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Old 05-07-2009, 01:35 AM
z-man z-man is offline
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Join Date: May 2009
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Default Voltage meter using LM3914

Hello! I am trying to replace an analog meter with a newer LED version in an amplifier, but am having problems with the input. What I want to do is display a max physical voltage of 0.28V (the max needle deflection of my analog meter) when I have my 30 LED's lit. I tried to find some sort of doubler/quadrupler circuit on the web to increase my voltage, but can't seem to figure out how to satisfy the input for the chip(s). Can this even be done? I was hoping not to modify any existing circuits in the amp. Any help will be appreciated.
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Old 05-07-2009, 01:59 AM
Audioguru Audioguru is offline
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Location: Ontario, Canada
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An LM3914 has a full scale sensitivity of 1.25V. For a sensitivity of 0.28V you must amplify the input voltage from 0.28V to 1.25V which is a gain of 4.46.
An opamp can be used as the amplifier.

The LM3914 is a linear voltmeter. An LM3915 is a logarithmic meter for audio levels and light brightness.
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Old 05-10-2009, 12:02 AM
z-man z-man is offline
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Thanks Audioguru, I guess I was just overlooking them for some reason. I decided on the LM6132 because of the low operating voltage, but was wondering if you might suggest something else?
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