vactrol switching

[dscottguitars]

Hi,  I am replacing my relay switches with vactrol switches, a suggestion made on an earlier post about a year ago.  Can I use the same power supply that I currently have for my relays?  I have the 5v one that is sold on this site.  I thought I read somewhere that only 2v is needed.  If so, can I switch out the 5v regulator for a 2v one?


I currently use 2 of the double pole relays and I'm planning on using 8 vactrols to make that same switching diagram.  There are pics of the current setup and the vactrol setup.  (the drawing of the vactrols may not be 'correct', but it's just to represent what I'm doing)


  Thanks...

[PRR]

They are LEDs. The exact voltage of an LED is not known and not critical. You need a reasonable *current* through the LED. The simple way to get this is a higher voltage and a series resistor to set the current.

Nominal current for Vactrols is 16mA. The LED will drop 1.5V to 2.0V. Start with 5V (which you already got). You need to "lose" 3V to 3.5V. Take worst-case 3.5V and divide by 16mA which is 0.016Amps. I get 218.75 Ohms. Round-up to 220 ohms. Use 220 Ohms in series with each LED and feed it 5V.

[dscottguitars]

Thanks, that sounds easy enough...

[dscottguitars]

I finally got all the things I need to do this and I'm wondering about my layout/diagram for mounting these.  I want to put 4 together (see the + on the drawing) so I don't have so many wires.  With your suggestion, would I then consider them in parallel and use one 56 ohm resistor?

[sluckey]

I finally got all the things I need to do this and I'm wondering about my layout/diagram for mounting these.  I want to put 4 together (see the + on the drawing) so I don't have so many wires.  With your suggestion, would I then consider them in parallel and use one 56 ohm resistor?

Will all 4 be switched on and off at the same time? If so, use one resistor.

[dscottguitars]

Yes, but I'll have to modify my setup a bit.  Thanks for that tip.

[dscottguitars]

Well this is not working.  I cannot get a voltage drop.  I first tried a 51ohm resistor and the voltage reads 4.93v.  I tried a 150 ohm and no change.  I hooked it in series with the switches.  What am I doing wrong?


Also, wouldn't it be easier if I just had a 2v voltage regulator?

[sluckey]

Well this is not working.  I cannot get a voltage drop.  I first tried a 51ohm resistor and the voltage reads 4.93v.  I tried a 150 ohm and no change.  I hooked it in series with the switches.  What am I doing wrong?

You gotta have the switch, resistor and LED all connected in series across the power supply. Then you'll have current flow and voltage drops.

Also, wouldn't it be easier if I just had a 2v voltage regulator?

No. You must have a resistor in series with the LED to act as a CURRENT LIMITER. That's as simple as it gets.

[dscottguitars]

Hmmm, not sure what I had wrong, must have been the switch as I took out the led indicator light, but now I can't figure out how to get the light working.  Do you have any schematics for footswitch wiring?


I now have 1.6v on the vactrols.  I'm looking for a different resistor unless you think that's okay.


Thanks...

[sluckey]

Hmmm, not sure what I had wrong, must have been the switch as I took out the led indicator light, but now I can't figure out how to get the light working.  Do you have any schematics for footswitch wiring?

Show us a schematic for what you think you are doing. Sounds like you are trying to turn on an optoisolator and simultaneously turn on a separate LED. You know there is a LED inside the Vactrol??? Get the vactrol working first then add the external LED.

[dscottguitars]

Yes, I do know the vactrols are LED's.  Is that my problem?

Here is a drawing of what I have now.  I tried adding a red LED to each of the foot switches and got really screwed up results:


Channel two (2) was very bright and measured 3.85v on the center lug and over 2v on the line going back to the amp


Channel one (1) was still 1.61v when switched on (no LED for this one)


Mid boost (3) was 1.61v but the LED would not work


I tried using a 1000 ohm resistor in series with the LED's and mid boost LED worked but voltage was 1.47v while the channel switch dropped to 1.6v but still 3.85v on the center lug.  (this is really confusing me and aggravating)


I can add a battery for the red LED's but would prefer not to. 


I first had one 51 ohm resistor in front of all the vactrols with the same voltage so I thought maybe adding separate ones would change things but no luck.

[MakerDP]

Hi,  I am replacing my relay switches with vactrol switches, a suggestion made on an earlier post about a year ago. 

Can I ask why the suggestion was made? i am about to do channel switching for the first time and I was waffling back-and-forth between vactrol, relay and JFET switching. I finally decided on relay using a dedicated 6.3V pcb-mount transformer for power and ordered the parts this weekend.

A link to the original post is OK if you don't feel like rehashing the whole post.

Thanks!

[dscottguitars]

The way I tried to switch two channels, one clean and one high gain with only one set of controls brought the two signals too close to each other in the relays and caused some feedback.  Also, I had some vibration noise that would cause a horrible sound when the amp head was on the speaker but not next to it, and the suggestion was maybe the relays were picking up that vibration and causing the noise.  With the vactrols I can wire it like I want to and will then know about the vibration noise.

[MakerDP]

Very cool. Thanks for that.