Powering attiny85 as well as h-bridge motor and logic off of one power source.


I know that manufactured hbridges have separate inputs for logic power and motor power because motors typically require more power; however, I am using a low voltage motor and would really like to run the whole thing off of one power source. I have done this in the past using an adafruit trinket and running the h-bridge logic off of the 3v output on the trinket while the motor and trinket run on the same battery. (see first pic). Is it possible to somehow use resistors/voltage splitters to run everything off of one battery if I just use the attiny85 on a breadboard (see second pic).

The hbridge I plan to use is Pololu - DRV8838 Single Brushed DC Motor Driver Carrier which is designed to run motors at low power. This is not the h-bridge in the diagram.

The motor comes in a kit that has it running off of 1.5 volts.


is it possible to somehow use resistors/voltage splitters to run everything off of one battery

You need a voltage regulator. Typically, the motor has a higher voltage rating (i.e. 12V) and you regulate-down the voltage to the microprocessor. But, with a 1.5V motor you've got the opposite situation. (Or of course, you can have two or more regulators for various voltages.)

Resistors won't work because the "load" (motor or microprocessor circuit, etc.) is not a constant resistance... When you change one of the resistors in a [u]voltage divider[/u] the output voltage changes. i.e. When a motor first turns-on, or if you put a load on the motor it's effective resistance drops and it draws more current. If an LED comes on, your microprocessor circuit draws more current, etc.

I am planning something similar using an Attiny84 and a Pololu DRV8833 driver powered from a 2s LiPo.

I plan to use a 3.3v regulator (LD33, I think) to produce the correct voltage for the Attiny. I am also using an nRF24L01+ which requires 3.3v.


Thank you both for your responses. Due to the additional cost of attiny85 programmer and the voltage regulator, I am going to opt to just purchase the trinket.