I have been trying to use the LM3914 to display output up to 20 or 25 volts (a readout for a generator my daughter is building). It seem simple initially, follow the formulas in the data sheet. Not!!! I have a couple of questions.
1. Does the supply voltage for the IC need to be 1.5vdc greater than my 20 or 25 volts?
2. After using the formula to determine LED current 12.5/R1, it seems I should use 20/R where R= the sum of R1 & R2 in parallel with the 10K internal divider. Is this correct?
I had planned to use R1 = 680, R2 = 10.2K, which should give a 0 - 20 volt range, but now I'm not so sure.
Any suggestions would be greatly appreciated.
Thanks,
1. Does the supply voltage for the IC need to be 1.5vdc greater than my 20 or 25 volts?
2. After using the formula to determine LED current 12.5/R1, it seems I should use 20/R where R= the sum of R1 & R2 in parallel with the 10K internal divider. Is this correct?
I had planned to use R1 = 680, R2 = 10.2K, which should give a 0 - 20 volt range, but now I'm not so sure.
Any suggestions would be greatly appreciated.
Thanks,