Modifying a webcam for long exposures

I've spent the past couple of nights performing what amounts to brain surgery on my webcam. A few people had asked me about this so I thought I'd document my experiences. Unfortunately the procedure involves working on sub millimetre components which are impossible to photograph easily so you'll have to make do with my description and some links which explain the process.

WARNING: In order to make this modification you need to have the ability to solder the tiniest (sib millimetre)components and make simple circuits from a circuit diagram. You WILL need to have done a bit of soldering before. If not you will almost certainly destroy your webcam and of course as soon as you open your webcam your warranty is out the window so be warned. I have already destroyed one webcan by spilling molten solder all over the pins of one of the tiny integtrated circuits inside. You can buy pre-modified webcams reasonably priced for not much more than the cost of a couple of standard webcams.

Why do this mod?

Webcams have proved to be an invaluable tool to astronomers allwing high resolution planetary imaging to be done by amateurs providing the kind of quality previously reserved for professional observatories and HST etc.

Out of the box webcams only allow for very short exposures to be taken typically 1/30 of a second is the longest they are capable of. A guy called Steve Chambers discovered that by modifying the circuitry a little and it is possible to do unlimited exposures. This extends the possibilites greatly by allowing deep sky objects to be captured. The longer exposures also allows webcams to be used as CCD autoguiders in conjunction with a PC or laptop.

Whats the process?

Basically when you open up your camera you will find two important IC's inside. Typically these are the Sony CXD 267AN Vertical clock driver and a Philips SAA8116HL IC. The most difficult part of the operation involves lifting 3 or 4 of the 0.4mm IC legs and soldering wires to them and to even smaller copper traces on the tiny circuit board. Once you have successfully done this all that remains is to make a simple circuit up on veroboard and mount the whole thing inside an appropriate housing.

What are the pitfalls?

In other words, how do I thrash my camera? There is lots of ways you can destroy the webcam doing this. Typically by overheating the IC's while soldering, by making solder bridges where there should be none, by damaging the ICs with static from your body or by breaking off pins on the IC. Some can be repaired obviously some cant. I actually broke one of the pins while attempting to solder a wire to it. However I fixed it by using a conductive trace pen to draw a trace from the pin socket to the top of the IC and then attaching the wire with hot glue to the new trace. Solder bridges are a more challenging problem. DOnt try to solder them off or you may just imbed the solder deeper, use a fine needle to pick away the wayward solder.

So what are the nitty gritty details?

The actual procedure is slightly different for different cameras and in fact even with the same camera there are often a couple of ways to do it. See the links at the bottom (particularly Steve Chambers website). Others have documented it with photos etc and makes the process easier to understand.

So far I've managed to lift all the right pins and attach wires in all the required places. All thats required now is to make the little control circuit, fire it up, and hope to God it still works:)

Links

Steve Chambers - www.pmdo.com
Martin Burri's Quickcam Mod - mypage.bluewin.ch/bm98/l3k/modification.htm
Toucam Pro LX mod - www.philip.davis.dsl.pipex.com/tcp2_mods.htm

Free software for webcam autoguiding - www.barkosoftware.com
(also works with non LX modded webcams but restricted to the brightest stars)

Sources for components;
www.radionics.ie
www.maplin.co.uk
www.peats.ie

I'll add more to this as I think of it.


[/b]

Have you finished the operation Dave:)
if so how good/bad do you find the noise, and are you going to put some sort of cooler on it or can you leave it as is???
This is something I meant to get around to, but like everything else it'll probabily end up been done next year.

I also did abit of reading, and you'd need a steady hand to do this, but its possible.

I also did abit of reading, and you'd need a steady hand to do this, but its possible.

Yep and nerves of steel too. Its hard to over emphasise just how small the componens are that your working with. I have a slight tremor in my right hand which makes it even more difficult. I have to wedge my hand against something just to get it steady enough and then hold my breath for long periods of time!!

Dave. I'm just finishing it off now. Built the control circuitry without any major hassle, just to attach it to the new four wires coming out of the webcam. Solder a parallel connector to the extra cable and test it and hope it all works!!

Ahh, I love the smell of burning solder in the morning. :lol:

Are you been carefull about the wires themselves, I have a vague memory a while back that if you run thbe wires correctly, it'll actually help reduce noise.

I also dropped blobs of solder onto boards, the solder sucker came up trumps there. Just make sure you dont heat damage anything.
What you really need for this is one of those magnifing kits with crockadile clamps to hold the board.

Any surgeons out there, this would be a nice little challenge for you.

I have a spare DG418 ic if anyone is trying the Phillip Davis mod.

Well I got it all together, hooked it up to the laptop and guess what!! It works (I think)!!!!! Frankly I'm amazed it worked first time. I've just done a test in a dark room without a lens!! and I can clearly see the difference between normal webcam exposure and long exposures. I can even see the difference between different number of seconds exposures.

Dave I'm not terribly worried about noise to any great degree because the sole function of this webcam (in LX mode) will be autoguiding. However I will be installing a 5V fan in the case and also I noticed that on the quickcam pro 4000 there is an aluminium heatsink under the ccd which could easily have another heatsink attached to it, so I think I might to that. I'll need to get hold of some fine nylon screws to attach the fan tho. Dont want vibrations ruining my guiding!!

Woohoo I'm a happy camper!