11/28/2023 0 Comments Vu meter leds![]() ![]() The 10 ohm resistor isolates the earth connection to help prevent hum if the same transformer is used to power a preamp (for example).įigure 2 - Power Supply Circuit (Single 15V AC Winding) One 15V output goes to the terminal AC1, the other to AC2. The peak current is about 120mA DC, so a 5VA transformer will be sufficient to power two meter circuits. You can generally use the smallest one available, as average power is quite low. Power comes from a 15V transformer (connected to AC1-AC2). ![]() ![]() Dot mode uses far less current, but the display is not as visible. If the jumper is omitted, then only the LED corresponding to the current signal level will light. With the jumper installed, the unit operates in bar mode, meaning that LEDs will light in a continuous bar. This is designed for direct connection to high-level preamps or low power speaker output of an amplifier. ![]() As shown, full scale sensitivity (with VR1 at maximum) is 4 Volts peak (approximately 2.8 volts RMS). This gives a 9dB overload margin when the unit is calibrated as described below. L1 to L7 will normally be green (normal operating range) and L8 to L10 should be red (indicating overload). This increases the size and cost of the project - especially important if it is to be used in larger numbers as may be the case with a mixer or analyser. This allows a higher LED current with lower dissipation than would be the case if the DC were fully smoothed, and full smoothing would also require a much larger capacitor. DC to the LEDs is almost unfiltered - C1 is included to make sure the IC does not oscillate, and is not a filter cap. The circuit is shown in Figure 1 and as you can see it uses a single IC and a few discrete components. The circuit is completely conventional, and is based on the application notes from National Semiconductor. They are ideal as power meters on amplifiers, can be used with mixers (including the high quality mixer described in the project pages), preamps and any other application where it is important to know the signal level.įigure 1 - Photos of Two Versions of the LED VU Meter There are many other uses for a simple LED VU meter. This project is also an essential part of the expandable analyser to be published soon (or perhaps "eventually"), and one meter circuit is used for each frequency band. Each LED operates with a 3dB difference from the previous one, and a jumper is provided to allow dot or bar mode. This version is based on a National Semiconductor IC, and uses the logarithmic version. The LED meter is simpler and smaller than its analogue counterpart, and is very common in audio equipment. It is quite true that there are many variations of this circuit already on the Net, but for the sake of completeness - and because there are PCBs for this version - here is yet another. Source: Note: PCBs are available for this project. It is much easier to use with a microphone.įILE DOWNLOAD LINK LIST ( in TXT format or file): 27779a.rar pass: In addition, I tested with the circuit in the article “Strip Led Microphone Vu Meter Circuit” that I shared before. RGB strip led is not bad, but separate leds provided a better view. As you can see in the video, I experimented with RGB strip leds and separate strip leds. More powerful mosfets and coolers are required for led strips in larger quantities. Color Music RGB Strip and Separate Led Strip Test video ĭepending on the type of led strip, 5…10 meters of led can be connected per channel. The mosfets used in the ATtiny13 outputs can be 50N06, IRFZ44, IRF3205. The 100k resistance on the ATtiny13 audio input pin 3 was too much, I used 39k in the tests. I set up the circuit on a breadboard and tried it, I used the MP3 player output as the sound source. The schematic of the Color Music circuit and the amplified ATtiny13 outputs with mosfets This project is also a good example showing that real time DFT (Discrete Fourier Transform) is only possible in small MCU like ATtiny13 with 64B RAM and 1024B FLASH. The project uses Audio Signal Acquisition ( ADC, Signal Sampling) and DSP (Digital Signal Processing) calculations, which in real time separate the three frequency bands and enable LEDs to light in sync with the music. ![]()
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