Having learned a little about PICs and what they can do, and inspired by
N4YG's DDS system, I though I'd also learn a little about DDS
technology. So I set about trying to build a "drop-in" DDS replacement
for my Corsair II PTO. I though folks might be interesting in seeing the
results!
Here's a photo of the parts:
http://www.karinya.net/g3txq/corsair_pto/pto_parts.jpg
Left rear is a hand-wired prototype board containing the PIC controller
and a DDS buffer and low-pass filter.
Left front is a pre-assembled board containing an AD9851 DDS chip,
reference oscillator , and low-pass filter - available from eBay
Right rear is an identical enclosure to that of the original PTO cut
from aluminium channel
Right front is the optical encoder
Here's a top photo of the complete assembly showing the DDS daughter board:
http://www.karinya.net/g3txq/corsair_pto/pto_top.jpg
And a bottom photo showing the PIC board:
http://www.karinya.net/g3txq/corsair_pto/pto_bottom.jpg
This was only ever intended as another learning exercise. The DDS works
exactly as the PTO does, and mounts with the same fixing holes. There is
no Split capability, but it responds to the normal Corsair Offset signal
and the Shift signal. The only nod to modernity is a 5kHz/turn tuning
rate which speeds to 50kHz/turn when you spin the knob quickly!
I'm still checking out the operation. I doubt I'll go to proper PCBs,
but it's nice to know that if TT ever run out of re-build kits I can
drop this in as a "minimum effort" replacement.
73,
Steve G3TXQ
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