Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED (2024)

IMHO the photocells available to buy does not have tight tolerances as those used into vactrols or the like.
Also the response is generally too slow to certain applications: in an attempt to build a clone of Zvex wah probe the reaction delay time on the homemade photocoupler that links the antenna oscillator and the wah section was clearly marked.
In the other hand, those generic cells can do a reasonable job in opto compresors, trémolos etc.
Also these devices present memory effects: if you not use for several days a circuit that have a photocell the reaction differs from the same apparatus that was maintained in use more regularly.
I think that the available photoresistors can be used to control twilight lamps and things like that where the time of reaction and the illumination tolerances can be ignored.
One alternative if we need to couple a led and a photoressistive device is an optofet named H11F1. Personally I begin to experiment with conventional couplers (4N35, etc) and the results are "strange" most of the times that I plug this six pin IC's into the breadboard...

Cheers,
Jose

ppluis0 wrote:IMHO the photocells available to buy does not have tight tolerances as those used into vactrols or the like.
Also the response is generally too slow to certain applications: in an attempt to build a clone of Zvex wah probe the reaction delay time on the homemade photocoupler that links the antenna oscillator and the wah section was clearly marked.
In the other hand, those generic cells can do a reasonable job in opto compresors, trémolos etc.
Also these devices present memory effects: if you not use for several days a circuit that have a photocell the reaction differs from the same apparatus that was maintained in use more regularly.
I think that the available photoresistors can be used to control twilight lamps and things like that where the time of reaction and the illumination tolerances can be ignored.
One alternative if we need to couple a led and a photoressistive device is an optofet named H11F1. Personally I begin to experiment with conventional couplers (4N35, etc) and the results are "strange" most of the times that I plug this six pin IC's into the breadboard...

Cheers,
Jose

Thank you
I'm interested in specific devices:
1) Mu-Tron, its copy from EHX uses VTL5C3, but 3Leaf Audio uses a photoresistor and LED, both results work well in the demo (I did not have the ability to play on these devices).
2) Optical compressor, the situation is similar to DOD uses VTL5C4, Diamond VTL5C3, but EQD and Mad Professor make good devices with a photoresistor and LED.
3) Optical tremolo electric druid, the circuit points to VTL5C1, but it seems like some builders use the same photoconductor and LED.
I did not play on any of these devices, for this I'm not exactly sure how much the photoresistor and LED will be inferior to the optocouplers.

In general, optical effects are what I want to start to study and build, but for want of experience I want to understand whether it is worth trying to select a photoresistor and the LED or optocoupler will give better results.
I do not want to waste time and money on what will work worse, for this I am interested in someone else's experience.

The discouraging factor I experienced was the slow reaction time of commercial 5 mm LDR as mentioned previously. Perhaps some manufacturers can have models with faster slew times ?

BTW, here is a diagram about improve the response of photofets:

The complete explanation can be found here: https://www.edn.com/design/analog/43688 ... entiometer

Cheers,
Jose