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| Ev Archive for July 1998 |
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| 1169 messages, last added Wed Aug 08 18:42:41 2001 |
[Date Index][Thread Index]
Re: Bar graph voltage monitors
>Integrated Bar Graph Display TSM3914 with 10 LED segments, linearly
>scaled for 5v deviation with accuracy of 1% @ 25C.
Correct part number is TMS3914. See National Semiconductor's catalog (LM3914)
for lots more circuits and application data (they invented the part).
The internal reference is not very good. It varies 5% from part-to-part,
drifts 1% with temperature, and another 1-2% with various circuit loading.
Since battery voltage changes less than 10% from full to dead, you'll need to
include trimpots to calibrate each one individually.
You can improve its accuracy, but I wouldn't bother. Simple voltage
measurements are intrinsically not very accurate. Just use them as a simple
relative "fuel" indicators. The differences between batteries is much more
important. Use a real meter for actual voltages.
Last I knew, Radio Shack sold a little module with this chip and the 10 LEDs
already pre-wired.
Lee Hart If you would not be forgotten
4209 France Ave. N. Soon as you are dead and rotten
Robbinsdale, MN 55422 USA Either write things worth the reading
phone (612) 533-3226 Or do things worthy of the writing
e-mail XURQ03A@prodigy.com (Ben Franklin, Poor Richard's Almanac)
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