Introducing GangScan

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As some of you might know, I am a Scout Leader. One of the things I do for Scouts is I assist in a minor role with the running of Canberra Gang Show, a theatre production for young people.

One of the things Gang Show cares about is that they need to be able to do rapid roll calls and reporting on who is present at any given time — this is used for working out who is absent before a performance (and therefore needs an understudy), as well as ensuring we know where everyone is in an environment that sometimes has its fire suppression systems isolated.

Before I came along, Canberra Gang Show was doing this with a Windows based attendance tracking application, and 125kHz RFID tags. This system worked just fine, except that the software was clunky and there was only one badge reader — we struggled explaining to youth that they need to press the “out” button when logging out, and we wanted to be able to have attendance trackers at other locations in the theatre instead of forcing everyone to flow through a single door.

So, I got thinking. How hard can it be to build something a bit better?

Let’s start with some requirements: simple to deploy and manage; free software (both cost and freedom); more badge readers than what we have now; and low cost.

My basic proposal for such a thing is a Raspberry Pi Zero W, with a small LCD screen and a RFID reader. The device scans badges, and displays a confirmation of scan to the user. If the device can talk to a central server it streams events to it; otherwise it queues them until the server is available and then streams them.

Sourcing a simple SPI LCD screen and SPI RFID reader from ebay wasn’t too hard, and we were off! The only real wart was that I wanted to use 13.56mHz RFID cards, because then I could store some interesting (up to 1kb) data on the card itself. The first version was simply a ribbon cable:

v0.0, a ribbon cable

Which then led to me having my first PCB ever made. Let’s ignore that its the wrong size shall we?

v0.1, an incorrectly sized PCB

I’m now at the point where the software for the scanner is reasonable, and there is a bare bones server that does enough roll call that it should be functional. I am sure there’s more to be done, but it works enough to demo. One thing I learned while showing off the device at coffee the other day is that it really needs to make a noise when you scan a badge. I’ve ordered a SPI DAC to play with, which might be the solution there. Other next steps include a newer version of the PCB, and some sort of case solution. I’ll do another post when things progress further.

Oh yes, and I’ll eventually release the software too once its in a more workable state.

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