Stephen B. Hirsch had some great security ideas back in 1980 to solve an issues with push button locks:
It’s very easy to “shoulder surf” to get the key positions pushed, by position or by sight
Commonly used buttons wear more than unused numbers, leading to knowing which numbers compose a combination
Hirsch developed a lock that solved most problems common with previous push button locks:
Numbers are not displayed until the lock is being used
A limited field of view of each number using optics
The numbers on the keypad are “scrambled”, they appear in different positions with each activation.
It takes only a limited number of entries before it accepts no more attempts or sets off an alarm
There is nice audio feedback on start, for each button press and for error notification
You start the combination entry process by pressing the Start button in the lower left. A scramble animation appears on the 10 positions shown in the picture below. Then the user enters a set combination of digits and presses the lower right blank key. If the combination is correct, the controller unlocks access and logs the access in a database. The use can be coupled with needing a card swipe card.
What were these things used for?
Both private and government installations used these types of control systems. This company describes using it in a nuclear facility for example. Given the cost, the facility would require a substantial security budget for installation and assess database maintenance.
You can find the keypads on eBay, but for a full system you need the 1, 2, or 8 position control units and programming software which is expensive. Hirsch systems are still sold commercially on security websites.
These devices are a lot less common now as they do not generally meet current federal standards for some types of use.
If you want to simulate this on your own device, you can look to use an LCD touchscreen with simulated buttons.
Are you interested in security systems? Let us know in the comments below.
8-6-2021 (August 6, 2021) is the Snakiest day of the year and it’s also this year’s CircuitPython Day! The day highlights all things CircuitPython and Python on Hardware. See you there!
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.