how do you set up a lm3914, i need one to show 4-5v and another to show 2.5-3v, do you just use 2 pots to adjust the low and high settings to where you need them?

 

Hi,
Look at this extract from the LM3914 datasheet, its shows what you are trying to do.

Use the formula in the sheet to calculate the 4v to 5v resistor values.

Do you follow.?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

so i adjust r1 to 1.2 then apply half the voltage i want the meter to display, then adjust r4 until the 5th led lights?

im new to electronics, so when i see "Vout = Vref (1 + R2/R1) + Iadj R2" that doesnt help so if you could give me a detailed example of how to calculate the resistor values that would help out a lot, like an example of how calculate the resistors needed for it to show 1-2v

 

hi,
Refer to the previously posted circuit.

For +1v to +2v input.,, 10 steps of 100mV

R1=200R variable
R2=1000R 1%
R3=1000R 1%
R4=500R variable

Set VD precisely to 1.00V [this is total span of 1V]
Set Vsig to +1.5V, adjust R4 until LED just turns ON

Do you follow .?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

can you show how you figured out the resistor values?

so you adjust R1 to set VD to the range you want the lm3914 to display? so for a 2 or 3v range, VD would be set to 2 or 3v? and once you set vd to the correct voltage you apply half of the max display voltage (for a display of 2-3v it would be 2.5v) to Vsig and adjust r4 untill the 5th led just lights?