Yaskawa Industrial Servo Motor 100W 0.318N.m 3000RPM AC Electric Servo Motor SGM-01AWJ16B

Four NPN power transistors, four resistors, and a handful of diodes are all the translator circuits described in the last section need to provide driving power. (You can also use this scheme to increase the driving power of the UCN5804, detailed earlier). The schematic for the circuit is shown in Fig. 19.10 (refer to the parts list in Table 19.4). Note that you can substitute the bipolar transistors and resistors with power MOSFETs. See Chapter 17, "Choosing the Right Motor for the Job," for more information on using power MOSFETs. You can use just about any NPN power transistor that will handle the motor. The TIP31 is a good choice for applications that require up to one amp of current. Use the 2N3055 for heavier-duty motors. Mount the drive transistors on a suitable heat sink.

You must insert a bias resistor in series between the outputs of the translation circuit and the base of the transistors. Values between about 1K and 3K should work with most motors and most transistors. Experiment until you find the value that works without causing the flip-flop chips to overheat. You can also apply Ohm's law, figuring in the current draw of the motor and the gain of the transistor, to accurately find the correct value of the resistor. If this is new to you, see Appendix A, "Further Reading," for a list of books on electronic design and theory.