Hobbies And Interests
Hardware
First purchase a keypad and an internal relay. The relay controls the actual lock. The keypad is typically a collection of buttons arranged in a matrix with 1, 2 and 3 on the top row, 4, 5 and 6 on the second row, 7, 8 and 9 on the third row, and 0 in the center at the bottom. These pads often also include a asterisk sign, a pound sign and the letters A, B, C and D. These may be purchased online or at brick-and-mortar hardware stores. Purchase a power source with a DC output, ranging between 8 volts and 30 volts, with a minimum of 200 milliamperes. You also need power-to-hold type electromagnetic lock with a breaking contact.
PICs
PIC stands for "peripheral interface controller." It is an all-purpose microcontroller that must be properly programmed before it can be used in homemade electric lock systems. PICs attach to the hardware using data cables that often come with the PIC itself. The details of connecting the PIC to the various pieces of hardware are very complex. Fortunately, widely available schematics are available, showing users exactly how to do this.
Source Codes
Programming the PIC requires a source code, which are readily available online. These include HEX files, which users may download with default values already entered. Significant variables include delay calibration, delay of the output pulse and the length of the code.
Operation
The lock operates by entering the correct code and pressing the pound sign, which functions as the "enter" button. The default code is typically 1 2 3 4. The code may be changed by entering the current code and pressing the asterisk sign, followed by the new code. If you are successful in making the change, the code change LED indicator light will light up. If you are unsuccessful, the original code is maintained.