On 7/4/15 7:53 PM, Hal Murray wrote:
[email protected] said:
Exactly... I've got an array of mirrors on az/el mounts (two servos
stacked) and the reflection from the mirrors on the wall forms the display.
How many pixels in that display? Or what is the unit of quality measurement?
What sort of ADEV are you aiming for? If your goal is solar time rather than
TAI or UTC, you should be able to get pretty good.
Prototype is 6 pixels to demonstrate concept and work out the bugs. Long
term, probably several dozen.
Time Accuracy? better than a second
Turns out, having done some experimenting, the real issue is angular
accuracy. RC servos aren't all that great, and have significant jitter
(probably not an issue in their design application which tends to have
good mechanical low pass filtering). They're cheap and easy to use (as
in, I had a bunch in the garage I could cannibalize out of another project).
But if you have 3x3 inch mirrors (call it 7.5 cm), and want to create a
picture on the wall that's, say, 10 meters away, you really need angular
pointing of 0.007 radians.. that's about 1/2 degree. An RC servo has
roughly 270 degree rotation corresponding to 256 steps of PWM (in the
Arduino implementation).
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