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Old 29-07-2015, 12:24 PM
Ilmenite (Nick)
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Ilmenite is online now
Join Date: Jul 2015
Location: South Lake
Posts: 9
DIY electric (auto?)focuser...

Having had a look around at the assorted commercial and homemade electric and autofocusers, it seems that there should be a very simple way to make an electric autofocuser. In the crudest version, the electric focuser consists of a single on-off-on switch which controls the polarity of the voltage to a geared DC motor mounted on the telescope focuser in some way. To this can be added a speed controller which varies either voltage or duty cycle (PWM) to slow the motor.
Autofocus is simply the computerisation of the switch (and possibly the speed controller) to move the focus one way of the other according to some quality algorithm.
Thus, coupling the two aspects together should be very simple, the computer controlling the switching aspect. The projects I have seen to do this invariably seem to use the ASCOM standard so that they can be driven using assorted software packages.
My thought is to pick a very simple (and cheap) USB relay controller with two relays and write an ASCOM compatible driver for it. This will then do pretty much everything an autofocuser is required to do (move in, out). A third relay could give a high-low speed control.
Does anyone else have any thoughts on whether this is possible, or has already been put into operation?
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