I am building GPS datalogger. It will consist of Arduino Pro Mini 3.3V, GPS module – GY-GPS6MV2 (GPS Ublox NEO-6M) (bypassing 3.3V regulator) or Skylab SKM53 (MT3329). Data will be written to SPI Flash W25Q64FVSIG and later read via USB with FT232RL FTDI 3.3V.
I am looking for a power supply solution having following criteria:
- powering with multiple standard rechargable NiMH 1.2V AA batteries
- effective power supply capable of higher current (my guess is 150mA but I am not 100% sure about this)
- automatic circuit cutoff on voltage drop below minimum recommended for the circuit and also for NiMH batteries to not to overdischarge and damage them
- notification of low battery power (eg. by bliking LED) before cutoff
So far I was trying to use DC-DC step-up voltage convertor with together 4 batteries – two pairs of serially connected baterries finally connected in parallel so they can provide doulbe current, but the circuit seems to require more current. Maybe I should probably consider rather some more powerful DC-DC step-down voltage convertor.
I've asked about automatic circuit cutoff and notification of low battery power already but I would appreciate to have a complete solution combined with all four requirements.
I will appreciate a solution to this complex yet common problem.
Best Answer
If you are using a microcontroller then you can implement some of what you're looking for just in firmware. Namely, the automatic low voltage cut-out is known as brown-out and is something you can set fuses for on the AVR chip itself in which a RESET event will be triggered. However, you might look into a latching circuit that could be switched off when a RESET occurs. See page 47 in the datasheet.
The blinking LED is about the simplest program you can write. Once low-voltage is detected, either through brown-out or ADC, drive an LED with PWM and a timer if you want it to blink. If you simply want an indicator then just drive the LED high and forget about it.