Bluetooth Energy Saving with HC05

Projects General Guidance
1

Hello,

I am working in a microcontroller operated cattle autofeeder, with solar energy.

Everything work nice.

I want to save the 26 mA that my HC05 drains.

The BT is used only two minutes at startup routine. So it listens a cell phone connection to read the new work parameters, which are immediately written to EEPROM.

If BT comms is not received, the system has a timeout routine and default to read the last know params from the EEPROM.

I have different options to disconnect HC05.

  1. To feed it from a PIN, that UNO datasheet says can provide 40 mA, then when startup routine finishes turn off power to HC05.

  2. To use an external relay (or optocoupler) to disconnect, and drain less current from PIN. An optocoupler driving a little MOSFET, with VCC of HC05 connected to +5Volt and ground connected to MOSFET drain should work, and is electrically isolated cheap solution.

  3. To use some sort of software handled "sleep mode"

Any advice ?

Thanks a lot,
Horacio

2

I don't think there is any "sort of software handled "sleep mode"" other than that which you have already proposed in item 1.

3

Software can't turn off the 3.3volt regulator of the HC-05.
Switching VCC of the HC-05 with a PNP transistor seems the logical answer.
Emitter to 5volt, collector to HC-05 VCC, base via a ~470 ohm resistor to an output pin.
Writing a HIGH to the pin turns the HC-05 off (and also won't use any base current).
Leo..

4

Hello,

This is solved with a BC556 !

Thanks for the answers,
Horacio