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Gregory wrote:Hi Harry,
Thanks for the info and yes I will try using the edge of the mirror to get the pulses, the simpler the better, and I can do the same for the frame sensor.
If you can please can you send me the bi-stable circuit you used instead of the PLL, sounds very interesting.
With the hard disk motor unfortunately, it is very difficult to control the speed up and down quickly as it has an extremely low torque although it has unbelievable top speeds. With DC motors and stepper motors you have lots of torque which makes it easy to control. As the 7.5 degree stepper motors are very cheap, that is the way I will go as they provide precise speed providing your clock frequency is stable.
[/quote]The only thing with the steppers, they must have low resistance/inductance windings in order to have the high stepping rates needed. The one I have measures 5.8 Ohms and that works fine past 5000 RPM with 24v for the driver, but I noticed on the web there are some with only 2.5 ohms, they should fly.
Gregory wrote:Harry, will definitely try the bistable for sync, I like the idea, its simpler in operation. Should be able to do a test on the line scan and sync with the new motor first part of next week, as I need to make a new flange for the stepper motor first. If this doesn't work than I will go for a DC motor, but I think it will.
Gregory wrote:At last have now finalised the circuits for both the line and frame syncs and motor controls - should be able to upload schematics of these in the next few days. It now remains to design the PCB for this section, to complete.
The only remaining circuit left after this is the laser modulator. I am at the moment using a linear driver for this, which is not bad, but not great. I have also now made progress with a PWM modulator, although performance at the moment is only marginally better than the linear driver
Unfortunately I blew up the last laser diode and am waiting for new ones to arrive, Does anyone know what PWM frequency to use for 60 lines 12.5 frames/sec? I have tried frequencies up to 500khz. Hopefully as soon as the new laser diodes come I will be able to finalise this too.
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