====== Custom Cable Making: Adapting the ST-7 Astronomy Camera ======

=====Objective=====

The goal of this project is to demonstrate how to adapt a device to work in a system when the proper cabling is not present.  

=====Materials and Reading=====

Before you jump into creating adapter cables, and modifying power supplies, it is important to document and KNOW (inside and out) the requirements to accomplish your goal. The first step was sourcing out proper documentation.

====1)  The manufacturer's documentation.====
	a) Sbig documentation site: http://www.sbig.com/pdffiles/
	- this contains every manual for the Sbig line, it includes wiring diagrams, drawings, and technical notes.

====2)  Cable pinout reference.====
	a) http://www.electronic-engineering.ch/microchip/datasheets/pinout/pinout.html

====3)  Tools====
	a) Small "eyeglass" type screwdrivers
	b) Allen wrench set (standard)
	c) Soldering iron
	d) Flux core solder
	e) Heat shrink tubing
	f) Soldering fixture with magnifying glass
	g) Multi meter

====4)  Hardware (PURCHASED)====
	a) (1) 3' long DB-37 extension cable (male and female ends). $6.99
	b) (1) DB25 FEMALE SOLDER D-SUB W/ BACKSHELL - $1.99
	c) (1) DB25 MALE SOLDER D-SUB W/ BACKSHELL - $1.99

====5) Hardware (FOUND)====
	a) (1) ATX power supply - removed from old computer
	b) (1) DIN5 male cable - removed from old "wall wart" power supply


=====Background=====

In this particular instance, I purchased an Sbig ST-7 CCD camera for use at the Eileen Collins Observatory.  Upon receipt of the camera, I noted that the data communications connection was in the form of a parallel db25 port, the power port was a DIN-5 format, and the auto-tracking port was DB-9. 
 
The unfortunate part was that none of the cables or the power supply were included with the camera.  I will document how I was able to build the proper cables, adapt a power supply, and set up guider communications for virtually no cost.

=====Procedure=====

Determine the scope of your project.

To adapt the camera to work at the observatory, I required a DB25 cable from the camera that adapts to a DB37 cable running from the dome to the control room, back to a DB25.  Secondly I needed a power supply to run the camera.  Finally I needed to adapt the camera's guide port to work with our telescope.

This seems like quite a bit, but lets break it down one project at a time.

===1) The power supply.===

This to me was the most critical item needed, as the camera could not operate without it.  To determine the requirements for the power supply, 

In the ST-7 user manual (http://www.sbig.com/pdffiles/st789man.pdf), page 51 - appendix "A" - Table A2 Power Connector

Pin Number 	Function
6,Shell 	Earth Ground
5 DC 		Ground
4 		-12V DC, 100mA
3 		No contact
2 		+12V DC, 500mA
1 		+5V DC, 2A

This happens to be the same power supplied by an ATX computer power supply.  

On the CasEdge Model: F400-A power supply, the following is stated:
<code>
Wire Color	Function
Orange		+3.3 vdc
Red		+5 vdc (32.0A)
Yellow		+12 vdc (16.0A)
Purple		+5vsb
White		-12vdc (0.8A)
Gray		PG Signal
Black		Ground
</code>

As we see above, all of our requirements are met, both in voltage and amperage requirements.

The next step is to plan out the connections, this is easily done like this:

<code>
Pin(DIN5)	Power Supply
1---------------RED
2---------------YELLOW
3---------------No Connection
4---------------WHITE
5---------------BLACK
6---------------EARTH GROUND (attach to case)
</code>

**** NOTE: While one would assume that the pinouts would be numbered the same as any DIN5 (per reference), this is NOT the case with the Sbig connector.  Sbig numbers their pins on the DIN5 from 1 to 6 clockwise while looking at the connector with the pins UP.

All connections to be soldered, heat shrinked, then taped together using electrical tape.

Now test the connections, plug in the power supply, and using a multi meter verify the voltages at the pins.  Put the negative lead (typically black) on pin 5, with the positive lead (typically red) check the other pins and make sure the voltages match the desired result, if they do not, go back and recheck your wiring.

===2) Communications Cable===

As usual, every connection needed at the observatory is an odball.  The camera needs to adapt from its DB25 port to a DB37 and back again to achieve communications from the control room to the dome.

As before, the important part of this is documenting your plan.  With 50 total soldered connections it can easily become confusing!  Lets start.

First, cut the DB37 extension cable in half and strip off about two inches of insulation, taking care not to nick or cut any of the small wires contained within.  The best approach at documenting the wires you are to use is using the standard electrical color code, as it's fairly easy to remember.

Color Code: BLACK BROWN RED ORANGE YELLOW GREEN BLUE VIOLET GRAY WHITE

Yes, that is only ten, so you will have to adapt your documentation.

Again, chart out the DB25 pin to DB37 wire color using the same method as above. Example:

<code>
M/F ADAPTER
DB25 Pin	DB37 Wire
1---------------BLACK
2---------------BROWN
3---------------RED
4---------------ORANGE
.
.
.
</code>

<code>
F/M ADAPTER
M/F ADAPTER
DB25 Pin	DB37 Wire
1---------------BLACK
2---------------BROWN
3---------------RED
4---------------ORANGE
.
.
.
</code>

Now there is a plan to follow. Which is good - because you have A LOT of soldering to do now.

The key to a good soldering job is to have a fine point on your soldering iron, and a fairly high temperature.  Only strip about 1mm of insulation off of each DB37 wire to prevent shorts later on.

Easy right?  Now that you are done with soldering (that was quick!), verify continuity, and connections using the ohm meter.  For female connections you can unbend a paper-clip and insert it into the pin hole and attach your meter to it.

Once connections are verified, power requirements are met, you can now plug in the camera, and make sure that it is operating properly, if you followed the above steps and documented everything, it should be a breeze.

=====References=====

1) Sbig Documentation Archive: http://www.sbig.com/pdffiles/

2) Tiger Direct: http://www.tigerdirect.com

3) Pinouts of Various Connectors: http://www.electronic-engineering.ch/microchip/datasheets/pinout/pinout.html