VTL5C4/2

[widebit]

how i can make my own VTL5C4/2 ??

there is no VTL5C4/2 in europe, so i have to do it my self, but it's not so easy because i dont know values and effects from the original VTL5C4/2.

[puretube]

http://www.pacer.co.uk/img/pdfs/vtl5c4-2.pdf
http://optoelectronics.perkinelmer.com/catalog/Category.aspx?CategoryName=VTL5C+Series
http://www.smallbearelec.com/Ordering/Photo.htm

[DiyFreaque]

Sometimes 'rolling your own' can result in 'happy accidents' - you may find a combo of LDR and LED that you like better.  For quickest results, I'd say follow Puretube's links.  

But if you (or anyone else is interested) here's some info on selecting the components of an optoisolator (methods I've used before).    

You can build something close to a VTL5C4/2 using one LED and two light detecting resistors (LDR's).  You would need to rig it so that the LED shines on both LDR's.  The five legs of the improvised VTL5C4/2 would consist of:

(1) The anode of the LED
(2) The cathode of the LED
(3) One leg of LDR #1
(4) The other leg of LDR #1 connected to a leg of LDR #2
(5) The remaining 'free' leg of LDR #2

Normally, people use heatshrink or some kind of potting solution to fashion optoisolators.  

The real trick, however, is finding the right combination of LDR's and LED to mimic a VTL5C4/2's characteristics.

To begin with, here is a link to the VTL5C4/2 datasheet:

http://optoelectronics.perkinelmer.com/content/Datasheets/vtl5c4-2.pdf

This may help you somewhat in your selection process.

The most important factors that determine the characteristics of an optoisolator are:

1.  Light Resistance (the lowest resistance when the LED is on)

2.  LED current needed to reach the light resistance.

3.  Dark Resistance (the highest resistance when the LED is off)

4.  The time it takes an optoisolator to go from dark resistance to light resistance

5.  The time it takes an optoisolator to go from light resistance to dark resistance

Items 1, 2 and 3 should be easy to figure out with a DMM.  Items four and five are not so easy, unless you have an oscilloscope, function generator and a test circuit set up on a breadboard or perfboard.  Items 4 and 5, however are *very* important and will impact the performance of the circuit if the optoisolator is being used in things such as compressors, filters, VCA's, etc, where it has to respond to (or in some cases, *slew*)fast control transients.   Many circuits depend on these characteristics.  

However, without the mentioned test equipment, here is something you can do:  

(1) Buy a bunch of LDR's, and a bunch of LED's

(2) Get a 'ballpark' figure on points 1 and 3 (just measure the resistance when the LDR is covered or exposed to fairly bright light) and select the one's that come close to the figures in the datasheet.

(3) Get a film cannister (those little black containers that photographic film comes in) and punch 5 *tiny* holes in the lid of the cannister.  

(4) Mount the LED and two LDR's on the inside of the lid, with the LDR's pointed at the LED as closely as possible.  Run the legs out through the five holes.  Snap the lid back on the film cannister.

(5).  You now have a rather large and bulky optoisolator.  Get a breadboard and mount this contraption on it.  

(6).  From the points of your circuit that connect to the VTL5C4, run jumper wires to the appropriate legs of the contraption.

(7).  Listen to how it sounds/works.  This way, you can mix and match LED's and LDR's until you get something you're happy with.

(.  "Hand Roll" your custom VTL5C4/2 using the components that sounded best to your ears.

Cheers,
Scott

[Anonymous]

Check out www.modezero.com
On the What's New Page > scroll down to
(060403-0023)  Added a new page for the Custom Analog Electronics Infinitephase.

The #6 & #7 pictures (scroll down) show 4 LED's in the center of 8 Photo-Cells on a phase shifter circuit board.

It is in what I would assume to be a light-free enclosure since they don't try to encapulate the assembly in anything.

Also at www.geofex.com there's an article on building a substitute CLM-6000 (discontinued) optoisolator.

This should give you some ideas.

[DiyFreaque]

Hey, that reminds me!

A friend of mine over in Japan, Motohiko Takeda built a phase shifter I think based on that same model, or at least inspired by that Modezero account.   At the time I recall him describing it sort of like  "LDR's sitting around the campfire".

He's actually put a lot of fairly extensive analysis into rolling your own Vactrols, which can be found here:

http://www.aleph.co.jp/~takeda/radio/phaser/indexE.html

Pretty good stuff, if you're into optoisolators (and I am!).

Cheers,
Scott