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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #1  
Old 05-07-2009, 01:35 AM
z-man z-man is offline
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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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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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