Optical Localization to 0.1mm? No problemo!
Quick recap, “the mission”: we want to build an affordable open source industry quality robot arm. We think we can make it out of low quality components but stick an accurate sensor on the end effector (the ‘hand’) and sidestep the huge costs of precision mechanical components. Web cams are cheap, and people already own computers capable of the required visual processing, so we think that optical localization is a better strategy for many applications that researchers, entrepreneurs and engineers might like to do – if we can get the optical localization accurate enough.
Last time we calibrated our £18 Microsoft LiveCam 3000, and experimented using Vision Visp’s moving edge tracker. We found that the moving edge required a highly accurate object and we could not build one to the 0.1mm accuracy target we set ourselves. Furthermore, the actual moving edge tracker was not particularly CPU friendly, so we decided to pursue a different strategy this time.
Can’t wait for the Raspberry Pi? Hack a router!
My Raspberry Pi delivery date is now only two ice ages away! Until the mighty Pi ships, where can you get a cheap embedded Linux fix? Please welcome the catchily named TP-Link TL-WR703N!
So what is it? For about £20 you can get a teeny embedded Linux device (in a nice little enclosure) with built in 10/100 ethernet, 802.11bgn wifi and USB. Not bad for the same price as an Arduino! The device is intended to be used as a “travel router”, you’re supposed to shove a 3G dongle in the USB socket and then use it as a personal hotspot. It’d probably be handy to have one for that purpose, but that wouldn’t be very hacky would it?
I bought one of these after Stephen Giles recommended it on the Hacklab discuss mailing list, turns out a few other members and Hacklab regulars have too. This device looks to be pretty popular with hackers, so you can expect to see it turn up in projects online (and probably in the lab too…).
Why so popular with hackers? Well, despite shipping with a Chinese web interface, it’s a doddle to flash it with OpenWRT, a lightweight Linux distro designed for routers and other low-spec embedded devices. Following these instructions on the OpenWRT site I was up and running in a few minutes. A few minutes later I was installing some packages and half an hour after that I had it configured as a client on my wifi network.
So what can be done with it? With OpenWRT installed, you can use it as nature intended and do some routing, making a nice small router/WAP. Or you can install packages to enable it to be a file server, using a USB flash disk or hard disk to make a tiny NAS box. Or you could attach a USB printer and make it a print server. Or you could plug in a cheap webcam and stream video. Or, and this is where it gets interesting, you could hook up something to the device’s onboard serial port (some soldering required…) and internetify an LCD, or a temperature sensor, or an anything really. After the flashing LED, the UART is the embedded hacker’s best friend!
Sold yet? You can buy them from eBay for <£20 shipped to the UK from China. They come with a US power supply but can be powered via micro USB.
I’m not sure what I’m going to do with mine yet, any ideas?
May Music Night this Friday
This Friday, 18th May, is our monthly music night, starting from around 8pm in the lab. Come along to talk about music, hacking, and make some noise! The month before last I wasn’t there, and I missed out on Andrew and Tom’s resistive fabric synth, and James and Matt of Madlab making instruments out of jelly. Don’t make the same mistake I did: make sure you come to the lab on Friday!
This month Gareth is going to talk about using cSound to create sounds on your computer, and I hope we’ll have some live performances from anyone who fancies it. There’ll also be the usual blether and working on hacks throughout the night.
Bring your own hacks, ideas, news, and performances.
Hope to see you there 
Alex
Acrylic boxes for Rasberry PI
The guys at Shropshire Linux User Group have been busy designing boxes to put your Rasberry Pi in. Well, that is if you are lucky enough to have one. I don’t think I am far enough along the queue to get to place an order yet 
Damn I want so bad, I want one more than I wanted Lego when I was (twenty)8.
I am sure we will be cutting a few of these on our laser in the coming year!
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Hacklab status: OPEN!
