For any folks who may be interested I just produced a web page
describing my PTO replacement:
http://www.karinya.net/g3txq/corsair_pto/
Although I don't expect anyone will want to replicate my design exactly,
I decided I would lay out a PCB - if only because it's fun! The details
are available from the web site, but please note that the layout remains
unproven until I get some boards back from ExpressPCB to load and test.
The final design ended up pretty much the same as my first version
except that I now use a PIC16F818 controller which has a 10-bit A/D
converter and which gives more resolution for the Offset Tuning function.
73,
Steve G3TXQ
On 10/09/2011 21:00, Steve Hunt wrote:
> 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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>
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