Tweaking the exposure time of a webcam.

[pteranodon]

Hi, people.

I would like a source of how to teak the exposure time of a webcam. Recently I recovered an old web cam from the garbage of my office and for my surprise it works perfectly. It is a
VCOM NetCam PD-308 webcam (http://www.verycom.com.br/produtos/proddetail.aspx?id=pd308) with a broken case but the circuitry is just fine. The chipset is an Etoms ET31X110 and the sensor is a CMOS chip whose number I currently ignore.

Probing with my oscilloscope I was able to identify the exposure signal and I noticed that it is software controlled. I mean, the driver of the web cam controls its exposure time. My question is: Is it possible to configure the driver to set up the exposure time to, let us say, 2 seconds or is there a software able to do so? Or do I have to build an oscillator circuit to force the desired exposure?

I just want to take my first steps in astrophotography by playing with a cheap webcam. I do not expect great photos, but just to get started with the principles behind digital imaging, et cetera.

Thanks for any help.

[Mainframes]

I don't know about your particular webcam but here is a mod page for the Philips ToUCam Pro II, maybe it will give you some sort of a helping hand. I have actually managed to do the mod, I just need a laptop to go with the camera!!!!

http://www.philip.davis.dsl.pipex.com/tcp2_mods.htm

Also helpful is this nifty piece of software to go with the mods:

http://www.pk3.org/K3CCDTools/

Hope this helps......

[pteranodon]

Thanks, Mainframes. :)

[Evan]

I have a Compro PS39 and made a few mods to it. In particular one mod that is applicable to most webcams is to reduce the level of the system clock signal. It will normally be 5 volts or close to it. With most chipsets you can get away with slightly over 3 volts and it will still function. On my PS39 it greatly reduces clock noise when I have the gain cranked to max. All it takes is to find the clock oscillator output and put a resistor divider on it. You will need to cut one trace.