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Step 5Add the 2nd layer + column resistors
To isolate the leads of the LEDs, cut a smaller piece of perboard to go over the connections you have already made. Do not make it any bigger than necessary.
Again, match up the pin connectors of the microprocessor with your matrix. Some microcomputer boards have an extra space between pins 7 and 8 and you must allow for that.
Join all the negative (cathode) leads of the LEDs vertically as shown below. Install the 6 resistors to match up with pin 2 (at the end) of the microprocessor with column 6. The other connections are pin 3, col 5; pin 4 col 4; pin 5 col 3; pin 6 col 2 and pin 7 col 1.
After you verified all your connections and trimmed off all the ends, your LMP is complete!
A quick test is to connect a 3 to 6volt source (like 3 or 4 AA batteries) and touch the + to a ROW (pins 8-12) and the - to a COLUMN (pins 2-7), ONE and only one LED should light up.
A word on the choice of resistor. The value (390-ohm) selected is for 8mA to go through the LEDs. This may seem low but the efficiency of the driving program make it unnecessary to use higher power. If absolutely needed, the resistor can be as low as 220-ohms.
Now, if everything looks OK, plug in your LMP, making sure (again) that pins 2 - 12 match up with the sockets on the Arduino. Then you can paste the following program in and see your efforts light up!
Continued in Part 2
Again, match up the pin connectors of the microprocessor with your matrix. Some microcomputer boards have an extra space between pins 7 and 8 and you must allow for that.
Join all the negative (cathode) leads of the LEDs vertically as shown below. Install the 6 resistors to match up with pin 2 (at the end) of the microprocessor with column 6. The other connections are pin 3, col 5; pin 4 col 4; pin 5 col 3; pin 6 col 2 and pin 7 col 1.
After you verified all your connections and trimmed off all the ends, your LMP is complete!
A quick test is to connect a 3 to 6volt source (like 3 or 4 AA batteries) and touch the + to a ROW (pins 8-12) and the - to a COLUMN (pins 2-7), ONE and only one LED should light up.
A word on the choice of resistor. The value (390-ohm) selected is for 8mA to go through the LEDs. This may seem low but the efficiency of the driving program make it unnecessary to use higher power. If absolutely needed, the resistor can be as low as 220-ohms.
Now, if everything looks OK, plug in your LMP, making sure (again) that pins 2 - 12 match up with the sockets on the Arduino. Then you can paste the following program in and see your efforts light up!
Continued in Part 2
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