Single supply absolute value converter

Dear members,

I need help on a project to convert audio signal to DC so a MCU can sample it and display it like bar on an LCD.

The problem I have is that the absolute value converter (like the example from Art of Electronics) needs to operate on a double supply, e.g. +/- 15 Volt.

I need it to work on a single supply, prefferably on +5. LMC662 is OK for 5V, but how will the circuit be biased?

Any help appreciated,
John

You simply bias the A2D at half of it's Vreg (so 2.5V for 5V Vref), and capacitor couple the audio signal to it.

Thanks Nigel.

I forgot to mention that the DC output is going to be converted to binary with the help of a PIC. So a 0-5 somenthing would be preffered than a 2.5 to 5.

That is the point of my question regarding the bias. I need the circuit to work like having symmetrical supply!

Regards,
John

pikstart said:

Thanks Nigel.

I forgot to mention that the DC output is going to be converted to binary with the help of a PIC. So a 0-5 somenthing would be preffered than a 2.5 to 5.

That is the point of my question regarding the bias. I need the circuit to work like having symmetrical supply!

Click to expand...

That's EXACTLY what I gave you, the output will be from 0-1023, but it represents -2.5V to +2.5V, with 0V input represented by 511/512 (assuming using a 10 bit A2D) - which is what you need.

hi pikstart,
There are devices for displaying 'bar graphs'.

**broken link removed**

Also the LM3915 log type for audio levels

Thank both.

Nigel, I was thinking just 0-5 for the analog signal. Yes, you are absolutely right about that. Sorry for the trouble.

Ericgibbs, I know that chips, but for the project under discussion, I need to display the values to an LCD (4x20) along with other values (+5, +24, +48 and the audio as a bar-graph).

Regards,
John