Getting computer control .

Serial Port.

Because the camera already uses the parallel the only ports left were the serial. Luckily AstroVideo allows controls of these. So here I devised, a cicuirt to make use of the +/-6V. The circuit I have given is my final circuit with some refinements. The serial port only controls the transfer pulse.

To power the circuit I took some connections of the main cable input. It may be useful to use a multimeter to find these. There is more detail if you click on the image.

When I first used this circuit it wasn't reliable. After talking to Bev Ewen-smith I realised that the timings in the AstroVideo camera menu where badly wrong.

There are 3 timing options in AstroVideo (to my understanding):

The integration time (how long to expose the CCD) during this time you need to disconnect the transfer pulse. Therefore I set the serial port low.

The port finale state is how long before the software gets ready to grab a frame. This is meant for advanced amp mods to allow stuff to stabilise. I set this to zero as I didn't need to wait before grabbing a frame.

The post exposure port state is the point where the settings need to be applied to download the frame. So here the serial port is driven high.

UPDATE:

After Emails from several people, and getting hold of some other hardware:

It appears the timing settings I have chosen may only work in optimum conditions. So for some combinations of this mod and PC it may work. If you are having trouble grabbing an integrated frame this is one place to look for problems.

There are a few things that can be changed with the timings:

• Some people have changed the exposure timing in the Logitech driver to solve problems, I found this helpful on my old Pentium 133; this maybe useful for older/slower machines.
• Other peolpe have altered Exposure finale/Post exposure state to solve the problems.
• Or you can try a combination of both.

Anyway it looks as if there is no hard set approach to setting up the control of this modification due to the differences in computer systems.

You'll just have to experiment, but a good place to start would be the settings I have recommended. If you have any problems Email me.

Original statement:

[AstroVideo skips one blank frame, then captures the integrated frame. As I set the Logitech driver to give about 10 frames a second, each frame lasts 100ms. So I set the post exposure time to 110ms, this means that the software downloads the second frame presented by the driver which is hopefully integrated.]

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