lm3914 calculation

hello.

i want my LM3914 (dot/bar driver) to measure a voltage source from 380v to 730v.

i have a DC source varying between 380-730v, i want the first led to be on at 380v, and the last led on at 730.

i need the schematics resistor values,
how can i calculate them ?

i tried different values with trimmers but couldn't get it precise scale.

thanks !

... just an idea

I have been looking at the following schematic ... with reference to your request:
**broken link removed**

I am not completely confident about it, but there may be a way to modify this circuit to conform to your specifications.

You would remove the bridge rectifier component, as well as D11, and connect the 730 to 380 DC voltage across the resistor divider chain ...R2-R3-R5-R6.

If I understand correctly, the purpose of the diode bridge is to supply the zener diode, in order to get +9 volts to supply the chip. You might construct a separate voltage divider, with reference to ground, to supply a zener diode, in order to accomplish this.

.... probably need to draw up a new schematic, just to make sure that everything is clear.

730vdc is very dangerous. If you do not know what your doing you should not mess with it.

Mikebits said:

730vdc is very dangerous. If you do not know what your doing you should not mess with it.

Click to expand...

Hopefully, the original poster will be aware of that, and have the necessary experience to deal with this circuit .... in a safe manner.