Fetish for Panel Meters, any ideas?

Started by dano12, February 06, 2006, 12:18:41 PM

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dano12

I'm new to building and modding pedals, but am slowly getting the hang of it, so this may seem like a strange question.

I'm working on a treble booster that feeds into a Fuzzface clone, all in one enclosure. Because I have a fetish for analog panel meters, I'd like to work one or two into the design. I.e. find a few interesting places in the circuit to tap a meter in.

I guess meters have an inherent resistance? Would that cause problems with the circuit itself? Or does this even sound feasible?

Any help or links would be greatly appreciated.
-dano

BrianJ

You would definitely want to isolate any meter sonically from the rest of the circuit.  Im not too familiar with driving Darsonval meters- Depending on the size of you signal it might be possible. You might try connecting an op amp buffer (unity gain configuration) to the collector of you last gain stage (before the volume pot).  Depending on the dc collector voltage, you may need to capacitavely couple the op amp and rebias it.  The output of the opamp could drive the meter through a cap. The output of the opamp could also drive an LED through a resistor to ground.  If you play with the value of the resistor, you may be able to get the LED to light up a bit when you play hard.  All of this stuff will draw current and shorten battery life.   If you're crazy, you could use a 3 threshold window comparator circuit (at least 4 opamps, several resistors, and some more mA) to drive a 3 color LED.  I put something like that together a while back for a mic pre, but using a single 9v supply would make it trickier. 

I hope I didn't discourage you,
Brian

petemoore

  Do you have a meter in mind, I'm curious about the resistance between it's leads.
Convention creates following, following creates convention.

dano12

Sorry, should have been a bit more specific. I'm looking at analog meters (DC and Milliamps). Not that they would provide truly useful value, but would simply look too cool :)

The entire box will be driven of a 9v wall wart, so battery drain isn't an issue.

dano12

Quote from: BrianJ on February 06, 2006, 01:40:48 PM
You would definitely want to isolate any meter sonically from the rest of the circuit.  Im not too familiar with driving Darsonval meters- Depending on the size of you signal it might be possible. You might try connecting an op amp buffer (unity gain configuration) to the collector of you last gain stage (before the volume pot).  Depending on the dc collector voltage, you may need to capacitavely couple the op amp and rebias it.  The output of the opamp could drive the meter through a cap. The output of the opamp could also drive an LED through a resistor to ground.  If you play with the value of the resistor, you may be able to get the LED to light up a bit when you play hard.  All of this stuff will draw current and shorten battery life.   If you're crazy, you could use a 3 threshold window comparator circuit (at least 4 opamps, several resistors, and some more mA) to drive a 3 color LED.  I put something like that together a while back for a mic pre, but using a single 9v supply would make it trickier. 

I hope I didn't discourage you,
Brian

Holy toledo! I think I'll be able to understand your response after another year or two of learning about my new hobby :) Not discouraging at all, but I'm heading off to Google now to get a handle on your helpful response. (I'm thinking about analog meters and the box will only be powered by DC wall wart, so that may simplify it a bit for me). Thanks much.

Dingleberry Electronics

PIMP MY PEDAL!

I once found panelmeters from a local electronics store season sale for very cheap. 1€/meter... I had to buy all of them what was left. (12)
They were east-germanian made in very large(about 8cmx8cmx8cm)  bakelite housing with real glass cover. They look really vintage
comparing to the year they were made (1990 stamped on the rearplate). They are voltmeters with 0-6V range so I thought that it would be
pretty easy to use them in a some twisted effects design. I've been using them now in a various projects. First one was MUTRON III, which I got
the main idea from. The way I've been using them is very simple. I took the led driver part of the mutron schematic because of its simplicity,
(one op-amp design), made stipboard layout of it and used it to drive the voltmeter. I was really amazed that it was that easy.
Just adjusted the trimmer to get the widest sweep range and voilá! Meter is bouncing up and down depending on the signal amplitude.
It is very easy to add in nearly any effect. For example n MUTRON III there is only buffer stage before the signal is spitted in two with two caps.
One going to main audio path and one going to drive two leds(or the led side of an optoisolator), which are varying the resistance of two LDR:s(in the signal path)...
In MUTRON III I used 12vdc but I've used the same configuration with 9vdc without any problems.
Really easy to make an unique design for unique sounding effects. I looks tally cool to see when the meter is bouncing in sync with the filter or any effect you like.
Thats what I call pimpin'.

toneman

LM3914s & LM3915s are LED bargraph drivers.
Certainly would "look cool"   8)
Might eat a little more batt pwr...  :-\
Otherwise, just use a simple opamp buffer to drive either the 39xx or the meter.
There are lots of webpages on audio metering/bargraph.
afn
T
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H S

Hmmm, a needle meter must be an inductive load with pushback from a spring-loaded physical system (the needle).  How would it do as a speaker simulator? :icon_question:

Peter Snow

Hi Dano,

You may want to try one of these.  At $0.79 each you can't go wrong.  Looks cool too!

http://www.goldmine-elec-products.com/prodinfo.asp?number=G3301&variation=&aitem=57&mitem=181

Cheers,

Peter
Remember - A closed mouth gathers no foot.

BrianJ

If you were to use a dbv (decibels-in-voltage) meter, it might be right up you're ally for a fuzz face output meter.  The meter would read a scale of -20db to +3 db.  In "dbv" 1 volt is 0db.  If the distorted output of the fuzz face is around one volt, the meter would be responding properly. It would, ironically, be a real meter.

Go for it.

dano12

Quote from: BrianJ on February 07, 2006, 12:21:52 AM
If you were to use a dbv (decibels-in-voltage) meter, it might be right up you're ally for a fuzz face output meter.  The meter would read a scale of -20db to +3 db.  In "dbv" 1 volt is 0db.  If the distorted output of the fuzz face is around one volt, the meter would be responding properly. It would, ironically, be a real meter.

Go for it.

That sounds like a very cool idea. Ok, now for the noobie question--are dbv meters available stock, or do I have to build some kind of circuit to create one out of some other type of analog meter? I googled this but couldn't seem to nail it down. Thanks much!

dano12

Quote from: Peter Snow on February 06, 2006, 10:34:17 PM
Hi Dano,

You may want to try one of these.  At $0.79 each you can't go wrong.  Looks cool too!

http://www.goldmine-elec-products.com/prodinfo.asp?number=G3301&variation=&aitem=57&mitem=181

Cheers,

Peter

Wow, very old school and cool looking too! The price is right. Couldn't find specs on what type of input it excpects but I'll do some digging. Thanks!