Single supply absolute value converter

[pikstart]

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

 

[Nigel Goodwin]

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.

 

[pikstart]

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

 

[Nigel Goodwin]

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!

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.

 

[ericgibbs]

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

**broken link removed**

Also the LM3915 log type for audio levels

 

[pikstart]

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