gary wrote:Harry, you have the makings of a great Z axis for your CNC machine there.
I wish i am a long way off making something like that .
My thinking so far since i have added magnetic field sensors to the drum
2 for testing one any ordinary reed switch and the other out of a beta vcr which seems to change resistance to a magnetic field so i am trying that out either side of the drum {think it was used for tape stop}...could go with lots of ways with light but have these handy..so going magnetic (also lazy to drill a hole in the HD platter!...was going to try one or 2 old relay coils with the magnet on the drum as now but trying the above first .
Well this on off or resistance change as the drum rotates i hope to trigger a monostable 555 timer the red led on my board i will use this monostable to speed up and slow down the Led arm( depending on the drum speed}, since i am using one pulse per drum revolution 15 revolutions of the drum per second 15hz should give me in movement down on the led arm 15 lines space i hope ! so after 8 seconds 8 times 15 lines should give 120 lines of good old classic SSTV.
So i am off to hoook up the monostable and see what happens .
I think i could be in trouble in that it may work in the speed way but may expect a longer drum i might have overlapping lines due to raster line thickness..one of those things see what it does when it does it
I have orded UV leds as it might work better since every one playing around with glow paint seems to be using these my white led might be emitting part of this freq along with every other colour.