Computerized Etch a Sketch

Step 12 Wire up your breadboard

Wire up the L293D on the breadboard according to the schematic. Don't forget the 10K pull-down resistors--this is one of the handiest things I learned when dealing with L293 chips--the inputs have a tendency to 'float' high, and turn on even if your micro is asking it to stay low. The pull-down resistors keep this from happening.

If you're using an stk500, throw your mega48 into the green socket, and plug one of the 10-pin connectors into the portB header. Don't forget to wire the 5V and (more importantly) circuit grounds together. If you want to put the mega48 on the breadboard, that's fine, too. If I'm building a temporary circuit, I just like to use the stk so I don't have to wire up as much.

You'll also notice on the schematic that there are two power supplies, VCC and VDD. Vcc is the 5V supply that powers the atmega and the logic side of the L293 chip. There's another side of the L293 chip that deals with the power that actually goes to the motors, and it's a very good idea for these two power supplies to be separate. I used a pack of 4C cells to power the motors, and that lasted for three weeks of playing off and on with this thing.

Comments

[trumpkin]

where is the ground from the motor battery supposed to go?

[trumpkin]

would the pullup resistors be a different value if you used deifferent motors?

[trumpkin]

so pin 1, 16, and 9 are all connected to 5 volts?

[prank]

yup

[stasterisk]

4 C-cells to get 6V, or for life, liberty and the pursuit of amps?

[prank]

wey-all, them amps don't hurt much, but dem L-293s need at least 6V on the power side to work well. Ja coulda useda four AAs, but dey'd just do dead fasta