Using a LM3916 metering IC for gate trigger for PIC

Discussion in 'The Projects Forum' started by nnxen, Sep 9, 2014.

  1. nnxen

    Thread Starter New Member

    Dec 22, 2012

    I'm working on a project based around a PIC microcontroller to do some audio sampling. One thing I'd like to incorporate is a gate threshold. Due to several reasons, I'd like to do this in hardware rather than in code on the PIC itself. I was thinking of using something such as the LM3916 to meter the audio input and use one of the outputs to drive an input pin on the PIC to tell it when the gate should be considered open. I have a few questions:

    - I'm running the entire thing from a 5vdc single-supply and the audio input is biased by 2.5vdc by a prior pre-amp stage. Do I need to decouple the DC before sending it to the LM3916?

    - I'd like this gate threshold to be adjustable, which I should be able to do by adjusting the sensitivity on the metering IC - I assume Figure 26 of the linked datasheet would achieve this, omitting R4 and R5?

    - Page 16 of the linked datasheet states that reference voltage has some effect on LED intensity, but since it will be driving an input of the microcontroller instead, am I right in thinking this current change shouldn't be an issue?

    Any help is much appreciated! It's all a bit confusing for a newbie! Any alternative suggestions are also very welcome.
    Last edited: Sep 9, 2014
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    hi nn,
    Thats a complicated way of getting what you want, if using only one LM3916 output.

    Look at the LM393 dual comparator IC