Controlling Motors Manually
Part I
One can control a motor by simply turning it on and off. Reversing a motor requires that you reverse the current. When we have two motors this becomes troublesome. (You can learn how to use switches to control the motors by clicking here: Motor Reversal)
To solve this problem more easily, we will use the L293 is an H bridge controller circuit instead of manual switches. You can learn more about H bridges at: http://www.robotplatform.com/howto/L293/motor_driver_1.html. For our purposes, we will simply summarize this chip as the interface between the Arduino mircoprocessor we will use a bit later and our motors. (We will explain more of this later).
We will be using a breadboard in our next experiments. A breadboard is a way to connect wires in a temporary way to test various circuits. There are two "Rails" on the edge of this board, one with a blue line and another with a red line. These two rails are used to supply the battery voltage to whatever circuits we might want to build.All of the pin holes next to the blue line are internally connected. All of the pin holes on the red row are internally connected. The red row on the top is not connected to the red row on the bottom, however. Neither is the blue row on the top connected to the blue row on the bottom.
The rest of the board is a little more complicated. The center rows are labeled 1-30 and a through j. The way these work, for example, is that in row 1, a through e are connected together. In that same row, f through j are connected together. See the diagram below:
Find your breadboard already fitted with the L293 chip. Note it has 16 pins and there is a notch on one end. There are also 4 push button switches fixed to the board.
The L293 chip should have a small notch facing to the left. If this is not the case, the chip will need to be removed and turned around.
L293 H Bridge. Notch on left. Pin count starts on the left front, 1-8 and then curls around the other side 9-16. See the pin-out diagram below
Pin-out diagram for the IC
Follow the wiring diagram below and confirm each step with the directions that follows. Use connector wire that is tinned. Use the appropriate colors to track your connections.
A) Connect BLUE rails on board with BLUE wire
B) Connect RED rails on board with RED wire
C) Connect pins 1, 8,9, 16 of L293 chip to RED—Positive
D) Connect pins 4, 5, 12, 13 of L293 chip to BLUE—Negative
E) Connect pins 3, 6 to MOTOR 1 (Shown as grey)
F) Connect pins 11, 14 to MOTOR 2 (shown as grey)
G) Connect a RED (positive) wire to each push button switch
Observe carefully to double check the pin numbers and the connections.
PART 2
To complete the circuit, Connect pins 2,15 and 7,10 of the L293 chip— to the other connection of the push button switch (YELLOW)
When complete, your board should look like the photo below
Part 3
Once the wiring is complete, the battery supply (6 Volts) can be attached to the breadboard. Connect the positive to the red rail and negative to the blue rail. Test your H bridge by pressing one button at a time. Each motor should go back and forward.
Here is what your system should look like:
You are ready now to control the board with a microprocessor! Next Step, connect the microprocessor!