Motor choices

At the centre of the robot’s performance is the motors and motor drivers.  We’ve tried many options over the years: old drill motors (cheap and powerful, no position feedback), stepper motors (very controllable, heavy, expensive), brushed DC motors with gearboxes and encoders (fairly powerful, fairly expensive, good position feedback).

We’ve considered (but not yet chosen) brushless DC motors (most powerful for their size, controllers very expensive).

This year (like last year) we went with brushed DC motors with gearbox and encoders.  Last year’s units came from China via ebay which caused us trouble when a gear cracked at the last moment and we were unable to get a replacement in time.  This year I decided that all our critical parts were going to come from suppliers in Europe, and be a brand name so that they could be easily purchased from multiple suppliers.

We went with Pololu gear motors – 25mm diameter units with gearboxes.  These motors come in a range of power/gearing options with the same form factor and we could buy them from both RobotShop and TME.  The motor drivers were the same as last year: 13A Cytron units from Robotshop.  These should be able to deliver twice as much current as the motors can handle.

Here’s the populated chassis.  Motor drivers are on the left, Pi + propeller + interconnect board are on the right.  Space for a LiPo battery is at the front.  And right at the bottom is a little 5V switch-mode power supply (as used in model aircraft) to power the logic boards.


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