[Part 1: Introduction] [Part 2: Keypads] A whole month has passed since I posted my Digital Lock Pick Introduction, and I am pleased to report that it is going rather well. I have successfully interfaced an Arduino with an off-the-shelf keypad and managed to turn off the alarm without physically pressing any buttons. The image below shows the first prototype. So then, Keypads. I’ve based all of my theory and design around the basic structure of the typical home electronics keypad, but that’s not as crazy as it sounds. In doing some digging, I’ve found that most keypads follow the same basic structure, and work in basically the same way. *Please note that all the images below illustrate theory work that I had done before I looked at a real keypad. In testing, I have found that, contrary to what I read, it is actually the Rows that are high, and not the columns. Regardless, the basic structure and plan of attack are more or less unaffected. (It took ages to make all the images below, and I can’t be bothered to do them again.) They use a column and row structure that allows you to have, for example 16 keys, but use only 8 pins on the controller. The following images show a not-completely-accurate-but-accurate-enough-for-illustrative-purposes representation of a matrix keypad. In order for the controller to recognise which of the 16 buttons the user has pressed, we must do some deduction. In this image we can see that all the columns are high and all the rows are low. *See note above. When we press the button for digit 1, we connect column 1 to row 1, and this equals 1. Likewise, when we press the button for digit 4, we connect column 1 to row 2, and this equals 4. Continuing, connecting column 3 to row 1 gives us 3. And Connecting column 4 to row 4 gives us D. This seems to be the basic structure behind most keypads, and I can see why, it works quite efficiently. The complicated part comes when we try to press these buttons electronically, and not use 16 pins in the process. There are multiple ways to do this, I have come up with two myself, but the way I am going to show you is my favourite, well, currently anyway. We’re going to use AND gates,...