CHAPTER 17 ■ DC MOTORSSelecting a Battery for the Simple DC Motor Circuit
You must exercise a little care when selecting the battery. Most toy motors are designed for operation at 3 V.
Although you can connect a 3 V motor to a 9 V battery for a dozen seconds or so, the motor starts heating up
(you can feel it). Give the motor a minute to cool off between 9 V bursts. There are plenty of rugged DC brush
motors designed to continuously accept 6 V, 12 V, 24 V, and higher.
If you only have a 9 V battery, that will do for this experiment. If possible, check with the voltage setting
on your multimeter to select a 9 V battery that has run down a bit in voltage. Even better, get two AA-size
cells and a holder (see Figure 17-12); they’ll provide the appropriate 3 V.
Building the Simple DC Motor Circuit
The schematic for the simple DC motor circuit is quite simple, indeed (see Figure 17-13). B1 is 3 V of battery
power and M1 is a DC brush motor. Note that the schematic symbol for a DC motor is an underlined letter
‘M’ within a circle.
Figure 17-12. Two AA-size cells and holder
Figure 17-13. Schematic of simple DC motor circuit