Check out a very simple computer parallel port webcam switcher here.
NEW 2/27/03: added schematic with info at the bottom of page
Homemade sequential video switcher made from a Radio Shack 4017B chip. This one is set up for 3 videos in and one out. The same setup should be able to switch up to 10 video/audio inputs. When the IR channel "UP" serial port gizmo is used, it switches from one cam input to the next. I used an optical isolator made from Radio Shack MOC3010 ($2.00) chip and a couple of transistors. Note that if the video out line is used for the ground, the optical isolater should not be necessary (from what I've seen from the parallel port switcher). What is in the pix cost ~$13 at radio shack, power supply not included. Add another $4 for the serial port connector and some wire. Next plan is to add audio for each cam, which would be to add 3 more transistors/resistors. Also look at a way to eliminate the optical isolator, probably by eliminating the ground connection back to the serial port. Schematic soon come too.
Update 11/16/02: All Electronics has an "led chaser kit" (cat# AEC, $6.50) that would be an excellent start for this project. Add transistors attached between the chaser chip and leds, like the setup in the "el cheapo" parallel port switcher here. Add a manual/auto toggle switch, a manual push button, and web controlled "button pusher" similar to the "IRmod", and you should be good to go. I'll modify one of these like this when I get time and post the info.
Sites with helpful info and similar setups here, here, here, and here.
Windows XP users note that the below in a batch file may be sufficient to make a button push (adjust the number of "a"s to get a stable button push) to switch the cams. This works on my XP pro machine, but not on my win98 machine. for win95/98, the serial port plug needs to be wired for a loopback arrangement for dos to initialize the port. Some info on making the loopback plug for win 95/98 here.
echo aaaaaaaaaaaaaaaaaaaaaaaaa >com1
The basic switcher pix:
Switcher based on Radio Shack 4017B chip (276-2417, $1.49).
Optical isolator made from Radio Shack MOC3010 (276-134, $1.99).
Basic switcher connected to power and serial port >> It works!!!.
Homebrew switcher schematic with info:
Above is a schematic of a somewhat "do-it-all" sequential switcher (I've added a combo of optional things to mix and match). "LED chasers" are usually based on the 4017B decade counting chip, so an LED chaser kit would be a good place to start. Things I've added to make it a sequential video/audio switcher: 1) The chaser would normally be powered by a 7-12V external battery/wallwart, but I've included the setup for getting power from the serial port via the diodes. Note that the port has to be open to get power, which requires developing a program that continously runs. If powering from the serial port, don't use the LEDs, as they will take more power than the serial port can provide. 2) Added a switch so a manual push button can be used inplace of the auto timer if desired. 3) Added a transistor around the push button to act as a switch. This is controlled by writing bytes to the serial port (so it can be computer/web controlled). 4) Added a resistor and capicator in parallel to ground between the pushbutton and the chip. This smooths out the bytes and "switch bounce" making for a single cam switch at a time. 5) Added a resistor/dip switch setup to the reset pin on the chip. This allows different numbers of cams to be used as desired. If you have 4 cams, connect the cam5 pin to the reset pin. This will make the chip go back to cam1 right after cam4. 6) added the resistor/transistor pairs to the output pins of the chip to control the video. When the LED lights, the transistor is on and video flows to the video out. 7) added a switch on the chip ground to select where the ground goes. If a capture card on a computer is being used, the chip ground needs to be connected to the video out line. If the video out is going to a tv, vcr or something besides the computer, then it can go to the serial port ground. If a computer is not involved (just using the Timer and push button), then the switch is not needed and just the ground to the battery/wallwart will do. Depending on if you build from scratch, or modify a chaser kit, you can add or delete as needed. I stopped tinkering with this sequential switcher when I found it is easier and more convient to use the parallel port for switching. As usual, YMMV!
