19.1 Choppers and Microstepping
In Chapter 18 we discussed circuits and programs for bipolar motors that operate with a constant voltage through the coils. In this chapter we discuss controls in which the current through the coils is held approximately constant, instead of the voltage. One type of constant-current design is referred to as a “chopper” circuit. In the chopper the current in each winding is held approximately constant by varying the voltage. In operation, a high voltage is initially applied to each winding, causing the current to rise quickly. When the current reaches a predetermined limit, the voltage is “chopped” off and the current drops. The cycle concludes when a pre-determined low current ...
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