SOLAR PV CONTROL SYSTEM.pdf
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have two independent sets of coils instead. They can be distinguished from unipolar<br />
steppers by measuring the resistance between the wires. You should find two pairs<br />
of wires with equal resistance. If you’ve got the leads of your meter connected to<br />
two wires that are not connected (i.e. not attached to the same coil), you should see<br />
infinite resistance (or no continuity).<br />
Feedback is not always required for control, but the use of an encoder or other<br />
position sensor can ensure accuracy when it is essential. The advantage of operating<br />
without feedback is that a closed loop control system is not required. Generally,<br />
stepper motors produce less than 1 horsepower (746 W) and are therefore<br />
frequently used in low-power position control applications.<br />
Like other motors, stepper motors require more power than a micro controller can<br />
give them, so a separate power supply is required. To control the stepper, voltage is<br />
applied to each of the coils in a specific sequence from the micro controller through<br />
a driver like the H-Bridge.<br />
Email: david.irungu@stu.kuct.ac.ke<br />
Figure 6: A unipolar stepper motor coils<br />
21<br />
2012
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