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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.

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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.

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A nice trick to get under voltage lockout (i.e. turn the system off when the battery voltage gets too low) is to buy a voltage regulator with an "enable" or "~shutdown" pin that has a precise threshold. Then you just form a divider off of your battery stack to set the threshold. You will want an enable pin that has some hysteresis for this. This is a feature of many Linear Technology voltage regulators.

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