This paper describes the replacement of the ICX098 CCD of a Philips Vesta Pro Webcam with a Sony ICX414 CCD to produce a high sensitivity, low noise astronomical imager capable of taking long exposures.
The modification is along the same lines and owes a lot to Steve Chamber’s ICX424 modification. I believe that Steve’s design has been shown to work in the Vesta Pro, ToUcam Pro and Logitech 3000 webcams, so I would expect the ICX414 to work in these donor cameras, but I cannot guarantee this. One point to note is that the ICX414 is a much larger chip (4 times the area) than the ICX098. Whereas it is may be practical proposition to mount an ICX424 in place of the ICX098 I have found it necessary to mount the ICX414 remotely.
I have named this modification the SC4 as it is a logical extension of the ‘SC range’ and because it owes so much to the innovative work of Steve Chambers.
SC4.1 – ICX098 based webcam with ICX414 CCD transplant
SC4.2 - ICX098 based webcam with ICX414 CCD transplant and SC1 long exposure modification
SC4.3 - ICX098 based webcam with ICX414 CCD transplant and SC1 long exposure modification and 2X1 binning.
Stage 1 – Preparation
I will describe the method that I have used to modify a Vesta Pro camera, but I would expect the modification of ToUcam and Logitech variants to proceed along similar lines.
You will need:
- A donor ICX098 based camera
- An ICX414AL monochrome CCD or ICX414AQ colour CCD (untested in this mod, but independently proven in the SC3 Mod) The only place I think the CCD's can be bought in single quantities is Framos. http://www.framos.de/www.dir/en/start_en.html
- A secure means of mounting the CCD (see below)
- A 1 microfarad capacitor rated at greater than 16V
- Parts for your favourite version of SC1 Mod
Like the SC3 Mod, all that is required is the addition of one capacitor The CCD is no longer running within spec, but it appears to work correctly in practice
The connections are as follows:
ICX414 Pin TO Webcam Pad
3 to 2
4 to 3
5 to 1
7 to 6
9 to 7
10 to 6 via 1uF capacitor
12 to 8
13 to 12
14 to 5
15 to 10
16 to 13
17 to 14
20 to 11
21 to 8
Also see fig 1. below.
Due to the size of the ICX414 chip it is not really practical to mount it directly on the webcam’s circuit board. I decided, after attempting a wire-wrap solution, to design a printed circuit board that could be plugged into the Vesta’s CCD circuit board using headers. Whichever approach you take, using 0.05 inch (1.27mm) headers is recommended as it makes CCD removal easier and reduces the risk of thermal damage due to over enthusiastic soldering.
I obtained suitable headers from Radio Spares. One pack of each should suffice.
I obtained the materials for making the PCB from Maplin. The laser printer etch resist film was particularly successful.
AB15R Press-N-Peel PCB
I designed the PCB layout* using a coverdisk PCB routeing application.
*shown flipped LR in preparation for printing.
The first step was to build the standard SC1 modification. Details can be found at various locations on the Web. If this is your first modification, I suggest that you attempt this before ordering the ICX414, as successful modification to SC1 standards will qualify you for the next stages. Once you have completed the SC1 mod test it fully until you are satisfied that it is working correctly, i.e. the camera is integrating in long exposure mode and webcam mode.
Please note that you could replace the ICX098 with the ICX414 without modifying the camera for long exposure if you intend to use it as an electronic viewfinder or guider.
The next step is to remove the ICX098. You can either desolder the CCD or cut it off with a small pair of side cutters. Although it ‘feels wrong’ to destroy a perfectly working CCD, I would recommend the latter as you will end up with a CCD PCB that is in better shape, without the risk of thermal damage to the surface mount components. Having said that I have desoldered a CCD from a Vesta. It took me three evenings of fume inhalation, but it was ultimately successful. You decide. You can also remove the LED and Microphone without ill-effect. If you attempt a ToUcam mod, then I can recommend desoldering the CCD, as it is surface mounted.
You should now have a donor camera ready to accept the new CCD. The following images show my solution using the daughterboard. The original ‘lash up’ using strands of wire wrap to connect between the headers worked, but was fragile and prone to noise. The daughterboard allows you to control the routeing of the ‘analogue’ and the ‘digital’ sides side of the CCD away from one another.
The final stage is to mount the assemblies in a suitable case. The PCB approach seems to be pretty immune to electrical noise, so either a plastic or metal enclose will suit. I chose to mount the camera in an alloy case as shown below. This has the advantage that the case can used to cool the CCD either naturally, though direct CCD-Case contact, or using a small TEC directly placed behind the CCD. It is also provides a very rigid mount for your your optics. One point to note is that a metal case should be electrically isolated from the webcam’s earth plane otherwise noise can be induced into the CCD output circuits.
The camera could be made even more sensitive by applying Steve’s 2X1 binning modification, though I haven’t tried this.
The amp glow from the ICX414 is not significant for integration periods below about 60 seconds. The limited sky tests at my site in the rural (?) UK South Midlands indicate that integrations of 60 seconds would be a practical maximum. I recommend that you try the camera without a amp switch before attempting an Amp-Off modification. I would be a shame to spoil the excellent signal to noise ratio just to increase the dynamic range at the periphery of the imaging area.
Copyright Greg Beeke and Steve Chambers, April 2003