The servo’s shaft (which is also the potentiometer shaft) has mechanical stops to prevent it from rotating too much. From the bottom, you can access the servo’s circuit board. From the top you can pull off all the gears (note which ones go where). You can use a small blade screwdriver or similar thin wedge to separate the pieces. These servos have a case made of three pieces of plastic, press-fit together.
By removing the pot from this loop and inserting two fixed resistors of equal value, the servo will now drive the motor continuously either forward or reverse, with a speed proportional to how far away the commanded angle is from the mid-point. The control electronics compare the commanded angle and compare it to the angle read by the potentiometer, and then proportionally controls the motor’s speed depending on how close the shaft’s position is to where the servo is being instructed. Physically, servos contain a DC motor with a gear train, a potentiometer connected to the output shaft, and control electronics that reads the position of the shaft with the pot. Servos have a pulse input that specifies what angle the servo should be positioned at.
#Hacked servo motor arduino how to#
Here’s how to modify one of those servos to make it into a tiny little gearmotor. The ones I use here are the Hextronic HXT500 available for $3.49 each. I’ve been getting cheap servo motors from Hobby City, and they have several super-tiny servos for less than $4. You can even buy a nice continuous servo made by Parallax. Modding servos for continuous rotation is not a new hack. It turns out cheap servos can be made into continuous rotation gearmotors. I want a really cheap, almost throw-away, source of gearmotors.
Most gearmotors are pretty expensive though. Gearmotors are motors with a gearbox that slows down the high speed of the motor and produces higher torque. DC motors by themselves spin too fast and have low torque.
I’ve been exploring various types of gearmotors.
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