Friday, 27 June 2014

RFID reader for BiuldBrighton door pt II

The RFID reader door-opening mechanism at BuildBrighton went a bit funny a few days back. The screen was full of garbled characters and the system got into a "locked up" state, so that no-one could use the door entry system! As we were using "in-development" firmware, there was no clever trickery like watchdog timers keeping everything in check, it just locked up and stayed locked up.

We're not sure of the exact cause of the failure, but given that we noticed there was no flyback diode on the relay coil, there's a good chance some negative voltage has caused it to go screwy!

After failing (and once someone had arrived at the hackspace with an actual piece-of-metal key to open the door) it also looked like someone had had a go at fixing it - not be consulting the schematics, reading the firmware or tracing back the wires to see how it worked - more like poking odd wires into odd holes. No wonder it stopped working!

So the new v2 version is going to have to be soldered together, to stop little fingers from poking about with the wires. While we're about it, we're also using on of Arthur's really cool ethernet-to-UART modules to do the talking to the BB members website.

At about midnight last night, we finally got a working duplicate copy of the door opening mechanism. We made everything that needed to connect to anything else use a socket (or in some places, a 0.1" pitch pin header) which helped with the modular prototyping. Arthur soldered up the wires from the door into a number of "plugs" using some more 0.1" pin header and plugged it all in.

Amazingly, it worked pretty much first time (although, it had taken about four hours to solder up the perfboard, inbetween helping out other members, drinking tea, munching pizza, doing some laser training and cutting parts for another project).

BuildBrighton once again has a working door entry system.
Which means we can get back to our own personal projects for next time ;-)