hi alex,
I was going to post a link to my Forum Blog for the LM3914 calculator,,, but for some unknown reason its says I have deleted it, which is incorrect.!!!
My questions:
1 - I can't define R2 (don't know Vout or VR2)
2 - is right the R1 value?
3 - is right the R3 value?
4 - how determinate R on pin5 (need it or not?)
5 - how can I determinate Vled=3V?
R2 is calculated from Vmax, you state its 5V, but you only have a LM3914 supply voltage of 5V, you MUST have at least 1.5V to 2V higher for the supply above your Vmax in.
R1 is chosen to give the required LED current.
R3 sets the Vmin for LED#1 to light, which is also dependant upon I3 which a function of Vmax voltage.
The R on pin#5 is not required.
The Vled is determined by the colour/type of the LED's that you are using, not the LM3914
Different colours have different Vfwd.
For a Vmax of 5V use a 9V battery and set the LED current to about 15mA.
Do you follow OK.?