We have conducted experiments with a maxon motor with an attached maxon encoder. A typical scenario of use will also include gears to reduce the rotation speed

When dealing with e.g. haptic devices it is important to count with motors that have a good time response. In technical terms this is called torque

Motors with a high torque factor demand a lot of current for starting the movement. The motor board can handle up to 25 VDC peaks (until 36 replacing one capacitor)

(in the picture, our experimental setting)

 

 

We have now seen two different ways of attacking the problem of controlling the motors. The first one allowed us to just turn the motor on or off, while thanks to the second one we saw how to change the speed of the motor.

But what happens with the direction of movement? If we plug 5 volts on one pin of a toy motor and ground (GND) to the other one we see how the motor moves in one direction, while if we switch pins, the motor will move in the other direction. None of the previously presented examples can be used to do this. Until recently the electronic circuit that could solve this case was having a complexity that made it very hard for interaction designers to study the use of motors at this level. Recently the appearance of the so-called integrated H-bridges has allowed us to approach the problem in a very easy way.

An H-bridge is an integrated circuit that takes:

a) a PWM signal as inputs that will drive the speed of the motor,

b) a bit to signalize the direction of the rotation, and

c) a connector for the power supply to feed the motor.

This is the solution we have chosen for the creation of our prototype, a board that can drive two DC motors simultaneously while controlling their speed through PWM and the direction through a digital pin. From wiring this means that it is possible to control the motors at a very basic level using the already mentioned commands: digitalWrite() and analogWrite().

The code to control motors becomes extremelly simple, here we show a couple of examples:

- Example 1: motor at connector-set A will increase its speed, and then decrease, while motor at connector-set B will also toggle direction

- Example 2: motor at connector-set A will toggle direction when pressing on-board button