Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

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Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

Postby POTL » 27 Jul 2018, 12:07

Hello
I want to know if it makes sense to change the ready-made solutions in the form of VTL5C2 / VTL5C3 to photocell + LED.
The replacement looks cheaper and more affordable in the store, but I am confused that there are no photocell that fit within the technical specifications of the optocouplers.
However, I often saw photocell + LED from boutique manufacturers like EQD (Warden), Mad Professor (Forest Green), 3Leaf Audio (Proton / Wonderlove) etc.
At the same time, large manufacturers produce their products with optocouplers EHX (Q-Tron), DOD (280 Compressor), Diamond (Compressor).
I have doubts whether it makes sense to save time and money and put a photocell + LED or better to put a ready optocoupler?
Will there be a marked difference in the operation of optical effects or the difference in the extreme characteristics of the parameters do not play a role?
POTL
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Re: Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

Postby ppluis0 » 27 Jul 2018, 21:26

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... :roll:

Cheers,
Jose

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POTL (27 Jul 2018, 22:31)
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Re: Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

Postby POTL » 27 Jul 2018, 22:38

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... :roll:

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.
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Re: Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

Postby Optical » 28 Jul 2018, 00:17

You might want to look at optofets, they have much higher performance than LDRs - much lower on resistance and high off resistance. There will be some fine tuning to get a linear sweep of useable resistance inbetween, but it is possible
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Re: Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

Postby ppluis0 » 29 Jul 2018, 06:09

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:
Image

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

Cheers,
Jose
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Re: Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

Postby POTL » 29 Jul 2018, 22:25

Thank you
h11f3m costs in my country 5.5 dollars it is almost equal to the price of vtl5c3
I came to the conclusion that it's easier to order the right component and 100% to get the desired result.
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