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Sunday, 26 August 2007

ICX414 - based Webcam

Introduction

In February 2003 Steve Chambers made another major breakthrough with the introduction of the SC3 Webcam modification. This involved the grafting of a Sony ICX424 onto the front end of a standard SC1 modified webcam. Amazingly, this was achieved with minimal modification to the webcam circuitry. An excellent and informative introduction to the SC3 mod can be viewed on Steve's website here. The page also describes how you can obtain details of the design for your own non-commercial use.

The Camera

When Steve first published images of the SC3 I was impressed with the quality and ultimate potential of the camera, but I had only just replaced the standard CCD in my ToUCam Pro with the monochrome equivalent of the ICX098. I had also studied the data sheets for the ICX4X4 series of chips. The ICX414 looked to have similar characteristics and basic configuration to the ICX424, but the CCD size was 0.5", with 9.9 micron, square pixels. This puts it in the same league as the CCDs used in the middle to high end SBIG and Starlight Xpress cameras, and we all know what can be achieved with these.

Procrastination on my part led to my missing Steve's bulk order for the ICX424, so I investigated the possibility of trading up to the untried ICX414. I obtained a quote from Framos UK, discussed my intentions with Steve.. We were both unsure of the sensitivity of the ICX414. Theory told us that it should be more sensitive than the ICX424, but this was not borne out by the information available within the datasheets. I decided to take the plunge anyway, as the image scale was a good match for my LX200.

Initial tests with the modified camera have been very promising. The camera is very sensitive and the dark current is extremely low at ambient temperatures. The following first light image was taken with 135 mm lens at f/2.5. The donor camera is a Philips Vesta Pro, which has a lower pre-amplifier gain than the TouCam. Even so it was possible to pick up a number of galaxies with only 2 second exposures!

Since this First Light I have developed a more robust mechanical and electrical design, the results of which can be seen in the gallery pages of this site.

In March 2004 I decided to re-house my camera in order to reduce its weight and size. I also took the opportunity to implement an advanced form of my Amp-Off design, which completely separates the CCD power supply from the supplies to the pre-amplifier, substrate bias etc. The following is a brief description of the camera, which I hope will give you some ideas for your own camera, should you decide to make one.

I wanted the camera to be reasonably compact to be suitable for use with my Borg 76ED and LX200 scopes. For the latter it was important that it would not be too deep, in order that views towards the Zenith would not be restricted (I have an NGF-S focuser). I also set myself the challenge of making the height and width of the camera less than 60mm x 60mm. My ultimate intention is to build it into a turned aluminium case similar to that used by the Starlight Xpress cameras. As an interim I have built the camera into a Maplin project box (Type MB1).

The image above shows the camera, filter pocket and focal reducer along with the various adapters needed to join up the imaging train.The camera is fitted with a PK T Mount adapter. Any T Mount would do as the bayonet or male screw has to be removed. I did this by carefully filing it off with a belt sander, so that it is flush with the case. The flange allows you to fix the cut down T Mount to the plastic box with screws. The filter pocket is made by True Technology. It has a flitter ring on the rear upon which I fit a 1.25" IRB filter. This cuts out infra-red (below Hydrogen Alpha) and also protects the CCD from dust. Note that I have combined the USB and parallel cables into a single multicore. I got fed up with tangled trailing leads. It seems to work OK.

Here is an image of the ICX414 and the T Mount ring. The CCD is mounted in 0.05" DIP headers that protrude through slots cut in the plastic box. I'm still sweeping the motes of case filings off the CCD window! The shiny case plastic within the T Mount could probably do with a coat of matt black paint at some stage. Note that I was able to re-use the USB cable strain relief on the new cable. Once it has been prised off the old cable it can be slid onto the new cable an hot-melt glued in place

Here is a view of the inside of the case. As you can see the design is based on a ToUcam, but it should be possible to use other donor cameras with different cases. Nothing is mounted in the body of the case, which acts as the lid. This gives good access. I may add a cooling fan in the lid at some stage, but as the ICX414 is blessed with low dark noise, so it is not essential. The single sided PCB was designed using PCB Express software. It supports the female headers for the ICX414 and male headers to join the pcb to the ToUcam PCB. Male Headers are soldered to the ToUcam PCB to allow the PCBs to be separated. The PCB also carries the basic 4066 Steve Chambers (SC) mod plus a complete Vdd supply circuit, with Zener Diode voltage control, fed from the ToUcam's regulated 15V supply. All the components apart from the SIL resistor array are SMT. I bought the 4066, zeners and transistors from RS Components. The rest I cut of old PCBs I had lying around. I used Julian Palmers excellent site for tips on how to best make connections to the ToUcam board.The PCB and case are screwed down to the adapted T Mount with 3mm set screws. This proves very robust in practice.

If you would like to make a PCB it can be done without special tools and a little patience. I used screen prints of the PCB Express design, Press-n-Peel PCB Transfer System (from Maplin), Solder paste (Thanks Ian), ready mix ferric chloride solution and a set of Hobbycraft type drills. If you don't fancy making the board yourself, PCB Express can make them for you, at a price.

Obtaining Details of the ICX414 based camera

The ICX414 based camera is related to Steve's SC3 design, and as such I will share details of it on the same basis. Steve has kindly offered the use his Sky Survey Emailer service to distribute this design.

In order to obtain the instructions to make this modification for yourself I ask that you agree to the following terms and conditions.

  1. You will not distribute these instructions.
  2. You will not place information derived from these instructions into the public domain. If you have any improvements or tips you would like to give others I will be happy to add these to the instructions distributed, and acknowledge your input.
  3. You will not sell a camera modified in the way described for any more than the value of the parts, unless all extra money is passed to MSF or Cancer Research UK
  4. You will not sell a camera modified as described as part of a larger deal.
  5. The instructions are provides 'as is' with no guarantees of being correct, accurate or even working. You agree to be responsible for any injury or damage that results.

If you can not agree to these terms I quite understand.

If you can agree, and would like the instructions then please send a email to

greg_at_cosmicshed_dot_com

Subject: PMDO>SC4

Message must contain the exact sentence (including full stop):

I agree to the terms and conditions for the SC4 instructions.

The instruction will be send to you by email. This is an automated process. If you would like to send me an email please use the Email Me Link on the home page.

5 comments:

Ian said...

Website at SC4@PMDO seems dead. E-mail requesting modification details is bounced as site unknown. Is there another address where details of the mods can be obtained ?

Greg Beeke said...

Ian,

Let me know your email and I will send instructions.

Anonymous said...

Could you please also send the instructions to me? Also I cannot find your email address?

bogkarzi said...

Greg, The SC4@PMDO is non active, my e-mail was bounced at 2.50 EST today. Is there another site where the info can be obtained. Ian Munro

Greg Beeke said...

Send me an email to greg_at_ cosmicshed_dot_com and I will send the instructions