Single supply absolute value converter - Electronic Circuits Projects Diagrams Free

pikstart · 26th May 2007, 11:31 AM

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** · 26th May 2007, 12:26 PM

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 · 26th May 2007, 12:43 PM

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** · 26th May 2007, 01:11 PM

Quote:

Originally Posted by 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!

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 · 26th May 2007, 01:36 PM

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

http://www.national.com/pf/LM/LM3914.html

Also the LM3915 log type for audio levels

pikstart · 26th May 2007, 01:42 PM

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

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26th May 2007, 11:31 AM	(permalink)
pikstart	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 __________________ www.signalcom.gr Last edited by pikstart; 26th May 2007 at 11:34 AM.

26th May 2007, 12:26 PM	(permalink)
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. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

26th May 2007, 12:43 PM	(permalink)
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 __________________ www.signalcom.gr

26th May 2007, 01:36 PM	(permalink)
ericgibbs	hi pikstart, There are devices for displaying 'bar graphs'. http://www.national.com/pf/LM/LM3914.html Also the LM3915 log type for audio levels __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

26th May 2007, 01:42 PM	(permalink)
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 __________________ www.signalcom.gr