Tremulus Lune LED/LDR

[jimmy54]

Hi fellas,

I bought a Vactec VTL5C2 from Banzai but when it arrived I found it to be a VTL5C4/2.  This has two legs on the LED side and three legs on the LDR side.  Can this be used as a replacement and if so does anyone know what legs should I use for the LDR side?

[QSQCaito]

I couldn't figure out if there's a difference in resistance, if it's the same i believe it could be used.

Here's the diagram of your Vactec, and Datasheet, just a clue to let the one who knows tell if it could be used, i think that if you connect legs 4with5 it could be used, but not sure.



Datasheet=http://www.pacer.co.uk/img/pdfs/vtl5c4-2.pdf

Hope it helps, bye bye

DAC

[Sweetalk]

http://www.pacer.co.uk/img/pdfs/vtl5c4-2.pdf

Here you got the datasheet of the VTL5C4/2 optocoupler, it seems to has a double LDR or so... Check it out!


Uuu QSQCaito just reply at the same time...

[jimmy54]

Thanks fellas, comparing the datasheets for the VTL5C2 against the VTL5C4/2 I note the following differences:

VTL5C2 Slope - 24, Dynamic Range - 69db, Dark resistance - 1Mohm, Temp coefficient - Low, Speed of Response - Slow, Light history effect - Small

VTL5C4/2 Slope - 8.3, Dynamic Range - 68db, Dark resistance - 400Mohm, Temp coefficient - High, Speed of Response - Fast, Light history effect - Large

There's a huge difference between the dark resistance, 1Mohm compared to 400Mohm.  This surely must have an effect within the circuit (whether it would be detrimental I don't know)

Can anyone in the know shed more light (pun unintended) on this?

[jimmy54]

Bump

[Floyd Pepper]

If it was me I'd socket the LED/LDR and try it with what I had. 

[jimmy54]

I would do if I a) had sockets and b) knew what legs of the LDR side to use.

[petemoore]

  Pin 4 to pin 3 is an LDR
  Pin 4 to pin 5 is another LDR
  Both LDR's resistances change with the brighness they're exposed to, so this could be used on a build that uses two different variable resistances from one point.
  So you can use 1/2 of the LDR's..say pin 4/5, or for possilbe lower minimum resistance [about 1/2] use both in parallel by adding pin 5 to pin 3 as 'one side'.
  Alternately if you wanted high max resistance seriesing the resistors should double it, to use both in parallel use pin 3 and 5 only.

[jimmy54]

Thanks Pete,

So I know what pins to use i.e. pin 4 and pin3/5 (joined).  This will give a dark resistance of 200Mohm (if the two 400Mohm LDR's are in parallel).  This dark resistance is still huge compared to the VTL5C2 which is 1Mohm.  Would this difference in dark resistance (1Mohm cf. 200Mohm) have an effect in the tremulus Lune circuit? 
Does the tremolo circuit work in this way - as the LED brightens the resistance of the LDR decreases and lets a signal through.  When the LED darkens the LDR's resistance goes up and the signal is attenuated.  Therefore both LDR's (VTL5C2 and VTL5C4/2) give a large resistance (albeit 1Mohm compared to 200Mohm) when dark.  As both of these resistances are very large will the difference when dark be negligible as far as the circuit goes?

Hope you understand this ramble.

Jimmy

[snufkin]

ive got an order coming in from banzi for the same part (the recomened one not that crasy 5 leged thing) i hope they dont send me any of them or ill cry 


newbie woes

[slacker]

Does the tremolo circuit work in this way - as the LED brightens the resistance of the LDR decreases and lets a signal through.  When the LED darkens the LDR's resistance goes up and the signal is attenuated.  Therefore both LDR's (VTL5C2 and VTL5C4/2) give a large resistance (albeit 1Mohm compared to 200Mohm) when dark.  As both of these resistances are very large will the difference when dark be negligible as far as the circuit goes?

Yeah thats how it works. I'd just try it in the circuit and see what happens, it can't damage anything.  You might find it works fine or the depth control might have enough adjustment to compensate for the extra resistance. If not you can just put a 1Mohm resistor in parallel with the LDR that will give it a maximum resistance of just less than 1Mohm, which is near enough what the VTL5C2 has.

[sovtek50]

You could have also contacted Banzai for replacing the VTL5C4/2 with the right one. They are very helpful, if they've made a mistake.