Toddler Video Remote for PC Video Player

Step 4 Modifying the Numerical Keypad

Next I took the keypad apart. Now, depending on the numpad, you will encounter different hardware inside, but all numpads should work according to the same principle.

They have a grid and each horizontal and each vertical line will connect to a pin on the USB chip.

In my case the grid itself was not a circuit board but conductive lines on two plastic sheets with an isolating sheet in between them. Although this is a very elegant design, it meant I couldn't directly solder onto the grid and had to trace the numpad circuit to figure out where to solder the wires.

Since I needed 5 buttons I had to trace the leads of the following buttons:

1, 2, 4, 5, 7 and 8.

Then I numbered the pins on the circuit boards and traced which numbers used which pins (look at the pictures for more clarification) and drew a small schematics for these buttons.

So to type the number 1, contacts 7 and 2 need to make contact, to type a 2, contacts 7 and 4 need to make contact with each other.

Then I soldered wires where the printed circuits was exposed. This was probably the hardest part, since these points were quite small. After soldering the 5 wires, I applied glue with my hot glue gun to prevent the contacts from breaking off the circuit board.

Then I hooked up the circuit board to the computer, opened notepad and verified if the numbers would come up if I connected the correct wires.