[Amps] "Best" limit indicators for multi-turn, shaft-driven gadgetry

[Jeff Blaine]

Jim,

I don't have an answer for your actual question.  But the pot idea is good for another reason.  In that would open the door to an 
auto-tune kind of option (or at least, the ability to record presets which via the ADC input, could be used to set the cap via the 
stepper).  If your drive and antenna loads are stable, that would be very cool and not too complicated to code up.

73, Jeff ACØC
www.ac0c.com

-----Original Message----- 
From: Jim Barber
Sent: Sunday, August 07, 2011 4:45 PM
To: Amps at contesting.com
Subject: [Amps] "Best" limit indicators for multi-turn, shaft-driven gadgetry

I've reached the point where I need to decide whether or not to make my
YC156 project amp "remote". Because of other interests, I already have a
good selection of larger stepper motors and drive electronics, and a
good feel for how to put it all together.

What I don't have is a good, simple limit stop/reference concept for the
vacuum caps and (possibly) roller inductor. I've used drive screws and
leaf switches in the past, but don't like the mechanical sloppiness and
complexity. I've also seen optical interruptors used in place of the
leaf switches, but still don't like the mechanical complexity of the
whole drive screw, platform and guide assembly.

My favorite candidate at the moment is a high-quality 10-turn pot in the
timing belt path for each shaft, "gearing it down" so that (for example)
a vacuum cap that rotates 13 turns end-to-end would run 8 or 9 turns at
the pot shaft. Using regulated 5VDC, I could then apply the output of
the (pot) divider to a 10-bit ADC. Note I already have ten 10-bit ADC
inputs at each control processor, so that isn't as much of a
complication as it might seem.

Any thoughts or suggestions?

Thanks,
Jim N7CXI

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