I suppose there's a reason you're not simply using the hour hand from a strong clock module? http://www.klockit.com/products/dept-157__sku-AAAAG.html The nice thing is that these are coil actuated, so if the timing isn't right, rip out the circuit, and pulse the coil yourself. Put it on the hour hand. The second hand is moved 1/60 rev each pulse, the minute hand goes 1/3600 rev per pulse, and hour hand 1/216,000 rev per pulse. The advantage above a micro-stepping stepper motor is that you don't need current between pulses, and in fact you could run the whole assembly off a AA cell for the year. Not to mention much higher resolution and accuracy than the microstepping stepper. Not that it matters much since you're running the laser continuously... Perhaps there are other constraints that this doesn't meet, but the high-torque clock in the link above may be worth considering. If it doesn't have a spot for a second hand, it is likely that the gears still provide 1/216,000 rev per pulse to the hour hand so the circuit is the same for all the clock modules. Sounds like a fun project. Good luck! -Adam On 12/20/05, Peter Todd wrote: > On Tue, Dec 20, 2005 at 11:21:10PM +1300, Jinx wrote: > > I wonder though if 5mW is going to be enough. (I notice Digikey > > describe the 38-1010-ND as "4.8MW" but I'm guessing that > > should be mW !!!). 20mW might be more like it if the display > > starts getting big and the dot has to move around a lot > > It's going to be stationary actually. See, what I'm doing is mounting > the laser to the shaft of a stepper motor. Then I *very* slowly pan it > across a wall. Each 12 hour period the laser dot will make one trip from > one side of the wall to the other. The whole assembly is mounted into > the ceiling of a room and some control lines and power is run behind the > wall to a control panel somewhere. The only tricky part is microstepping > the motor for a sufficiently high resolution, I have a 400 step/rev > motor I'm using with 64x microstepping. Actual realised resolution seems > to be maybe 1600steps/rev. > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist