alalog VU meter

[davidbball13]

i want to make a VU meter i think i can use the bargraph display driver any ideas
i dont really have something in mind i was hoping that you guys knew somethings on the topic

david d


new fav. band scary kids scaring kids

 

[audioguru]

The LM3914 is a linear voltmeter and makes a poor VU meter.

There is the LM3916 IC which drives up to 10 LEDs in various sized steps as a VU meter.

There is the LM3915 which also drives up to 10 LEDs in doubling or halving of power steps as a VU meter.

The datasheet for the LM3915 shows a few "peak detector" circuits that hold the peak reading for a moment which is long enough for it to be seen. Without a peak detector then a bargraph is a blur and a moving dot is a dim blur.

I have a Sound Level Indicator project. It uses an LM3915 driving 20 bright LEDs in 10 steps that have a dimming pot. It has a peak detector circuit. I added 20dB worth of automatic gain control so that it displays a pin dropped on the floor of the next room if there is no other sounds and if I hold my breath, and it clearly shows loud music. Therefore its range in levels is 50dB.
It has a rechargeable 9V battery (actually 7.2V) plus a wall-wart power supply.
https://www.electronics-lab.com/projects/motor_light/009/index.html

 

[stevez]

David - I have a bunch of small VU meters that appear to behave as if they have a logarithmic response built in. I am old enough to remember - but can't for some reason - if I am correct that many VU meters were constructed this way - so that that an otherwise linear signal does not need to be conditioned to get the log (I think that's what's needed) response. If I am correct all you will need to do is procure a VU meter and consider how you might adapt the available input to the range of the meter.

There are a number of ways to take a surplus or discarded meter and determine it's characteristics. You ought to be able to find that via google or in electronics references.