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Topic: Simple LED meter? (Read 2 times) previous topic - next topic


Can someone help me out? :)

I want to make a simple LED meter (VU?) that comprises of 5 LEDs, 2 green, 2 yellow, and 1 red, voltages at 2.2 and 2.3 volts.
I need to know what resistor values i would need. This circuit does not use any chips or transistors (i have seen the kit but no schematic)
all it uses are LEDs, resistors, and a diode, a capacitor too.
Its use wil be for adding into some speakers, or on the front panel of a pc to show sound level, and I really want it simple as possible, no chips or transistors (I cant get them easily), resistors and LED's I can get easily tho. and the kit i have seen online only uses them and a diode and cap.

Can someone throw up a diagram and list suitable resistors for such a thing please? :) i am still learning this stuff and this will help.

thnx ;)
B-dui in creation.


anyone? :o I'm still searching but haven't found anything yet :(

realy could do with the help, I know its prolly simple but thats only if you know how..
B-dui in creation.


I think the problem is that no one can see where the Arduino fits in.

Also what voltage will be driving this? Is it straight from the speaker output of an audio amplifier or is it on the input side. Asking for something without transistors in it limits you to what can be achieved. You need a largish voltage that is probably not available on your system without amplification.


this is the bar sport section ;) ie: non arduino goes.

it will probably be driven direct from soundcard/mp3 player. I could probably drop the voltage a bit b4 it is need be, i just want to try it out so i an understand more, like i said i have seen the kit but they give no info about it and the image was too small to se the resistor values.
B-dui in creation.


Your problem will not be too much voltage but too little.

OK it's a bit tricky without a diagram but attach a diode Anode to your sound source, connect a resistor (510R or so) from the cathode to a low power LED and the other end to ground. Now repeat this arrangement and hang it not from the sound source but from the cathode of the first diode. Repeat again connecting it to the cathode of the second diode.

So this looks like a string of diodes in serese from each junction of cathode and anode you hang a resistor and LED to earth. If the audio signal is over 0.7V the first LED will light, if its over 1.4V the first two will light, if it's over 2.1V the first three will light and so on. Do use low power LEDs the sort that will only draw about 2mA. Also the circuit might distort your audio signal a bit.

Can you follow this?

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