B.E.A.M.
Biology, Electronics, Aesthetics and Mechanics

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Frans Storms

More Head-pics             Feb. 14, 2002
stepper light head
 As i have still a lot of pc-junk laying around, i got interested in the beautiful, sturdy, stepper motors of old 5.25 floppy drives. They do 200 steps to make a full circle. They were designed for 12V, but with
 little load they will run even at 3 volts. Driving them is rather complex, mostly they have 5 or 6 wires,
 1 or 2 connected to power, and 4 wires who have to be activated in the right order to make them
 turn left or right. I used (unbeamish) a small programmable microprocessor to accomplish al this, it also evaluates the data from the sensors.
 When it has found the brightest spot it shuts
 itself off for some minutes, making it possible to run for hours on a 9V battery, it uses surprisingly little
 current. The other chip is a just a driver, i could also have used 4 transistors, but this was easier. The program in the PIC processor is about 70 bytes ...

Dec. 24, 2001

winter head
 Darkness has come upon us here in holland. My lightheads are very lethargic now, so i thought of making a battery operated version. Not very beamish, but it seems i have no choice.
 To make the battery last as long as possible i built in a timer that comes to live every 2 minutes or so.
 In the meanwhile everything is shut off, the sensors themselves also, they use current(uA, but still...).
 When the system is active it turns the motors off as soon there is a change of direction. So next time  when it comes alive, and light conditions have not changed, it will almost immediately shut off. 
There's also a fototransistor that shuts off everything when there is no light at all. All in all i guess it will work for months
 this way. It has been working now for 10 days and the battery,  AAA size 1.5 V, is still in good condition. 
 The gear motor, 1:1000!, using less then 20 mA at 1.5V, makes this possible. At this voltage no chip can drive a motor so i used a H-bridge with trans'brothers' ;-)). It won't run reliably on a NiCd cell unfortunately..., that was asking too much. The circuit ( 3 hcmos chips) is pretty complex, and still experimental.  24 Dec., 2001
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