Stepper motor
Stepper Motors
Stepper motors move a known interval for each pulse of power, making them handy devices for repeatable positioning. Generally they come in two flavours: bipolar and unipolar. The Darwin design uses bipolar motors,.
Bipolar Motors
These motors are the strongest type of stepper motor. You identify them by counting the leads - there should be four or eight. They are also the type of motors we are using in the RepRap Project's Darwin design. They have two coils inside, and stepping the motor round is achived by energising the coils and changing the direction of the current within those coils. This requires more complex electronics than a unipolar motor, so we use a special driver chip to take care of all that for us. Some designs (the eight-wire ones) split each coil in the middle so you can wire the motor either as bipolar (short the middles) or unipolar (short the middles and treat the link as the centre tap - see below).
Worldwide Suppliers
ST5709S1208-B stepper motor from Farnell (supplied by Nanotec Gmbh). This is the standard RepRap stepper motor (it is an eight-wire one). It has 400 steps to one revolution (0.9o per step).
Your RepRap machine will need three of these stepper motors. Chop the four white + coloured-stripe wires short - about 50 mm, strip them, and twist and solder the read-and-white one to the black-and-white one, and the yellow-and-white one to the green-and-white one. Put heat-shrink sleve over the connections to insulate them.
Then solder a 4-way 2.54mm-pitch (0.1") socket onto the other four plain coloured wires. The pin numbers are:
Pin | Colour | |
1 | Red | |
2 | Black | |
3 | Green | |
4 | Yellow |
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