DIY : Versatile Shop Power Keycard System – Hackster’s Blog
There are many situations where you only want certain people to have access to power tools. A well-equipped hackerspace comes to mind, or perhaps your own garage with kids around, and this solidly-built and versatile card reader should be able to take anything that you throw at it, even if you’re running a commercial shop.
The device is powered by an Arduino Uno, using a USB shield to interface with its magstripe reader, and a datalogger to record who has turned the system on. A single user’s card is programmed in as the administrator, and more cards can be added by swiping it while holding the unit’s single button (which also doubles to turn the power off).
Interestingly, any card with a magnetic stripe can be read, so if your organization would like use recycled gift cards or something similar, this is certainly possible. You could even use a credit card as the ID method, though this isn’t necessarily recommended as the first 15 characters will be displayed on the device’s LCD screen.
As a backup, power can be turned on using a physical key as well, and it’s programmed to shut down at 5:15, securing things until workers come in the next morning.