Hi, this is my first post on this forum - I hope I’ve put it in the right place!
I am building a vehicle which will be driven by 6 Pololu 20.4:1 Metal Gearmotors High Power 12v (pololu.com/product/3203). They quote 300mA (max) free-run and 5.6A stall (!). The vehicle will have a Raspberry Pi (v3), probably other controller board(s).
How do I work out the battery requirements and which type would be most suitable? Is a single battery / power source the best option, or should I power the motors separately from the Raspberry Pi (and any other controller boards)?
Also, Pololu recommend keeping well within the stall current – how would I achieve that?
Hi,
It’s always highly recommended to isolate the power to the controller/logic (Raspberry Pi and motor controller in your case) and the motors. This way, the noise induced by the motors Back EMF on the power lines won’t affect the performances of the controller.
In this case, you can use separate power supplies for the Raspberry Pi and motors. A voltage regulator for the Raspberry Pi would also be a good solution of decoupling logic and motor voltage.
Before choosing the battery/power supply, first we suggest you to think about the motor controller you will be using. You will need a motor controller that can drive 6 of the 12V Pololu motors you have, providing enough current and can be controlled with a Raspberry Pi.
We suggest you to read through this blog post for more information on how to choose an appropriate motor controller for your project. Here is also a link to our Brushed DC Motor Controllerscategory.
The Sabertooth Dual 12A 6V-24V Regenerative Motor Driver could be a good option.
As for batteries, you can use an NiMh battery pack or a LiPo battery pack. For example, a 12.0V 2800mAh Rechargeable NiMh Battery Pack or a 11.1V, 4000mAh, 40C 3S LiPo Battery.
You can use a voltage regulator for the Raspberry Pi to isolate it from the motors voltage. You would need a voltage regulator that is capable of providing 5V 3Amps of current for the Raspberry Pi like this one.
Regards,
The Sabertooth Motor Driver looks good, but I am unsure what is needed in order to connect it to a Raspberry Pi. There seems to be an issue of voltage difference for the signal between the two - 3.3v from Raspberry Pi and Sabertooth needing 5v?)
I also see that there is another Sabertooth model with usb connection - robotshop.com/uk/sabertooth- … river.html - I’m not sure if that would make connecting it to a Raspberry Pi any easier?
Also, I have seen this controller robotshop.com/uk/roboclaw-2x … oller.html - that seems to be easier to connect to a Raspberry Pi as it handles inputs at 3.3v, is that right?
You are correct. Since the Sabertooth has 5V logic voltage level and the Raspberry Pi is 3.3V, you would need a Logic Voltage Converter between the two to convert 5V signals to 3.3V and vice-versa if you are using the Raspberry Pi GPIOs.
An easier way to use the Sabertooth with the Raspberry Pi is, as you mentioned, the USB connection. Here is the USBSabertooth Library to control a Sabertooth via USB in packet serial mode.
