Fuzz Face bias voltage indicator (a la Smiley Face)

[axg20202]

I've been looking into adding a 'bias status indicator' to a new Fuzz Face build and came across the following (plus a few related threads in the archives here). Seems like a more practical solution than panel mounting an analogue voltmeter.

http://myweb.absa.co.za/g.landry/Smileyface.htm

Can someone give me a pointer on the correct LED to use? I'm only aware of two types of dual colour LEDs:

1) the kind with three legs that are 2 LEDs in one, sharing a common cathode or anode
2) the 'bi-colour' kind that show a different colour depending on which way round they are connected

Neither of these LED types seems right for the circuit shown at the link above??

Can someone help me here?

[chi_boy]

That indicator seems like a good idea.  Does it work?? 

I was thinking about something like this a while ago, but my thought was 5 3mm LED's in a row with each LED representing a 1/2 volt change and the one in the middle representing 4-1/2 volts.  Kind of like a short scale volt meter.  Of course my daydreams are bigger than my (nonexistant) electronics talent, so I never did anything. 

Thought about something like this too, but it looks too big:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXNK82&P=ML

Would have to remove the loading resistor, of course.

[chi_boy]

Or something like this:

http://www.ecelab.com/circuit-simple-led-voltmeter.htm

What would be ideal is LED's that work like the LED's on a tuner.  A green one in the middle for 4.5v and 2 reds on either side for flat or sharp, oe low or high.

Ah, never mind, it's time to practice. 

[axg20202]

Yeah, I had considered a small array of LEDs but this isn't really necessary and creates enclosure construction hassle. I can also get hold of a simple panel-mounted analogue voltmeter, but it's a big item to add to a small enclosure and I don't fancy my chances of making a nice clean square hole in the face of the pedal anyway.

My preference is for a single two-colour LED, showing red when the Q2 collector is below -4.5 volts, turning green when it hits -4.5 volts or above. The LED circuit I linked to in my original post seems to fit the bill, if only I can determine what type of LED I need. The instructions are quite clear apart from that most critical component in the circuit! 

Anyone?

[axg20202]

I e-mailed Guido about his Smiley Face circuit and he confirmed that the LED in the bias indicator is indeed a bi-colour LED (the type with 2 anti-parallel diodes) which lights a different colour depending on orientation/polarity in the circuit. I'm going to go ahead and build it so see for myself. I'll post my PCB layout for the bias LED circuit if I'm happy with it (and Guido doesn't mind).

[Tuemmueh]

Thanks for pointing me to the circuit and the information about the led (and thanks to Guido for the circuit for sure ... )

[Gus]

Joe G IIRC Did you have a car meter mounted in a Fuzz?

[gigimarga]

take a look here...it's a post of mine on a romania electronic forum...i test what they said to me and it worked: http://www.elforum.ro/viewtopic.php?f=66&t=23459...

[axg20202]

take a look here...it's a post of mine on a romania electronic forum...i test what they said to me and it worked: http://www.elforum.ro/viewtopic.php?f=66&t=23459...

I would, but it's all 'in foreign' (joke). Care to translate?

[gigimarga]

Sorry, but i can translate in only next week because i have a lot to work
The only problem is that it consumes over 15mA...

[Dragonfly]

Joe G IIRC Did you have a car meter mounted in a Fuzz?

yep...he did....

Nitroburner

the schematic is in the gallery

[Ry]

Joe G IIRC Did you have a car meter mounted in a Fuzz?

I have wanted to do this since I saw the Nitroburner.  I wonder how much current the meter draws.  Time for some research...

[Dragonfly]

Joe G IIRC Did you have a car meter mounted in a Fuzz?

I have wanted to do this since I saw the Nitroburner.  I wonder how much current the meter draws.  Time for some research...

Beavis / Dano added a meter to monitor battery "sag"...

http://www.beavisaudio.com/Projects/DBS/

[Renegadrian]

http://g.landry.myweb.absamail.co.za/Smileyface.htm

seems very interesting...

[axg20202]

Man this thread is old. Anyway, that schemo is exactly what I used to fashion a PCB for the reference circuit. I can confirm that it works like a charm - a simple circuit to give you a visual indication of bias setting.