more DIY, mods and a writeup of the spc900nc lx mod

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more DIY, mods and a writeup of the spc900nc lx mod

Postby reggie » Sat Jun 07, 2008 6:30 pm

Hi Gang, just thought I'd let everyone know of my experiences in building stuff this week with a little write up of my spc900nc LX mod and the parallel to serial adapter just to clarify some points through my time doing it :)

I made the parallel to serial adapter for the LX mod, nice and simple and all fits inside a nice little enclosure maplins do, I also finished the EOS to serial adapter (broke a leg on a chip had to wait for maplin to restock) decided to put the circuit on a little piece of breadboard in a little project rather than try and stuff it all into the DB9 enclosure.

My favourite mod of the week was getting enough clear sky to put the wedge a friend and I built (had help from more friends with the design too) out and test it, it's a simple fixed tilt plate wedge, with the azm axis having a few degrees of adjustment. I had to make a few adjustments to bolt lengths and dremel out parts of the tilt plate so the putting the scope on the wedge didn't foul on anything.

I had a couple of issues with algnment, my fault for not knowing the procedure, well some of it is a bit ambiguous in the manual, I settled on a simple 2 star EQ align and happily slewed off to a few stars, it behaved nicely putting everything in my FOV, I was using my 25mm plossl so not the best test, but the fact that it knows where itself is and the objects I'm looking for are with my shoddy first alignment things can only get better from here :) 2nd night out with the scope, still using the 25mm plossl managed to keep arcturus in my FOV for 2-3 hours, so about 2/3rds the RADIUS of a 25mm ep drift in 2-3hrs, still not the best alignment I can get but its got a lot of promise by the looks of things [8D]

and now for the blurb about the spc900nc LX mod and parallel to serial adapter.

I got the information for my LX mod from [url=]HERE[/url] on Matthias Meijer's excellent tutorial page, It will give you instructions on how to dismantle the webcam, and about 2/3rds of the way down the page you get the circuit diagram for the 4066 chip which can be found at [url=]MAPLIN[/url] item code QX23A, just below the schematic are some pictures of how he soldered the resistors onto the 4066 chip, very simple to do, I just made sure mine looked like his and all the solder points were as per the schematic. see below for a picture of my 'dead bug'

Just below the "dead bug" picture is a picture of each of the circuit boards, ignore any references to pin and pad 10 (unless you really feel the need for a physical switch to start exposure, I'm controlling mine purely via the PC) but pay attention to the pin/pad 8/13 references, I have no idea why he named them pin 8/13 and pad 8/13 just make sure the orientation is correct as per the picture, just make a notch in the female connector on one board and bend the pin on the 2nd board :)

There is also the schematic of the connections to the outside world, as I mentioned previously, ignore the pin/pad 10 references unless you need a real switch instead of a software one. Just take the 2 wires (lx and USB gnd) out to the correct pins on a 25pin Dtype female connector. that should give you parallel port control over long exposure in all of the astro capture software.

If you want to take it one step further, you could convert the parallel connections to the correct voltage for serial port control via a [url=]simple SC mod parallel to serial adapter[/url] found on the k3ccd tools website, its not true serial, its just correcting the voltages between the 2 so that serial voltages can be used to trigger the correct pins on the parallel port without anything going bang.

Ignore the switch on pin5, the astrocapture software will deal with it, I couldn't get any 547 transistors(code QQ14Q) from maplin, so I substituted them for [url=]THESE[/url] BC546 transistors (code N57AC) instead. Although I haven't performed the amp off mod yet I did include the pin 4 amp off circuit in my adapter so that it's ready for when I do the mod at a later date.

All pretty simple to do, it took me ages because I was learning how to use the soldering iron, couldn't get my solder to flow freely to start off with, now I'm sorted I reckon that mod should've taken me 40-50 minutess or so if I was taking my time being the n00b solderer that I am.

Next to do is give the wedge a coating of something weatherproof, get speed control on the focuser, see if i can get my homemade finder scope working well enough to guide and see if the wedge is good enough for some long exposure astrophotography, onwards and upwards [:D]

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