Voltage attenuator for ADC input

Thread Starter

Mr Smiley

Joined May 1, 2010
6
Hi,

I'm trying to go through this with different values. I need a base voltage from 10-15 volts in and 0-2.5 volts out to feed an a/d, with a 15v single rail supply. But from the first section of the calculations i'm getting a gain of -0.5, do i just drop the - when calculating a value of 10K for R1 when using R2 as 20k as in your example. Also do i set Vd to 10v ?

Many thanks

Mr Smiley :)

Added Link to spawning thread: http://forum.allaboutcircuits.com/showthread.php?t=36896 (hgmjr)
 
Last edited by a moderator:

hgmjr

Joined Jan 28, 2005
9,027
mr smiley,

I have moved your request for help over to its own thread. It is best if you start your own threads when asking for assistance. You would not want anyone member to hijack your thread so be courteous and avoid hijacking other member's threads.


hgmjr
 
Last edited:

SgtWookie

Joined Jul 17, 2007
22,230
Oops - hgmjr, can you include a link to the original thread?

A simple voltage divider won't work to take a 15v-10v signal and change it to 2.5v-0v with a single 15v rail.
 

Thread Starter

Mr Smiley

Joined May 1, 2010
6
Hi everybody,

Hijacking wasn't intended, apologies to all. It was just Ron H's solution was what i needed. That thread was moved to another on my behalf, and now it's been moved again, could you tell me where it is :confused: I've looked around and can't seem to find it's new home.

ps, if it's any help, I've found the following web page which gives a op-amp calculator which seems very good for checking chosen resistor and voltages.

http://www.daycounter.com/Calculators/Op-Amp/Op-Amp-Voltage-Calculator.phtml

Mr Smiley :)
 

Ron H

Joined Apr 14, 2005
7,063
Hi everybody,

Hijacking wasn't intended, apologies to all. It was just Ron H's solution was what i needed. That thread was moved to another on my behalf, and now it's been moved again, could you tell me where it is :confused: I've looked around and can't seem to find it's new home.

ps, if it's any help, I've found the following web page which gives a op-amp calculator which seems very good for checking chosen resistor and voltages.

http://www.daycounter.com/Calculators/Op-Amp/Op-Amp-Voltage-Calculator.phtml

Mr Smiley :)
http://forum.allaboutcircuits.com/showthread.php?t=37845
 

Ron H

Joined Apr 14, 2005
7,063
Oops - hgmjr, can you include a link to the original thread?

A simple voltage divider won't work to take a 15v-10v signal and change it to 2.5v-0v with a single 15v rail.
See this thread for a way to do it with a single supply.

EDIT: Oops! I didn't notice that the output slope is inverted relative to the input.
ANOTHER EDIT: Our OP said 10V-15V. SgtWookie said 15V-10V. Which is it?
 

Thread Starter

Mr Smiley

Joined May 1, 2010
6
I'm getting confused now :(

This thread seems to be going round in circles, and moved to new threads; and at every stage confusion is creeping in.

It was original +10 to +15v shifted to 0 to +2.5v and got changed to 15-10v to 2.5-0v :confused: .Nobody's at fault, it just seemed to happen.

Ron has solved the problem for me, many thanks Ron, and many thanks to others.

Mr Smiley :)
 

Ron H

Joined Apr 14, 2005
7,063
I'm getting confused now :(

This thread seems to be going round in circles, and moved to new threads; and at every stage confusion is creeping in.

It was original +10 to +15v shifted to 0 to +2.5v and got changed to 15-10v to 2.5-0v :confused: .Nobody's at fault, it just seemed to happen.

Ron has solved the problem for me, many thanks Ron, and many thanks to others.

Mr Smiley :)
Can you post your solution?
 
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