MCU + Servo: Multiple voltages

Hi guys,

I wanted to control a SG90 servo with an Attiny85 and I came up with this, is this considered good practice? If not I would appreciate an explanation and an alternative solution.

Thanks in advance,
David.

I would just put a silicon diode from the battery + to the MCU +. That will drop 0.6V to 0.7V, keeping the supply voltage lower than the max supply voltage of 5.5V (for 5V Arduinos). Uneven discharge is not good.

It looks good but not reliable. As the batteries discharge you will probably lose control of the microprocessor depending on how it well the micro works at lower voltages. I would suggest using a SEPIC converter and use all 4 batteries in series to supply it which in turn supplies 5V to the Arduino. The efficiency of some of them is in the 90% range. This will keep your Arduino voltage stable well after the motor dies.

The MCU is an Attiny85, so it can operate well between 2.7 to 5.5 v

Take your power source and have two voltage regulators a 5V one for the processor and a 6V5 one for the servos.

like this?:

Yes, that is what I meant. If it is 5.38V with fully charged (new) batteries it will only go lower so, I think, 1 diode drop is fine. If you feel that 5.38V is too high, add another diode in series.

Do not use the physical pin1 (reset) for the servo control. Any other pin will work.

Thank you very much, I'll let you know if it works... :wink: