Here is High-performance LM3914/LM3915 VU meter circuit projects that can display with 20 LEDs on stereo or mono with 10 LEDs for all audio system. and can easily build and cheap you must happy when use it. This electronic VU meter set is a circuit that High performance and widely popular than 40 years.
I made a lot of amplifiers. Because I like to listen a music. Also, I like the VU Meter circuits too. They show power level of the audio. It is so beautiful.
Many friends may prefer them same me. When you go to an electronics store to buy a VU meter kit. In pattern, assemble the various parts on their own and ready using.
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Why build LM3914 VU Meter circuit
Most freiends choose LM3914 VU meter circuit. Because it is convenient, easy to modify in many form. Today I assemble a the circuits that use this IC. Sometimes you are looking for ideas on this.
For example: Flashing lights by the band, to decorate the Christmas tree, exotic, and unique.
This project is very easy. Because of use alone IC only and a few external components. The display system can drive directly LED up to 10 LEDs and display as light running is DOT or BAR as you want.
follows by Figure 1
The working principle
The main in working of this circuit is LM3914N or IC LM3915N as suitable for your working. Which the external circuit is the same.
The difference of the two ICs is that:
- LM3914N will display an amplitude of a signal in Linear form.
- LM3915N will display the signal in Logarithm form.
Normally if using the amplitude of sound signal. We should use the LM3915N.
The input signal from power amplifier will be entered through to Voltage Doubler circuit consists of C1, C2, D1, D2 to convert sound signal voltage to DC voltage and have amplitude are 2 times of the input signal. Then, insert single to input pin 5 of IC.
And next IC will compare the signal amplitude, to drive LEDs display follows amplitude of input signal as above.
The Mode selection in working of circuit. to display in Dot or Bar form. The ability do with connecting a switch to pin 9 of IC. Which if indiscreetly release the switch will display is bar form. But connected the switch to pin 9 together with a positive voltage, the circuit will display in the dot form immediately.
Build this projects
First of all, makes the PCB layout in stereo or mono as you need. Secondly, soldiers all components into the PCB, as you see in Figure 2 (stereo form) and Figure 3 (Mono form). Caution: Polarity of LED must be placed correctly. If you reverse the polarity, the LED does not light.
The parts list
D1, D2—1N4148__ 75V 150mA Diodes
R1—10K Resistors 1/4W
R2—2.7K Resistors 1/4W
R3—3.9K Resistors 1/4W
C1, C2—1uF 50V electrolyte capacitors
C3—47uF 16V electrolyte capacitors
1. If you need to print the PCB layout please check 200 dpi per inch on image scale.
2. If you not like this circuit please look at:
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