Stepper Motor Controller

This circuit leads palmorefmata coils,, engine. Each coil is driven by a transistor type Darlington. Darlington Transistors internally comprise two transistors connected in series. The `hfe` Darlington is equal to the multiplication of `hfe` of both its internal transistor. The Darlington 2SD1209K used in the circuit is `hfe` greater than 4000. Because the ratio of power input / output is high, the rising and descending front of the driving pulse can be steep. To protect the transistor from voltage spikes placed in parallel with each coil and a diode reverse polarized. When the transistor switches from a standard conductivity in the coil of the stepper motor displays current flow which creates a high voltage, this trend means eliminated the protective diode.
Stepper Motor Controller - schematic

Speed ??control circuit With this circuit is to control the speed of the engine. When the situation at the foot RB7 be logical 1 (High), the transistor TR1 conducts. In this case, the capacitor C1 will discharge means of the transistor TR1, and the tendency to extremes becomes 0 V. When the situation at the foot RB7 be logical 0 (Low), the transistor stops conducts, current passes through the potentiometer VR1, the resistance R4 and charge the capacitor C1. For more information on the charging and discharging click here: "Circuit R / C". The logical 1 (High), node R4 and C1, is detected by the foot RB5, as soon as the situation in RB7 be logical 0 (Low). The lower the resistance of potentiometer VR1 another so diminished and the charging time of capacitor C1. The engine speed diminishes as the resistance of VR1 increases, so the engine speed is inversely proportional to the resistance value of potentiometer VR1. Circuit starting rotation or pause This circuit determines if the motor will rotate counterclockwise or clockwise if it stops. A switch button and a Pull-up resistor connected to the foot RB5. The door RB has the ability to use the internal chip resistors Pull-up, but because the foot RB5 detect voltage that is logical 1 (High), it was considered safer to use an external resistor Pull-up. Timing Circuit For the timing of the processor used a ceramic filter (Resonator) or 4-MHz crystal...

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