VACTEC VTL5C3/2 VACTROL

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What were this use in ??

Take a look at his datasheet. They were one of the versions of opto isolators. These had CdS photoconductive cells with LEDs. (earlier generations used filament lamps with CdS cells). The datasheet shows some interesting (at least from a historical perspective) applications.

I used one long ago for an audio gate and AGC. CdS cells were not without their problems; memory effects, voltage dependence and speed of response. At the time though it was the best technology for many applications. Cadmium (Cd) is now on the list of banned RoHS materials, so has fallen out of favor.

I remember looking at a really old street light photocell. It was a huge CdS cell directly driving the heater of a bimetal switch that controlled the street light. Very simple though not the most energy efficient. By contrast, the new photo switches installed on our street will shut off the street light whenever there is a flash of lightning - something that the old school ones didn't do. Then, of course, it takes 3-5 minutes for the lamp to sufficiently cool that it can re-strike and warm up to full brightness.

PLONK

-- You can't have a sense of humor, if you have no sense.

I'm familiar with these and we used them in a test set I designed around =

I probably have a few in my junk piles. No use for them now.

Have you tried eBay?

Or, see if you can come up with a unique design that uses them, and sell = the=20 parts as a kit.

Good luck,

Paul

Some of the antenna guys use Vactrols to install variable terminations on beverage and Flag/Pennant antennas. The problem with that particular Vactrol is the minimum ON resistance is to high. A good termination range is 350 ohms to 1100 ohms. I'm not sure about the photocell pins 3, 4, and 5.

Would pins 3, 4 be half of the pins 3, 5 resistance?

If yes, then the graph shows 1,050 ohms on resistance, half of that would be 525 ohms, If you parallel 525 ohms//1,050 ohms you get 350 ohms. (that's putting a fixed 1,050 resistor across pins 3 and 4 of the photocell.) Then if you adjust the photocell current to zero, you have 1 Meg//1050 or almost 1050 ohms. That's pretty close, and assumes pin 3,4 is half the photocell resistance.

What the ON resistance be if you shorted pins 3 and 5 and measured to pin 4? Mikek

No, you're not. See below.

No, it isn't. Check the spec sheet first next time.

Lord Valve