Circuit help: 5-0v scaled the 0-1v

[the poi]

I have a sensor (a wideband o2 sensor, for those intersted) that outputs a voltage from 5-0v. I however am trying to figure out a way to scale that voltage linearly to a 0-1v output. Im afraid I haven't had much of a background in electronics however, so I'm more or less lost from the onset. Anyone have any suggestions on how I can go about his? Thanks for any info...

[bridgen]

You can do it with a single op-amp, which will need both positive and negative supply rails.<p>Connect it in the inverting configuration.
Make the input resistor 5 times the value of the feedback resistor. e.g. input R 10k, feedback R 2 x 1k in series. <p>Connect the non-inverting input to a a source of 0.833V, which could be obtained from a resistive voltage divider across a couple of diodes. <p>That's it. <p>When the input voltage is 5, the output voltage will be 0.
When the input voltage is 0, the output voltage will be -1.

[bridgen]

Whoops.<p>When the input is at 0V, the output will be at 1V, not -1V.

[the poi]

Thanks for the fast reply! Any suggestions on a part number of op-amp to use (I'm afraid I'm lost outside of resistors and voltage ) Also, could you elaborate on the diodes in the voltage divider? Since this design calls for a regulated supply voltage, how could I go about stabilizng the 12v car input (that probably can change anywhere from 10-14v) to use as the supply voltage? Thanks again

[bridgen]

Because the circuit requires a negative voltage supply in addition to a positive one you won't (easily) be able to run it off a vehicle's nominal 12V. <p>There are special chips available which will give you a negative rail from a positive supply. I can't remember type numbers (if I ever knew them). They are available from RS Components in the UK, you can find them at rswww.com
There will undoubtedly also be suppliers in the 'States.<p>If you are determined to use it in a vehicle then I would suggest using a 3-terminal 9V regulator and run a -5V rail generator from the 9V. <p>To get the reference voltage you could have a zener diode, or a couple of signal diodes, with a current limiting series resistor, across the positive supply, and a resistive divider across the diodes. It would be useful to incorporate a potentiometer so that you can twiddle the exact voltage (actually you would twiddle for either 0V out with 5 in, or 1V out with 0 in).

[the poi]

Damn, I'm afraid this is all over my head... any possibility someone could draw up a rough circuit diagram, or maybe give some more specifics what I would need to wire up? In any event, thanks for your help so far David

[russlk]

I posted a schematic on my website. You may have to copy and past the URL because Geocities does not allow links.
http://www.geocities.com/russlk/vcnv.jpg<p>I forgot the divider resistors for .833 volts. They are connected from 5 V to gnd and are: 49.9K and 10.0K.<p>[ June 10, 2004: Message edited by: Russ Kincaid ]</p>

[the poi]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Russ Kincaid:
I posted a schematic on my website. You may have to copy and past the URL because Geocities does not allow links.
http://www.geocities.com/russlk/vcnv.jpg<p>I forgot the divider resistors for .833 volts. They are connected from 5 V to gnd and are: 49.9K and 10.0K.<p>[ June 10, 2004: Message edited by: Russ Kincaid ]<hr></blockquote><p>wow, thanks a whole hell of a lot Russ! I really appreciate it, thanks to both of ya!