- #1
Can Some Help Explain This Circuit to me? its a LED Audio VU meter circuit
Click For Summary
Discussion Overview
The discussion revolves around understanding the workings of an LED audio VU meter circuit, specifically using the LM3915 chip. Participants seek clarification on various components and their functions within the circuit, including the reference DC voltage and the variable resistor.
Discussion Character
- Exploratory
- Technical explanation
- Conceptual clarification
- Homework-related
Main Points Raised
- One participant requests help with understanding the circuit, indicating it is a personal project rather than homework.
- Another participant describes the circuit as taking an audio input, using a volume control, and lighting up LEDs based on the input strength.
- A participant identifies the chip as an LM3915 and notes that the circuit resembles the example provided in the datasheet.
- Further clarification is sought regarding the purpose of the reference DC voltage connected to the top LED and the function of the variable resistor.
- One participant explains that the DC voltage is the power supply for the LEDs and that the variable resistor sets the gain/level of the input to prevent overdriving the chip.
Areas of Agreement / Disagreement
Participants generally agree on the basic function of the circuit and the role of the LM3915 chip, but there are still questions and uncertainties regarding specific components and their interactions.
Contextual Notes
Some assumptions about the circuit's operation and the specific roles of components remain unresolved, particularly regarding the overall output generation through the LM3915.
Who May Find This Useful
Individuals interested in electronics, circuit design, or those working on similar audio visualization projects may find this discussion beneficial.
- #2
schip666!
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It would of course help to know the chip number or whatever...
But I'm not sure what needs explaining? It looks like it takes an audio input, through a "volume-control", compares it to a reference set with two resistors, and then (maybe?) lights up an array of LEDs based on the strength of the input.
Do you have some more specific questions?
But I'm not sure what needs explaining? It looks like it takes an audio input, through a "volume-control", compares it to a reference set with two resistors, and then (maybe?) lights up an array of LEDs based on the strength of the input.
Do you have some more specific questions?
- #3
uart
Science Advisor
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The chip is an LM3915 and yep it's just a bunch of comparators set to switch in the LED's at different levels of the input signal. The circuit is pretty much the datasheet example for this IC. Not really much to explain.
- #4
AlephZero
Science Advisor
Homework Helper
- 6,999
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That's what "LM3915" on the circuit diagram means.schip666! said:
The circuit is straight from the datasheet http://pdf1.alldatasheet.com/datasheet-pdf/view/8899/NSC/LM3915.html
What specifically don't you understand?
- #5
SammHunka
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Basically i just need help understanding what the reference dc voltage connected to the top LED is for, what the variable resistor is for, and basically how the overall circuit works (meaning how the output is created through the lm3915). sorry about the mix up!
- #6
schip666!
- 594
- 0
AlephZero said:That's what "LM3915" on the circuit diagram means.
What specifically don't you understand?
I don't understand how I managed to miss that is what I don't understand...
- #7
davenn
Science Advisor
Gold Member
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SammHunka said:
the DC voltage connected to one side of ALL the leds is the + power supply for those LEDs
The variable resistor is to set the gain/level of the input to the chip so that you don't overdrive it. overdriving it could ...
a) damage the input to the chip
b) mean that ALL the LED's would be permanently lit up so you wouldn't have any meaningful variation in the LED display
Dave
- #8
SammHunka
- 3
- 0
Thank you dave and the rest of you guys! presenting it to my peers tomoro so i will check back with how it went! much thanks!