Hardware Reference
In-Depth Information
Project Schematic
Figure
7-7
shows the schematic for the bipolar motor driver. If you are using a purchased
PCB, the only important details are the connections to it. The schematic, however, helps
us visualize all the separate components involved.
Figure 7-7.
L298 schematic
In this circuit, the enable inputs A and B have been tied together so that only GPIO
17 needs to be allocated to drive it.
Junk-Box Motors
If you've been an electronics hobbyist for a while, you likely have a bipolar motor in your
junk box. If not, salvage one from an old 3.5-inch floppy disk. Its seek motor will likely be
a bipolar stepper. Another source of stepper motors is an old flat-top scanner.
Bipolar motors are easier to figure out than unipolar motors. There are only four
wires, and they operate in pairs. To identify the pairs, simply take resistance readings.
A low reading will identify one pair of wires. Once that pair is identified, the remaining
two wires should be the second pair and read similarly. Make sure there is no connection
between the windings. They should be electrically isolated from each other.
