Min/Max settings for 0-10v control voltage

Thread Starter

Salomonander

Joined Mar 31, 2022
17
Hey there,
this is my first post, so hello everybody!

im looking for a circuit allowing me to apply min/max settings for a varying 0-10v analog control voltage. i need to limit the 10v range to a 2v range between 1v-3v.
i would like to be able to vary these limits with trim pots if possible.
i found a circuit for a fixed supply voltage, but nothing for a varying one. it would be great, if anyone could point me to a fitting circuit.

thanks a lot!
jakob
 

Papabravo

Joined Feb 24, 2006
18,783
You can run the 0-10V signal through a gain stage with a gain of 0.2 which will convert it to a 0-2V signal and the add it to a constant value of 1 volt to get a signal that varies from 1-3 volts. Completely standard opamp stuff.
 

AlbertHall

Joined Jun 4, 2014
12,071
To be clear, do you want to scale the input or limit it?
Scale: 1V in gives 1.2V out, 9V in gives 2.8V out.
Limit: Anything less than 1V in gives 1V out, anything more than 3 V in gives 3V out, 2.5V in gives 2.5V out.
 

Thread Starter

Salomonander

Joined Mar 31, 2022
17
Hey thanks for the replies
i want to scale them just as described by AlbertHall. It would be great if i could somehow set the limits with trim pots. my supply voltage is either 24v or +-15v. My max limit will never be above 5v. My min limit never below 1v. The input range will always vary between 0-10v. Thanks!
 

Papabravo

Joined Feb 24, 2006
18,783
Hey thanks for the replies
i want to scale them just as described by AlbertHall. It would be great if i could somehow set the limits with trim pots. my supply voltage is either 24v or +-15v. My max limit will never be above 5v. My min limit never below 1v. The input range will always vary between 0-10v. Thanks!
This circuit will do a linear transformation on a 0-10V signal. It can be reconfigured to perform any similar transformation and can also be adjusted with potentiometers. The first amplifier inverts and scales the incoming control signal. The second amplifier inverts and sets the offset via resistors R7 & R8. Any linear function of the form y = mx + b can be realized in this fashion. It is necessary to use an inverting configuration because the non-inverting configuration cannot realize a gain of less than 1, when configured as a unity gain follower.

1648776286398.png
 
Last edited:

crutschow

Joined Mar 14, 2008
30,098
Papabravo beat me by a minute. ;)

Below is the LTspice simulation of a two op amp circuit that I think does what you want.
The output is shown for both limits of the gain and offset adjustment pots with a 0-10V input (horizontal axis).
I used the ±15V supplies you have available.

1648776438888.png
 

Thread Starter

Salomonander

Joined Mar 31, 2022
17
Papabravo - thanks!
what value would i use for r7 and r8 if id want this to be 1v-5v instead? I just want to see what size of trimmers i need in order to fit my range.
 

Thread Starter

Salomonander

Joined Mar 31, 2022
17
Crutshow - say i want to lower the starting point back to 0v - is that possible with the given resistors? Or would i need to change anything?
 

Papabravo

Joined Feb 24, 2006
18,783
Papabravo - thanks!
what value would i use for r7 and r8 if id want this to be 1v-5v instead? I just want to see what size of trimmers i need in order to fit my range.
The span is set with resistors R1 & R2
To map 0-10V into 1-5V, you compute the gain as (5-1) / (10-0) = 0.4. You could change R1 from 4K to 8K and 8K/20K = 0.4

To get the reference voltage Vr at the junction of R7 & R8 you proceed as follows, by writing KCL :
(Vi - Vr)/10K = (Vr - Vo)/10K​
Vo = 2*Vr - Vi​

In the first amplifier you know several points:

0V -> 7V,​
5V -> 5V, &​
10V -> 3V​
because there is an inversion about the midpoint of the range. In the second amplifier you want to map the outputs from the first amplifier as follows:

7V -> 5V,​
5V -> 3V,​
3V -> 1V​
Pick any of those mappings and substitute

3V = 2*Vr - 5V​
8V = 2*Vr​
Vr = 4V​
You can keep R8 equal to 15K and change R7 to 22.6K, Vr will be equal to 4 Volts and the DC transfer function will be y = 0.4*x + 1
Note: The values of R7 & R8 are not unique. Any pair of values that gives 4V at the non-inverting input will do.



 
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