Saturday, January 23, 2010

Vacuum + Powertool foot switch

Work has been crazy lately and I haven't been spending as much time on my own projects as I'd like to. I finally got around to getting my Dremel tool and shop vac controlled with a foot switch. As I typically use the Dremel with a drill press attachment this is going to be a boon.

Wednesday, January 20, 2010


I was sick today and slept in till '3, after waking and feeling marginally better I attempted all the standard sick-person stuff but was quickly bored (TV, a good book, staring out the window at people). I decided to play around with an Arduino, Wiznet W5100 ethernet shield and some temperature / RH sensors. This is the result and here's the link. The other board is a stepper driver that was used for testing some motors destined for a reprap.

Wednesday, January 13, 2010

Fire vortex upgrade

This apparatus is just a fire-proof turntable with a variable speed motor. The puck in the center is filled with an alcohol soaked wick and set alight. With the screen placed over it a small tornado of fire blazes away for a few minutes.

The old drive system had the pot controlling a 555 that generated the clock for a stepper. Over the years (>10) some part of this system seems to have lost its zip resulting in terrible acceleration and little torque once at speed. Rather than trouble shoot what I feel was the wrong solution in the first place I went with a DC helical gearmotor and feedback via optical tach.

Repairs are nearly done, the encoder assemble has to be mounted and the controller wired up. To the left is the old stepper and driver, the new driver and gearmotor, the underside of the turntable and some encoder wheels. The print pattern for those was generated with a postscript file made by NickAmes and can be found here: postscript encoder wheel generator

Pneuman's new brain

Pneuman has peddled around the atrium for over a decade but a couple years ago he died and was forgotten.

The pneumatic cylinders on his legs were operated via solenoid valves controlled with a bunch of dumb onboard logic. This communicated over a serial connection to a 486 with the UI written in Pascal. An age-yellowed printout of it was thoughtfully included in the project folder. The parallel port served double duty; watching four pushbuttons for user input and communicating with the robot's logic over a clunky sync'd serial mux.

The PC is long gone and my OCRing of the Pascal was just for kicks. It's past time for an upgrade and in need of repair anyways. After thinking about different platforms I settled on the Arduino. I've played around with it but this will be my first install in a permanent contraption.

My work tonight started with getting a handle on the included documentation. A sizable chunk of the original project docs are missing, including the PC-side interface and power supply. Several modifications to the logic on Pneuman's frame went undocumented but were easy enough once the rest was understood.

In the interest of getting this done with as little time / money spent duplicating existing circuitry the old output section was reused. The final shield will consist of:
-6, 1/2 darlington pairs to go with the heatsink-mounted TIP31c's
-3 optical encoder inputs to locate Pneuman's current crank angle
-2 contact switch inputs to detect when he hits the end of his track
-the extra space needed for a radio module to communicate with a PC interface for guests

Currently I've got the shield populated with some power stuff and half of the output. I'll need to check a few things on his frame before I go ahead and make the encoder input section. The original design calls for op-amps with hysteresis which seems unnecessary.

Another issue has been the rubber tires disintegrating in the track over time. This might be addressed with the addition of a small shopvacpack on another output that people could control.

Tuesday, January 12, 2010

Blog established

Well it's 2010 and after several months on the job I figure a blog would be a good idea. Stay tuned for updates on my work.