Small Stone Rate LED - LED blinks the wrong way!

[drummer4gc]

Hey everyone,

I've been working for awhile on designing a good way to get an LED to pulse with the rate of phasing in a Small Stone. I did a lot of reading, but could only get the LED to blink on and off, or pulse but not turn off completely, so the effect was weak. Using a ton of information I've found here and a biasing idea of my own, I came up with this:



It looks great - pulses smoothly, LED turns all the way on and off. The biasing is probably strange and comes from me not knowing a whole lot about what I'm doing.

Here is the issue though - it pulses 180 degrees out of phase with....the phaser. That is, the LED turns off as the phaser hits its high pitched peak, and it turns on as the phaser comes down to its low peak. Is there a way to reverse this?

Thanks!

[mth5044]

I can't see the image you posted due to a work computer, but you could try running an inverting opamp section before the LED to invert the LFO signal.

[slacker]

You could try a PNP transistor, flip it the other way round so the emitter goes to the 1k resistor. I'm not sure if you'll be able to bias it how you want though.

[armdnrdy]

I believe that this would work as well. You might have to fiddle with some of the values.

When the base of Q1 is high, the base of Q2 is low.

[armdnrdy]

Now that I'm thinking about this...

I don't see why you can't connect the LED anode to Q1 collector-R2 junction and the cathode to ground and delete Q2.

That config. would invert the signal from what it is at the base of Q1. (LFO signal)

Something like this:

[drummer4gc]

PNP was the ticket. No voltage divider, LED between 9v and emitter, 1k to ground, and that's it. Thanks for all the suggestions!

[mickeybellinello]

Here I am!

Which Transistor did you use?

[deadastronaut]

3906?

[drummer4gc]

3906?

Probably. Maybe 2n5087. I don't think it's too critical.

[BetterOffShred]

Did this to my Whetstone clone (which is based off the small stone) with a 3906, works great.  Maybe just a tad Square-ish swell/fade but totally serviceable.

Thanks guys

[mickeybellinello]

thanks to all for replies!

[deadastronaut]

on my faze filter i used a 3904 and did it this way....see pdf.

https://deadastronaut.wixsite.com/effects/faze-filter

[mickeybellinello]

on my faze filter i used a 3904 and did it this way....see pdf.

https://deadastronaut.wixsite.com/effects/faze-filter

Thanks, I'll take a look immediately

[mickeybellinello]

on my faze filter i used a 3904 and did it this way....see pdf.

https://deadastronaut.wixsite.com/effects/faze-filter

Finally I made a try and it works nicely!!!
I only added a 470K resistor between "pin7" and the transistor to get a best results in slow setting.
Thanks Again!

[deadastronaut]

cool, glad it works.