Chapter 4 - Exercise 20 - Number Pad

Apologies for the delay in posting... I've got quite a bit of work piled up from a trip out of town and am trying to catch up. Exercise 20 is going to be a multi-part project as I've not been able to find a DPDT dual coil relay locally...

In preparation for the exercise, I purchased an IDE cable (for a hard drive) for $6.00 and cut it so it has 17 wires (14 for the keypad and 3 extra in case I mess up soldering or cut a wire accidentally).



This is tedious - you have to be very careful with the cable because it's so easy to rip a single wire.
I used an X-acto knife to cut each wire apart (except for the 3 spare wires).
I stripped off 1/4" from each end - one end will connect to the 14 solder spots on the keypad... the other end is where I'll solder solid core wire (maybe 1" or 2" strands) so I can use it with the breadboard. As it is, the wire is simply too thin to insert into a breadboard. Once I pick my code, I can save some wire by joining 3 or 4 of the keys not used in the code and then soldering them to a single solid core wire. I don't think I'll be able to solder all 11 unused wires (14 - 3 for code) to a single strand.

I also don't have a spare computer to cut apart and mount this thing - I have 2 laptops and I don't think my wife will agree to let me experiment with her desktop computer.

Now to go find a DPDT dual coil relay...