Digital displays on σ22 and β22 - how hard?
May 20, 2009 at 3:06 PM Thread Starter Post #1 of 11


Apr 30, 2009
Hi there,

How hard is it to add a small digital volt meter on the sigma22 and a db meter or an analog vu meter on the beta22?

I do like clean designs, but I also love my hardware to have readings on it.

Has anyone done similar mods before?

May 20, 2009 at 3:33 PM Post #2 of 11
I know for a fact that the arduino chip (that I'm using quite heavily these day) has some nice 10bit a/d input pins (6 of them). you can prescale them (voltage divider) and then you'll get 10 bits of res.

there are also some really high bit res chips (24bit a/d) in the $10 range that will output a serial stream, readable easily by the cpu. according to one source, the 24bit chips are a real honest 20bits of analog data (not sampled fast enough for audio but definitely fast enough for a meter!).

that would handle the voltage rails.

for the vu meters, you would want to convert and smooth the varying analog out to some kind of averaged dc - and feed THAT into the a/d pins and sample them as often as you like. getting the 'weight' might be the only tricky part (to keep the meters 'bouncing' in the right way).

I've been thinking of a side project related to this - that would monitor 4 (say) voltage lines and report to the user on some lcd screen. this might be useful on watching bias voltages, etc.

along the same lines, they make temperature reading chips (with i2c output) that you could also read via one of the serial lines and report on.

my background is networking and data-comm and the notion of 'manageable devices' is very key with me
in my world, everything is manageable from airflows on chassis fans, to voltage rails, to power consumed, to error rates, counters, status values and so on. you can literally get hundreds of bits of data when you 'walk' a networking box and ask it for all its manageable entity data.

I almost see the same kind of thing happening to audio, at some point; as controllers get more acceptable to end users and the industry and as people want more and more 'features' on their devices, including remote management.

hmmmm - maybe someday cisco will make hi-fi gear (lol!)
Jun 1, 2009 at 6:03 AM Post #3 of 11
There was a large VU meter that was posted as a project on sparkfun a while back that you might be able to refer to. They used a display that is probably alot larger than what you would want but it might give you some ideas. If you are at all interested in diy electronics spark fun is a really cool site to check out. They have some great tutorials and blog posts and some of the products they sell are pretty cool too.

SparkFun Electronics
Jun 1, 2009 at 3:19 PM Post #4 of 11
I didn't think of Arduino at all. SparkFun's article also looks very interesting.

I'm just starting to gather the parts needed for the b22 amp so I will take a look at both suggestions.

Thanks both of you!
Jun 3, 2009 at 8:42 AM Post #6 of 11
Agreed, the Arduino is probably the best way to go. In fact I have already done something like this myself.

The voltage from the Sigma22 goes into a voltage divider -> opamp so both rails can be measured. (the arduino can only measure between 0 and +5V)

Jun 16, 2009 at 10:40 AM Post #10 of 11

Originally Posted by mattcalf /img/forum/go_quote.gif
Also check this out.

loving the idea of re-using a hdd chassis!

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