At the first place I want to thank to Steve Chambers for his excellent job on long exposure modification of webcams. As a tribute to his work the QCUIAG settles to use SC designation for modified cameras. So my Vesta 675 webcam after modification will become Vesta 675 SC. Also I want to thank to all people in QCUIAG, who participate on long exposure modification project.

!WARNING! You can use the following information on your own risk. Author is not responsible for any damage of camera or computer equipment. The following procedure was done successfully by author, but he cannot guarantee, that your modification will be successful.

!NEW! (1.4.2002) I modified my SC1 modified webcam to cooled SC2 webcam. Look here.

1, Preparation works
Link for studying SC modification:
1, Steve Chambers - Inventor of the modificaton
2, Bob White - Step by step modification procedure with nice pictures
3, Sylvain Weiller - Excellent pictures, step by step procedure (french)

2, Schematic diagram
After studying a lot of designs in QCUIAG mailing list I decided to do modification according to the next schematic:

Note: Point A and Point D connections are evident from "Dead bug" schematic diagram bellow.

This solution is prepared for Self-Guide mode of webcam for future, while beeing compatible with the current modification. The only thing needed for compatibility is to connect wires from R4 and R6 on CANON25 connector side. But it is necessary only for compatibility with Desire software. AstroSnap and K3CCDTools software enable to set the data byte for activation and deactivation long exposure.

The next picture shows a diagram of deadbug method of modification. It is modificated (according to schematic above) diagram based on Peter's Vasey diagram.

3, Tools
Because the modification work is like a micro-surgery, it requires some special tools for work. The camera parts are based on CMOS technology, so the parts can be easily damaged with static electric charge. The very delicate SMD technology requires using special solder iron for electronics with thermo-regulator. NEC D16510 integrated circuit has pin distance 0.65mm, so it is necessary to have needle-shaped soldering tip. Very fine work work requires using magnifying glass. I bought especially for the modification the special helping hand with magnifying glass (only for 5$). I think, that it is impossible to do the job successfully without it. For cutting the via to pin 13 and to scraping off the green protective coating the cutter is needed.

The list of tools:
- solder iron with thermo regulator + sharp thin soldering tip
- helping hand with magnifying glass
- cutter
- the steel guitar string "e"
- jewlers screw drivers
- Patex glue heat gun (for fixing wires on the printed circuit board (PCB))
- patient wife ;-)

Solder iron with thermo regulator	Very sharp soldering tip (less than 0.2mm)
Helping hand with magnifying glass	The cutter
Hook prepared from steel guitar string "e"	My "kitchen workplace"

4, The modification itself
I followed the very good description of Bob White Step by step instructions, but some steps I did by my own way.

a, Taking the camera apart.
I used a pocket knife and jewlers screw driver for this job. For learning this step, look at Sylvain Weiller's page.

b, Mounting 2.5mm minijack socket and switch to the camera case.
I did this step before the whole modification in order to have prepared all things after the modification work. After such delicate work a man is very often impatient to try the result of work and have no time for mechanical job. Be carefull to locate the parts not to collide the printed circuit board.

Left cover with glued switch.

Right cover with mounted 2.5mm minijack socket

c, Scraping off the green protective coating and lifting the pin 10 of D16510
Unplug USB socket and CCD part of camera from the main camera board. Scrap off the green protective coating from the pin 10 and pin 8 & 13 vias according to Bob White step by step instructions. Lift the pin 10 of D16510. For this very fine work I prepared a tool from an old steel guitar string "e" - special hook. I put this hook under the pin 10, warmed the pin with solderer and gentle lifted up the pin. Be carefull not to break off the pin.

The first test: After that I folded up the main board, USB and CCD and check the functionality of the camera. If the work was successfull, the video capture program must work, but the exposure must be independent on shutter speed. If the exposure is dependent on shutter speed, then the pin 10 is touching the pad below pin 10.

d, Cutting via from pin 13
Unplug USB socket and CCD from the main board, again. Look at Bob White instructions, because all steps are refered to his pictures and documentation. Cut the via from pin 13 with the cutter. Be careful not to cut the close vias from the neighbour pins. Don't cut too deeply, because PCB is multi-layered. Solder wires of suffcient length to points A and D. I found out that this step was much more difficult for me than lifting the pin 10. The solder area in points A and D are very small, so it is difficult to get a tin to them.

e, Preparing a dead bug 74HC00 integrated circuit
Prepare a deadbug from 74HC00 integrated circuit accotding to above deadbug schematic diagram. Glue the chip by means of double sided sticky tape to the main board (on D16510 side).

f, Making connections
Solder a wire from point A to pin 1 of 74HC00. Solder another wire from pin 13 of D16510 (take care to avoid from connecting the cutted via). Make connection from pin 1 of USB connector (+5V - red wire) to pin 14 of 74HC00. Make another connection from pin 4 of USB connector (ground - black wire) to pin 14 of 74HC00.

g, Preparing paralell port connector (Canon DB25)
I used bifilar shielded cable (for audio devices) for connecting the camera to the PC paralell port. I used two 150ohm protective resistors directly inside the connector connected in to pins 2 and 3 (they are not in the schematic diagrams above). They protect paralell port of computer, when you plug or unplug minijack connector to the camera . The opposite sides of resistors are soldered to the inner conductors of cable. Solder a shield to pin 21 of Canon connector. Solder the opposite sides of cable to resistors R4 and R5 on deadbug.

The second test: Plug USB socket and CCD to the camera main board. Plug Canon connector to paralell port and camera to USB. The camera is fully functional for long eposure now. You can test it with Desire or AstroSnap software now. If something is wrong, test all things done from the point d, to g,.

h, Modifying camera for autotracking functionality
Lift the pin 8 of D16510 using the same technic like in point c,. Solder a wire connecting lifted pin 8 of D16510 to pin 8 of 74HC00. Solder another wire to lifted pin 10 (the second side of it will be soldered to switch in next step).

The third test: I decided to do another test, to find out that D16510 was not damaged by soldering and lifting the pin 8. I tested the camera with AstroSnap software, because it allows to set the control bytes for paralell port.

i, Completing the modification
Unsolder cable (leading to Canon DB25 connector) from R4 and R5 resistors on deadbug and solder the cable to minijack 2.5mm. Solder wires connecting R4, R5 and ground with 2.5mm minijack socket on camera case. Solder wires connecting the pin 10 of D16510 and Point D with switch on camera case. Check all connections and close camera case. Take care to not cut wires, while closing the case.

The fourth test: Test all function of camera (including standard mode).
If all tests were completed successfully, then the camera is ready for astro imaging. Congratulations!

The deadbug on left and USB connector on right	NEC D16510 IC and glued wires on it
The overall look at the camera PCB after finished job.	Almost all work done.

The final result

Steve Chambers made also another modification - SC2. It allows to achieve longer exposures (up to 20 minutes) by switching off CCD amplifier during long exposures and therefore reducing CCD glow. The modification is useful only if you intend to do longer exposures than 30s. It also requires proper CCD chip cooling (reducing hot pixels). For more details check Steve's web page.

!NEW! (1.4.2002) I modified my SC1 modified webcam to cooled SC2 webcam. Look here.

Have a look at tests of modificated camera

Back to Astro Photography page

Computer generated images, real images, drawings and texts are property of the author and may not be reproduced or used without permission of author.

Last Update: 14.09.2005