1v-5v output linearly by using 5v supply, voltage divider and variable resister

[Bhadresh]

How can i get 1v-5v output linearly by using 5v supply, voltage divider  and variable resister  ?

[Tom__Sedlack]

Ohm's Law.  

Calculate a resistive voltage divider where 4 volts is dropped across 1 resistor (R1) and 1 volt is dropped to ground across the second resistor (R2).  Then replace  R1 with a linear potieniometer.  To make life a little easier, use a standard potieniomete resistance value for R1 since pots come in limited values.  Then just calculate for R2 where you have a much better chance of getting the needed value. 

[Bhadresh]

Thanks for replying...

But when we calculate it for 1v and 5v, it is right but when we  calculate it for half or in between then it is not linear .

[Tom__Sedlack · Accepted solution]

Do you have it wired like the attached file?  Using my schematic, you can calculate the current through the pot based on the desired voltage drop across the pot

4V / 10Kohm = 0.0004 A

From Kirchhoff's current law, we know the same current will flow through the circuit so now we can calculate the lower leg of the divider based on the current and the desired voltage drop across the resistor

1V /  0.0004 A = 2.5K Ohm

My schematic keeps the current through the circuit constant so the voltage divider should never change.  Assuming a linear pot, you will get a linear voltage swing as measured at the wiper.  If you wired the pot a different way, then more then likely, you are changing the total resistance from 5V to ground which would effect the current which would effect the voltages.

[Bhadresh]

thank you