Introduction: Led Vu Meter LM3915
Good afternoon, dear viewers and readers. Today I will tell you about the LED volume unit meter, built on the basis of the integrated circuit LM3915.
Step 1: Links to Radio Components.
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You can find all the necessary information for repeating this device by clicking on the link to Patreon:
LED VU Meter Kit on Tindie:
Links to radio components:
Radio parts store:
DC power connector:
Header & Socket connectors 2.54 mm:
Mounting plastic racks:
Tantalum Capacitor 22 uF uF 16 V:
Capacitor 105J uF 100V:
Power Supply 220V 1A:
Step 2: LM3915 Block Diagram.
The LM3915 block diagram consists of ten comparators, on the inverse inputs of which an input signal is applied through a buffer operational amplifier, and direct inputs are connected to the taps of the resistive voltage divider.
The outputs of the comparators are sink current generators, which allows you to connect LEDs without using limiting resistors. Indication can be made either by one LED (point mode), or by a line of luminous LEDs, the height of which is proportional to the level of the input signal (line mode).
Step 3: Microphone Amplifier Circuit.
The input signal will come from a microphone amplifier, assembled on a low-noise operational amplifier NE5532, at the input of the LM3915 microcircuit chip.
The circuit contains two stages with controlled gain. The gain of the first stage is continuously adjustable by a potentiometer in the range of 1 ... 10 times. The gain of the second stage can be changed in steps using a jumper. If the jumper leads are not shorted together, the gain will be greatest, which is determined by the ratio of R8 and R5 resistors. When a jumper is connected to R6 or R7 in parallel with R8, the gain will be less.
Step 4: Circuit Design and PCB Layout.
On the EasyEDA website, one common circuit was designed out of two circuit diagrams and converted into a double-sided printed circuit board.
A separate circuit diagram and a printed circuit board were designed for the LEDs.
There are two LEDs connected in series at each indication level.
Step 5: 3D Visualization.
In KOMPAS 3D I created a model in the form of a tower of identical rectangular parts. I will use 5 mm thick organic glass as rectangular parts to improve the light scattering of LED indicators.
Step 6: Installation of Radio Components on the Control PCB.
Let’s proceed to the installation of the radio components on the control circuit board.
Step 7: Installation of LEDs on the PCB.
Next, we proceed to the installation of the printed circuit board and the LED linear.
Step 8: Connection the Control Circuit Board and the LED Circuit Board
With the help soldering, connect the control circuit board and the LED circuit board together.
Soldering of joints is done both on the outside and on the inside.
Step 9: Assembly of the Tower From Rectangular Parts.
Next, we proceed to the assembly of the tower from rectangular parts and organic transparent glass.
For mounting and additional rigidity of the rectangular parts of the tower I will use two m4 studs.
Plastic bushings of 5 mm height are installed for the distance between the parts.
Step 10: Assembled Device.
Step 11: End of Instruction.
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