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Re: elevation screw jack





On Sat, 20 Jan 2001, cahill wrote:

> Hi ,
>
> I've bought a elevation screw jack for a good price but i don't know
> how i should make a position readout that's accurate and analog .
> (so i can use it on a tracking interface that recognizes a zero to 5
> volts input)
> The elevation screw has a end and beginning contact and has a contact
> that gives pulses when turning the motor in or out.
>

Here's how I'd do it:

Use a PIC microcontroller with a built in D/A to provide the 0 to +5.

Connect both contacts and the pulser to the PIC chip.  Have the chip, upon
start up or whenever you send it a "resync" pulse of some sort, swing the
dish to the beginning using the "Start" contact as an indicator of this.
Then, have the chip start moving it out to the other end while counting
the pulses.

This will give the chip a scaling factor and a "volts per degree" factor
to start on.  It also ensures that everytime you power up the system, it
starts from a known point.

You can then send the chip an "up" or "down" command through one of the
other digital I/O pins.

PICs are wonderful things....:)


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