# 4 Motors, 2 DRV8833. How much power and how to supply it?

Hello all. I’m hoping for some help from you incredibly smart people who know much more than myself about this stuff.

I am attempting to convert 4 roller shades in my family room into automated shades.

Here is what I’m using to try to accomplish this:
1 Microcontroller: Particle Photon Microcontroller
4 Motors: Gear Motor 3
2 Motor Drivers: DRV8833 Dual Motor Driver Carrier

I have 1 shade working as it should (up/down) but once I try to power 2 or more with my weak 5V adapter, there isn’t enough juice… I never expected 5V to power all 4 but now that I’m ready to power them all I’m stuck on how to move forward. I’ve tried reading up and educating myself but holy moly this stuff is confusing!

Do I get a 20 V power supply and run it through a 5V regulator and power both of the DRV8833’s that way? Do I need 2 separate 5V regulators? sending the output to the drivers? is 20 V too much? I feel like 20v / 4 motors is too simple and I’m missing something.

How would you all go about powering these guys? Thanks so much for any help you can give me. I appreciate it very much.

Pat

You cannot use a 20V power supply with those motors or that driver.
A 5V supply should work, but it should be able to deliver 4 times the stall current, or at least 3 amperes.

Sounds good. Thank you!

Hello, Pat.

Generally in electronics, when you power a device it needs to be supplied with a certain voltage, and the supply also needs to be able to provide the amount of current the device wants to draw. For a motor, the amount of current it will draw depends on the load on its output shaft. The largest amount of current a motor can draw will occur when the motor is stalled (i.e. the output shaft is not rotating). So, a good rule of thumb for picking out a useful power supply for applications using motors is to find a supply that can handle at least the full stall current of each of the motors in your application.

Also keep in mind that the amount of current drawn from a motor varies approximately linearly with the voltage of your power supply. For example, the GM3 motor has a stall current of 733mA at 6V. But at 5V, the stall current will actually be closer to about 611mA (5/6*733). So, multiplying that number by the number of motors you want to use will give you a good value to use for your power supply, which should be about 3A like Jim mentioned.

-Jon

Thank you Jon! I appreciate it