Guitar Level Meter - Opamps

Discussion in 'General Electronics Chat' started by zxzqz, Sep 12, 2006.

  1. zxzqz

    Thread Starter New Member

    Sep 12, 2006
    2
    0
    Hi,

    Im considering trying to make a lever meter for my electric guitar signal, despite being very new to electronics. Very rough idea is to send the signal to a buffer amplifier, then use a load of comparators referenced to a resistor ladder to power leds so they light up in sequence as the signal gets stronger. Would prob also need rectification at some point to get to dc. Is this a reasonable way to go about it or not?

    Anyway I found a lm741 opamp at home so decided to play around. Using 9v supply and a potential divider to provide the signal, I managed to get it to voltage follow by directly feeding back but only down to about 1.5-2v, the output would not go below that. I think the range I need to be looking at is 0 to 1v, maybe even 0 to 0.5v. Is this something to do with offsetting (or is this just compensating for inaccuracy in the opamp and of no use to me), or do I need an opamp that goes down to ground so I can get down to the range I need? If so what would be suitable? The LM358N perhaps?

    Appreciate any help!
    Thanks.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    There are a number of circuits on the Internet. Below is a link to one that uses an LM3915. I'm sure that other members can point you to other circuits that you can choose to use.

    http://www.free-electronic-circuits.com/circuits/audio-level-meter.html

    Take a look at this one and any other offerings that come along and see which one looks best suited to your project.

    Once you have one in mind, you can then come back to the AAC forum with questions on specific details of the circuits operation.

    hgmjr
     
  3. zxzqz

    Thread Starter New Member

    Sep 12, 2006
    2
    0
    Thanks for your reply.

    I originally got the idea for a meter by stumbling across the lm3914/5/6 ics. After spending ages looking at the datasheets, I thought about trying to do it myself. Reasons being: To learn about opamps, buffers, comparators. Also because I need to control 13 leds which would need 2 ics, which would cost around £9 for 2 lm3914's (cant find the other 2).

    If you could tell me whether a different opamp is what i need for the buffer stage, and if my general idea is ok that would give me something to experiment with. Also if anyone has a circuit diagram for what I'm trying to do, with a load of opamps, then I could try and understand that.

    Would rather try understand it than just copy a circuit if at all possible, though I guess I will have to resort to the ics if its gonna be too difficult.


    Cheers!
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
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