down the Pi. I think that may be the easiest option!
Last edited by yash101 : 09-12-2013 at 18:35.
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