AUL-10 LM3915 BENCH
DUAL VU METER CALIBRATION CONSOLE • RASPBERRY PI 4
MAINS
POWER
[01] 1960s DUAL-TRACE CRT OSCILLOSCOPE
TIME / DIV
1.0 ms
VOLTS / DIV
0.5 V
TRIGGER LOCK
ZERO-X
[02] 9-BAND GRAPHIC EQUALIZER
0dB
63Hz
0dB
125Hz
0dB
250Hz
0dB
500Hz
0dB
1kHz
0dB
2kHz
0dB
4kHz
0dB
8kHz
0dB
16kHz
[03] AUDIO TONE GENERATOR
COARSE FREQ
440 Hz
DECADE MULT
×1.0
[04] MASTER LEVEL & CHANNEL ROUTING
MASTER VRMS
1.50 Vrms
BALANCE
CENTER
CH 1 (LEFT)
CH 2 (RIGHT)
DC PIN 5 DETECTOR
2.12 V DC
[05] AUL-10 LM3915 DUAL VU METERS
PIN 9 MODE:
LEFT CHANNEL (CH 1)
0.000 Vrms | -∞ dB
RIGHT CHANNEL (CH 2)
0.000 Vrms | -∞ dB
🛠️ HARDWARE TROUBLESHOOTING & CALIBRATION MANUAL (LM3915 / AUL-10)
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1. LM3915 Theoretical 3 dB Step Reference Table (1.50 Vrms Full-Scale)

When input sensitivity trimmers are calibrated for 1.50 Vrms at 0 dB, each LED segment corresponds to the following thresholds:

🔧 INTERACTIVE PCB TRIMMER POTENTIOMETER SIMULATOR

Use these sliders to simulate turning the multi-turn trimmers on your AUL-10 PCB kit:

2. Step-by-Step Trimmer Calibration Procedure

  1. Connect the Raspberry Pi 4 3.5mm audio output (or USB DAC) to the input of your AUL-10 VU meter boards.
  2. Turn ON the bench power switch. Select Sine wave, set frequency to 1 kHz, and turn Master Vrms to 1.50 Vrms (100%).
  3. Adjust the blue multi-turn trimmer potentiometer on each AUL-10 PCB until LED 10 (0 dB Red) just lights up solid.
  4. Step the Master Vrms knob down in 3 dB increments (e.g. 1.06V for -3 dB, 0.75V for -6 dB) and verify that the physical LEDs turn off sequentially.

3. MOD Jumper & Raspberry Pi USB Audio Isolation