IC searching...

[alecacca]

i'm searching for an IC that control volume out with the variance of V that entry in the IC... do you know one?
thanks!  alex

[JimRayden]

i'm searching for an IC that control volume out with the variance of V that entry in the IC... do you know one?
thanks!  alex

I'd bet for a good LED-LDR arrangement. The input current will make an LDR change resistance. Then there should be an LED circuit where the LED lights up as the current goes down (Simple transistor arrangement?). Stick another LDR on that and voilà - an electronic non-scratching optical super hyper potentiometer. This needs some careful designing so it'd be linear enough and the whole resistance wouldn't vary much, but it's quite simple of a setup.

Nighty Night.

-----------
Jimbo

[bioroids]

You can use an OTA like the LM13600, LM13700 or CA3080, it will control the output with a varying current into one of the pins. You can do filters, phasers, tremolos and other stuff too.

Check out this page, it explains how to use them and some circuits with them:
http://www.geofex.com/Article_Folders/VCA%20Applications.pdf at Geofex

Luck

Miguel

[The Tone God]

Without more information it will be nearly impossible to make an accurate suggestion. What are you trying to do ? What are your input(s) and output(s) ?

Andrew

[alecacca]

very thanks for the good information! i'm am designing a tremolo where there are 3 tipe of oscillators:
- one, put to the Vout an intermittance of 5v, with speed regulator.
-one put to the Vout a shift from 0v to 5v
-one products, with a 14 stage couter like 4060, a current variable from 0v to 5v.

sorry for my bad english, i'm 14, i'm italian and i study english only from 4 years

[The Tone God]

Your english is better then my Italian.

If this is for a tremolo and you are going to be using those different control signals I would lean towards using an optocoupler as the safest option.

Oh and Welcome to the forum!

Andrew

[alecacca]

thanks!!!!! can you draw me... a simple application with the ldr? what resistance the ldr must do for have a decrase of volume?    thank you!        

[The Tone God]

thanks!!!!! can you draw me... a simple application with the ldr? what resistance the ldr must do for have a decrase of volume?    thank you!        

The CA Tremolo is a simple tremolo circuit using an LDR. You can find one here:

http://www.generalguitargadgets.com/index.php?option=content&task=view&id=88&Itemid=116

As for resistance range ideally you want a high dark resistance and a low as possible light resistance. It is difficult to find LDRs with that type of range so I personally think in this type circuit it is better have a low light resistance. You can then compensate for any signal drop with a gain stage.

Andrew

[alecacca]

can i put a vtlc that resistance 1m at dark and 5k at light? i put the ldr from the signal to ground..
for the ca tremolo... can i use this method? can you draw me a simple schem. to use it??? i'm not good in electronics...     thanks andrew! 

[smallbearelec]

As one of the other people noted, it depends on what you want to do. You say that you want to do a tremolo, and clearly you want some fairly sophisticated control of the modulating signal. The Anderton Trem that someone suggested looks like it gives a choice of triangle or square wave modulation, and the circuit is simple. If you want an oscillator that offers more control of the waveform, check out my Tremulous Bear in Projects at smallbearelec.com. Either way, you get a signal that is appropriate for driving the LED in a photocoupler assembly. Then you get to think about the modulator. This can be regular op-amps as in either of these designs, or someone suggested a VCA using the CA3080 or the 13600--also possible.

If you are not going to build a known design, do plan on doing a lot of breadboarding first.

Regards
SD