Hello forum, don't know if I'm in the right place, I'm audio engineer and just putting final touches in my personal recording studio. 90 percent of all the gear,furniture,cabling, etc. is all custom made and very unique both in design and tonal quality. 2 of those pieces are now in final stages of design and as we add features we came to the conclusion that it could greatly benefited form some form of metering. I'm an old school engineer that grew up in the analog world and back in the days I grew up loving the look of the ppm plasma metering system. For these two pieces of gear plasma metering although beautiful wouldn't be practical giving all the power requirements plasma has. Oled became a real nice choice and probably aside from some expensive retro looking analog vu meter of some kind is the only choice. I need your ladies and gents help with arduino products and choices, I'm very happy to have found you , please help me , cheers and thank you
If you Google "Arduino VU Meter", you'll get quit a few hits. (I made a giant VU meter "effect", which isn't really a meter at all because it has an odd non-linear and non-dB scale and it self-calibrates to changing loudness for lots of full-range meter action no matter what the loudness or volume setting.)
Some things to be aware of...
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The Arduino's analog-to-digital converter is not quite fast enough for 20kHz audio. Practically speaking, there's not a whole lot of difference if you filter-out the highest audio frequencies from you metering, but if you want it to be perfectly accurate that might be a consideration.
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The Arduino can only accept positive voltages between 0 and +5V. If you want to read the negative-half of the waveform, you can bias the input at 2.5V with two equal value resistors and a capacitor ([u]example)[/u]. Or again, if you are not too concerned with perfect accuracy, you can ignore the negative half of the waveform (but you still to protect the Arduino from the negative voltage).
You can "capture" the peaks with a [u]Peak Detector Circuit[/u]. (This is what I used for my meter "effect".) A Peak Detector converts the peaks into a slow-discharging DC voltage, so your software doesn't have to be particularly fast. i.e., you can usually get by taking a reading 10 times per second or so. This particular schematic is a half-wave peak detector that ignores the negative half of the waveform, but you can build a full-wave peak detector. Depending on the design details, the peak detector can detect the fastest short-term high-frequency peaks.
The basic Arduino Uno has multiple analog inputs, so you could use separate inputs for the peak and average levels, or you can detect/calculate peak & average in software.
A couple more thoughts...
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Metering and recording levels aren't that critical with digital recording. You've got plenty of headroom, and as you may know, pros often record at -12 or -18dB (at 24 bits). Your software will have metering and you can analyze peak & average levels and adjust after recording. You audio interface may also have some limited metering (or at least a clipping indicator).
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A project like this will be time-consuming and you'll be playing around with electronics when you could be recording!
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If you want something that's cheap but fairly cool looking (and maybe useful), I ran across [u]this[/u] a few week ago. (I didn't buy one.)
DVDDoug thank you for the support I didn't think it was that complicated to integrate a digital display with analog hardware!!!! I've found very nice looking full color displays (TFT) some even with tactile capabilities , is Newhaven displays and was also trying to combine it with Microchips controllers , waiting for support to call and get the skinny on it but I truly appreciate your input , I will post a pic when and if I conquer the mountain !!!! thanks again and cheers
Hi,
What exactly are you metering? How many channels? At what point are your analog signals digitized?
I've been staring at VU meters since 1950 when I helped my Dad set up the remote broadcasts of Yale Interprets The News on Sunday nights in New Haven. VU meters has a very specific time domain response.
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VU: A VU meter is designed to have a relatively slow response. It is driven from a full-wave averaging circuit defined to reach 99% full-scale deflection in 300ms and overshoot not less than 1% and not more than 1.5%. Since a VU meter is optimised for perceived loudness it is not a good indicator of peak (transient) performance. Nominal sensitivity for 0VU is 1.228V RMS, and the impedance is 3.9K
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http://sound.westhost.com/project55.htm
and:
http://blog.shure.com/shure-tech-tip-vu-and-ppm-audio-meters-an-elementary-explanation/
Tell us more about your gear and what you would be recording and metering.
WayBack in AnalogHistory I designed a few recording studios, consoles etc..
It IS worth putting effort into metering. I think there is an elemental human thing going on there, maybe related to staring into the flickering fire. But then, I had that stuff imprinted on me at a very early age.