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1004 USB Mod

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Introduction.

The Philips Vesta, Toucam and QC3000 pro all make good astro imagers when modified to take long exposures. Much of the reason for this is their use of Sony HAD or super HAD CCD’s. These have greater sensitivity and lower dark noise than similar CCD’s from Sharp etc. However the super HAD is not the most sensitive CCD Sony makes. The fabled Sony ex-view in its unfiltered form boasts quantum efficiencies as high as 85% and a broad response from blue to near IR. This chip easily competes with latest enhanced blue Kodak offerings found in expensive astronomical CCD cameras. In contrast to the Kodak chips the Sony ex-view can be found in modest security cameras. In 2001 Jon Grove published details to convert the ex-view based 1004x board camera to take long exposures. This is undoubtedly the most sensitive camera to come out of QCUIAG/ASTROCAM.

Over the following months the mod was improved further to allow the full resolution of the CCD to utilised.


A small fly in the ointment.

While this camera has produced some great images it is relatively demanding on hardware. The 1004x camera produces up to 30 full frames per sec. Jon’s modification does require a PC and video card capable of analysing all the frames from the camera. This tends to mean around 600Mhz+ processor and a PCI capture card. Obviously this then excludes older laptops!


The answer?

This page contains details to use a 1004x-JG with a USB Capture device and removes the need for a fast PC. The additions to the normal JG mod are a board with some logic chips and a line from the USB box to synchronise the capture process.

How does it work?

The Hauppauge products are based on the NT1004 chip. The data sheet is here. The first thing to say is that it doesn’t offer a magic solution of the limited bandwidth of the USB connection. In the case of the modified webcams images are collected at 640x480 from a 5FPS stream. This still requires quite a lot of compression and it is fortunate that image quality is a good as it its. Moving to 30 FPS over USB means 6 times move compression and is not supported by the NT1004.

The solution is to use twain capture. Here 2 consecutive fields are collected in the USB capture box memory, interlaced, then slowly, and without compression, transferred to the PC. The trick is to make sure that the fields collected by the twain capture contain an exposed field. Despite having a good poke around in these devices I have not found a signal which will indicate that a capture is imminent. However, with the right bits of logic, a signal can be found to indicate that the capture has just begun. This means that an exposure can be ended in time to get an exposed field into the second field captured. If the 1004 is run in its most sensitive 2x1 binned mode then all that is required is to remove the interlaced unexposed first image. For a full res image the procedure is repeated to collect the second field.

A second benefit of this method is that it greatly relaxes the timing accuracy required at the PC end as the exposure end is now handled in hardware. So I hope we will find that any USB enable PC or laptop will be compatible.


You will need.

A 1004x camera, a Hauppauge USB winTV or USB live capture device and

  • 3X 12V relay

  • SN7406

  • 6x diode eg 1N914

  • 3x 0.1uf ceramic cap

  • 11 x 10K resistor

  • 10K Pot

  • 7x 470 ohm resistor

  • 2x 100K resistor

  • 2x 2.2uF electrolytic cap

  • 1x 74HC74

  • 1x 74HC123

  • 1x74HC08

  • lots of wire, connectors and patience.


Start by modifying the 1004x. This is well described on Jon’s pages. The picture here shows the connection points I have used. The gain pin needs to be lifted if you would like to use manual gain control (a good idea) also you will need 5V from the 1004X board to power the gain circuit (do not power the logic board from this 5V supply).

The Amp+Vdriver supply, V3, Vh and amp lines need to connected to the relay board which is only slightly changed from the JG circuit. The optional gain control circuit is simply this.

Next up is the USB device. From this we need 5V and 0V from the USB connector and the NT1004 chips write line. The pin spacing on the NT1004 is kinda close, the wire to this write signal is better made at or close to the memory chip (pin 13), picture here.

Finally the logic board. The circuit diagram is here. Take your time with this as any wrong connections can take a while to find. (Nb if the relay board is disconnected from the control board the camera should work normally)

After completing all the above you will have the most sensitive unconventional astro imager ever connected to a laptop! I guess you might then like some software to run it! The package here is simple, but I hope, effective.  (Due to a small programming error the program will not run as is.  You will need to edit the config.dat file that will be in the directory the program installed to.  Usually Program Files/Highlight.  Use notepad to change the second line to c:\   ). 


Copyright

The novel information on this page is copyright. It is forbidden to use this information for profit. Should you receive any money as a result of performing this mod or selling a modified camera send the money (less parts) to www.msf.org.

Over the last year I have received some requests from people who are looking for a way round these restrictions. I would like to take this opportunity to specifically state that it not OK to give modified cameras away free with other products nor is it OK to charge people for you time when going mods for others.

Any individuals of companies wishing to produce commercial products based on these modifications please contact me directly smunch@clara.co.uk .


Please abide by these restrictions, as this will ensure that future developments can disclosed in the same way.

Steve Chambers

 

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Copyright 2006 Steve Chambers. All Rights  Steve@pmdo.com

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