Quote Originally Posted by sanking View Post
Just for the record, the Wejex that I have has an exposure duration of 2.5 seconds.

Sandy

Thanks for the info. Can you post a picture of your unit? I wonder how else it is different from the one I have. Mine buzzes for about 2 seconds but the shutter is only open for one second. I know the current model they show on the Tobias web site is smaller than mine, and I suspect the inner workings may not be the same (http://ourworld.compuserve.com/homep.../prodother.htm)

I really like the Wejex design and in fact was looking into parts availablility to do a little article about making a sensitometer based on some of the existing designs.

Timing with the Wejex is very consistent because it uses a Synchronous motor in which the speed is dependent on the Hertz of the energy source, not the voltage. So it runs at the same speed at 117V and 121V etc. As long as the Hertz is the same (60Hz in the USA).

I found a source for a 60 RPM synchronous motor. With a shutter shaped like a semicircle (180 degrees) it would produce an exposure time of 1/2 second. Then all you would need would be a microswitch, bulb and box, diffusor, stepwedge, etc.

The other way to go would be to use LEDS and something like the 555 IC timing chip and battery power and base it on the X-rite style (though, with 'white' LEDs).

The third way would be to copy the EG&G and just get a used standard photoflash with a Manual setting, and put this into a box.