Simple 3-Level Level Indicator/Warning Lights Idea

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beatpoet

Well-known member
Joined
Sep 19, 2006
Messages
334
Location
Michigan
It's been a while since I've picked at my pile of transistors or posted here, but here is an idea for a mix indicator light for easy level monitoring.

I'm thinking I'd like to build a nice level indicator in the form of 3 lights. If the level is below a certain threshold, say .33vDC for example, then the green light will be lit. If the level is between about .33V.DC and .66vDC then the blue light will be lit, and when the level is above .66vDC then the red light will be lit.

Does anyone have any ideas about how I could lay this out or how to really get started? I'm really trying to knock the rust off of the brain cells on this one, so simple is best!

 

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> knock the rust off of the brain cells

Too much work. If you aren't making a million, just mis-wire LM3914.

Actually 0.3V 0.6V is a mighty narrow range. IMHO the LM3915 will be more useful.
 

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It depends on how clever you want to be.  I have made many simple level present/overload indicators for secondary console audio paths with bicolor LEDs, (typically with one op-amp or a couple transistors). I even made a threshold calibration indicator, from a bi-color LED that was green below threshold, red above threshold, and both on, at threshold, for a defunct vinyl NR  kit (CX).

The simplest approach for driving three LEDs if you are flexible about the thresholds is something like PRRs 3914/5 approach. If you want more control over precise thresholds a slightly more complex custom meter can be assembled from a inexpensive quad comparator (LM339) and a handful of passive components to establish thresholds, and LED currents.

JR
 
 
Your problem statement implies one-at-a-time lights.

Simple LM339 ladder is bar-graph.

This is a simple dot-mode:
 

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You've probably thought of this, but you may find a logarithmic scale more useful for audio monitoring.

So 1V, 0.1V, 0.01V.
Or  1V, 0.37V, 0.14V.

Anyway, something like that!
 
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