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LM3915 math

Diver300

Well-Known Member
Most Helpful Member
Back to the math I was bitching & whining about at the start of this thread: Am I correct in assuming the voltage values to be consider for calculating resistors on pins 6, 7 & 8 should be the "Typical Output Voltages" of 1.28v as listed on page 4 of the data sheets? Am I getting that right?
Yes, the typical values are what you would use.

If the voltage limits are critical, you should also look at the minimum and maximum values, but that's not usually necessary.
 

audioguru

Well-Known Member
Most Helpful Member
The difference between 1.25V and 1.28V is only 2.4 percent which does not matter. Your measurements are all much higher and are all high (not low) so maybe your meter is also Chinese?

Most Western Name Brand companies have factories in China but they have proper Quality Control. Many Chinese companies (especially the ones who make fake parts) have no quality control.
 

Super-Dave

New Member
The difference between 1.25V and 1.28V is only 2.4 percent which does not matter. Your measurements are all much higher and are all high (not low) so maybe your meter is also Chinese?
Yes of course it's Chinese. However, it's withing a couple hundredths of the plug-in cigarette lighter meter in my car, so I trust it. It's a multi-meter. I test all my components with it. The Amazon 1% resistors all do read within 1% of their rated values too, one of the few components that have been consistent right out of the box. It also has the option to test capacitors too, but I haven't figured that one out yet. Lost the instruction booklet years ago before I got into this "hobby".
 

ChrisP58

Well-Known Member
Most Helpful Member
Yes of course it's Chinese. However, it's withing a couple hundredths of the plug-in cigarette lighter meter in my car, so I trust it. It's a multi-meter.
Having two things of questionable origin that agree with each other doesn't mean either is correct.
 

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