jkling
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Joined: Sat Jul 13, 2019 4:32 pm

Power small motor (directly) from PI 5V

Sat Jul 13, 2019 4:47 pm

Hey Guys,

I want to control a small RC Car (Wltoys L939 https://www.google.com/search?q=wltoys+ ... e&ie=UTF-8) with a Raspberry Pi Zero W. The raspberry pi is currently powered with a 1200 mAh LiPo using the GIPO pins and a Powerboost 1000C (https://learn.adafruit.com/adafruit-pow ... t/overview) in between. The RC car had a 120 mAh LiPo build in, so the battery should deliver enough power to control the motor. Since by PI is already battery powered, I don't want to use any other power source other than the 1200 mAh Lipo (3,7V) to power the Pi AND the car. What's the best way to do it?

After some random searches I am still not sure whats the best approach or even how to do it. I want to power this motor ( https://www.wl-toys.com/Wltoys-L939-Pa ... 0190.html ). Should I use a H Bridge Driver (something like this: https://www.ebay.de/itm/L9110S-H-bridge ... 2453254223) or a Motor Shield for the PI? Or just a L293D? All the motor examples with the Pi or Arduino power much higher voltage motors with external, high volatge power sources.

Thanks for your suggestions.

pcmanbob
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Re: Power small motor (directly) from PI 5V

Sat Jul 13, 2019 7:24 pm

Hi.

Powering the pi and the motor from the same battery may not work because the motor is going to cause sudden drops in battery voltage when starting or under heavy loads, which could cause voltage dips which you pi might not stand, and could cause it to reboot.

As for the best motor driver its difficult to give advice as there are no details of the motor current drawn in any of your links, so you are going to have to do you own tests to find the motor current before you can decide on the best motor driver option.
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LTolledo
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Re: Power small motor (directly) from PI 5V

Sun Jul 14, 2019 6:01 am

As I have answered this on similar topics

you can power the motor directly from RPi's 5v

one speed, one direction, and one time only!

after that your RPi is K.I.A or R.i.P.

motor driver boards are best used for these types of applications, to protect your RPi "investment"
if the motor you have is a brushed DC motor, the you need a driver board for a brushed DC motor... the L293D or DRV 8870 are good candidates
the dual L9110S boards are also a compact one to control two motors

just check the maximum rated current of the motor and match the controller board respectively,
my rule of thumb is getting a motor controller usually is: (note others may have different methods from mine)

[motor max current x 1.3 (or 1.5)] < [motor controller rated current]

also in most RCs (I own several) the power for the controller circuit is usually separated from the motor driver power.
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Imperf3kt
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Re: Power small motor (directly) from PI 5V

Sun Jul 14, 2019 10:20 pm

LTolledo wrote:
Sun Jul 14, 2019 6:01 am
As I have answered this on similar topics

you can power the motor directly from RPi's 5v

one speed, one direction, and one time only!

after that your RPi is K.I.A or R.i.P.
What kills the Pi?
As far as I see, you are merely connecting a motor ditectly to a current source. If the motor draws too much, the voltage drops and eventually the Pi reboots due to low power.

It's a different story if you try to connect it to a GPIO pin or if you turn the motor off.
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IOTON
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Re: Power small motor (directly) from PI 5V

Mon Jul 15, 2019 5:09 am

pcmanbob wrote:
Sat Jul 13, 2019 7:24 pm
Hi.

Powering the pi and the motor from the same battery may not work because the motor is going to cause sudden drops in battery voltage when starting or under heavy loads, which could cause voltage dips which you pi might not stand, and could cause it to reboot.
In theory, pi zero must work with only 2.5 volt power supply.
I don't think voltage drops will cause a problem.

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