RFID garage door opener + OLPC fixing + First hands on Raspberry Pi + Reprap Success

A Great Saturday down at the TechSpace.

RFID door opener:

We finally connected the RFID reader up as an additional means of entry to the TechSpace.
RFID keys work in tandem with the existing “Android phone with pin code” entry method. This is great because RFID is many thousands of times more secure than the pin code method. RFID now allows members to enter the TechSpace with a swipe of their key cards instead of typing in their pin code. RFID keys are authenticated against our central MySQL database, if approved it opens the garage door and logs who opened the door, based on who the card was initially registered to.
Gavin soldered up our door opener so it’s much more stable now – no more loose wires!

Here’s a video showing the RFID opener in action:

We had a small glitch whereby the Arduino that is attached to the RFID reader wouldn’t talk over ethernet to the Arduino that controls the door, but we could connect to both Arduino’s from laptops. The problem? Both Arduino’s had the same MAC address set! The code running on both Arduinos came from the same source, and we simply forgot to give each one a unique mac address after setting a unique ip address. That took a while to figure out 🙂

Another thing we’re a little stumped about, the RFID Arduino will not work unless it is powered via USB from a computer, if we power it without a computer it does not function. Strange! It might have something to do with the Arduino trying to send serial debugging to a computer? meh.

How Stuff Works: OLPC

We had a very sad looking OLPC in for repair. Lots of melted parts 🙂 Great opportunity to pull it to bits and find out how it works.

We’ll be printing a new OLPC X badge for this laptop, the other one melted 🙂 haha.

Raspberry Pi:

What a surprise to see one of these beaut little devices plugged in when I arrived. Running debian it was surprisingly responsive. This Pi will most likely become a media centre plugged into the back of the TV. Here’s the video:

Can’t wait to connect some goodies up to my Pi when it arrives!


The Reprap was giving us some heating issues. Looks like one of the thermistor wires is loose on the Sanguinololu end. Got that sorted rather quickly. Next problem is our uneven bed, I think we’re due for a new bed (one with adjustable screws on each end). We also had a great tip from a fellow Brissie hacker about an adjustable end stop, will be printing one of those for sure.

Another first for us today on the Reprap was continuing a 3d print job from half way. The print job stopped at 5.7mm (computer froze) and it was a very nice (and long) print so far. We didn’t want to scrap it and start again, so we decided to try restarting it from 5.7mm and continue the print as if nothing happened. We made a copy of the .gcode file, and then removed all lines from Z0.1 through to the line before Z5.7. Pumped this modified gcode file into pronterface and hit print. It worked! The printer homed itself again, the hotend heated up, then it moved straight to Z 5.7mm  and continued printing the next layer on top of the half printed object. It stuck perfectly and the job finished 10 minutes later 🙂

I think I might write a small script to help with the gcode modification next time we want to re-start a print job from half way.