Need help with photocell stats

[gmontag451]

I'm trying to choose a replacement photocell, and I'm not sure how to convert the old photocell's ratings:

1: The old cell's resistance is given at 2ft candles. I believe 2ft-candles ≈ 21 lumen, but how do I convert it to 10 lumen? Maybe (R ÷ 2.1)?

2: The old cell's Illuminated Resistance is 1.5k. But modern photocells give Illuminated Resistance as a range, like "0.5 ~ 17kOhms". How do I choose an appropriate photocell if I only have a single value?

3: How can I measure the voltage applied to the old photocell with a multimeter?

Any help would be greatly appreciated!
-Michael


The old photocell's datasheet gives the following:
Illuminated resistance 1.5k @ 2ft-candles
Min dark resistance 400k @ 2ft-candles
Max voltage 250V

 

[PETERDECO]

Welcome to the forum. I believe you are referring to an LDR (light dependent resistor). A couple of questions: what is the purpose/function of this part? Do you have a part number for the original? My LDR of choice is a 5528. It has a wide swing of resistance from 8-20K in light to a minimum of 1M dark. I have successfully used this one to replace damaged ones with unknown spec's.

 

[gmontag451]

Hi Peter, thank for responding and for the 5528 suggestion!
The part in question is a discontinued Clairex CL5M4 (datasheet at bottom). The circuit is used to create a flicker flame effect in an incandescent light (video). The CL5M4 is contained inside a black canister with 5 LEDs which turn on and off at different intervals, creating a random resistance. A couple of potentiometers control the min and max brightness.

I'm sure many replacement parts will work just fine, but I don't really know where to begin looking since the ratings are listed differently between the datasheet and websites like DigiKey/Mouser/etc. (Also I'm sure there are much better ways to accomplish this effect today, but the board in question has a lot of nostalgia for me!)

 

[Harald Kapp]

As @PETERDECO said: go ahead, buy maybe a handful of different LDRs that fit into this position. You have two potentiometers to adjust the circuit and match the behavior to the LDR:

LDRs are not very precise components, their parameters can vary widely. And with the two potentiometers I'm confiident you can adjust the behavior of the circuit to your liking.

 

[gmontag451]

Thanks for the advice! I kind of expected this would be the case, but I didn't have the experience with these to take that leap. Glad you guys were here! I've posted the same in 5 different forums and received no responses anywhere else, so thank you.