New LED display design, help me perfect it!

[The Tone God]

What do you mean by noise problems?

You calibration cycle could be thrown off by noise in the system environment.

Andrew

[RaceDriver205]

Nah, I don't think that'll be an issue.
Is it OK to do what I did with the opamp? I set the non-inv input to 0V, so only the top half of the wave gets amplified and passed through. Then it is smoothed to near DC, giving the ADC something which is proportional to the amplitude of the wave. (Ill get it to ADC 8 times and then average for better accuracy).
Cheers Andy

[The Tone God]

Nah, I don't think that'll be an issue.

Famous last words.

Is it OK to do what I did with the opamp? I set the non-inv input to 0V, so only the top half of the wave gets amplified and passed through. Then it is smoothed to near DC, giving the ADC something which is proportional to the amplitude of the wave. (Ill get it to ADC 8 times and then average for better accuracy).

No I don't think that is good way to use the opamp. Put in the resistor network on the non-inverting input and throw a diode on the end, if you are worried about losses use a Schottky, to rectify the output then filter. There is a reason why envelope filters after all these years still use this arrangement.

One thing you will have to figure out is how fast you want the response of the network. Low values will increase speed but if you go too small ripples will come through potentially screwing up your readings. Too large values will give a slow response.

Andrew

[RaceDriver205]

Low values will increase speed but if you go too small ripples will come through potentially screwing up your readings.

Well im going to go and buy an oscilloscope today. I think its high time! - That and I found a good deal 

I seriously can't see how noise will be an issue. The guitar signal will be way louder than the noise, and the gain will set so that the guitar signal is at max amplified to 4V. As far as I can see, the noise would only be an issue if the calibration stuffed up and set the gain too high. In which case the machine wouldn't work at all anyway. This could only happen if you failed to play the guitar at full volume when it was calibrating.

[The Tone God]

Well im going to go and buy an oscilloscope today. I think its high time! - That and I found a good deal 

Great. You are going to have a lot of fun with that toy.

I seriously can't see how noise will be an issue.

Oh I'm just giving you caution. Keep an eye on things which you can do with you new scope.

Andrew

[RaceDriver205]

Ah ha OK here it is.
The circuit is nonsense. Using my scope reveals that you obviously need a far superior circuit to get a good steady average of the signal. FAR superior.
To this end, and as I am not really interested in this device anymore, this project will remain a preliminary sketch. A good idea, but not worth it.

[QSQCaito]

I read this post a long ago, cant remember exactly what were you doing. I found thi info, hope it helps..

http://www.talkingelectronics.com/te_interactive_index.html