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Using LM358 IC for Dual VU-Dial Indicator System in Plastic Housing: Tips & Tricks

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  • #91 19675258
    olaf x
    Level 34  
    I will not give you a hint here, I do not use any program when designing tiles.
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  • #92 19675377
    398216 Usunięty
    Level 43  
    I don't know about Kickad, but in Eagle you can do it in two ways; or by selecting the JUMPER item from the library and selecting the appropriate length element in it. Another option is to go to the other side of the path (elements) - it is good to determine the size of the via and its diameter right away.
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  • #93 19675484
    homo_sapiens
    Level 23  
    elektronik.b wrote:
    And how to make a jumper in kicad? because I read here on the forum and also on another that it is impossible to make a jumper in this program.

    KiCad's symbol libraries contain several jumpers. On the other hand, you select the footprint from the "Wire_connections_bridges" library and adjust the dimensions of the pads to your needs (the footprint length does not change).
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  • #94 19675713
    yogi009
    Level 43  
    KiCad is so convenient that after selecting the so-called In the footprint, you can also edit the shape and size of the pads (and, if necessary, the size of the hole). This is what I like about this program.
  • #95 19704936
    Olkus
    Level 32  
    I put a version of the board with two indicator drivers on one PCB, maybe someone will need it ...
    One connection should be made underneath with a cable (marked in red in the second picture). There are also incorrect "-" and "+" markings next to the bridge, initially the PCB was to be powered from symmetrical DC voltage, I added the bridge then and I forgot to remove the markings. The thermal transfer file is now valid.

    Regards,
    AND.

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  • #96 19887317
    rosomak19
    Level 23  
    Do I know anyone where I can make a scale to an indicator? I have to change four values so that stupidity doesn't show.
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  • #97 19887330
    Sanjose
    Level 32  
    And what is this indicator? As a rule, the scales mounted in them are adapted to the magnetic system.
  • #98 19889056
    rosomak19
    Level 23  
    Nissei TN105 BW indicator
  • #99 21570029
    pcichomski
    Level 16  
    zgierzman wrote:
    398216 Usunięty wrote:
    You can see why?
    .



    And does toto have logarithmic characteristics? "I don't think so", but I'm not concentrating on that, it's bedtime, after all the weekend is for rest. Maybe the diodes in the feedback break it down a bit to make the nodding of the cues look more believable?

    Electronic schematic with power supply, four TL084D op-amps, several resistors, capacitors, and diodes.



    There is no logarithmic characteristic because diode D2 inverted and the last amplifier works as a simple linear inverting rather than logarithmic.
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Topic summary

The discussion centers on a DIY dual VU-dial indicator system using LM358 operational amplifiers housed in plastic enclosures. The original design employs two separate PCBs with half of each LM358 chip used per channel, though it is suggested to consolidate both channels on a single PCB utilizing the full dual op-amp to reduce size and wiring complexity. The indicators are illuminated by front-facing LEDs, which many recommend replacing or covering to mimic original backlit designs for better visual comfort and authenticity. Calibration and scaling issues are noted, with the indicators often saturating near maximum deflection and lacking proper logarithmic response. Several contributors propose adding diode and resistor networks to improve linearity and dynamic response, referencing existing proven control modules and circuits, including those based on TL084 J-FET op-amps for better performance. Power supply considerations include symmetrical versus single 12V supply configurations, with suggestions for using Delon doubler rectifier circuits and appropriate diode (1N4007) and capacitor (≥100µF) values for filtering. PCB layout improvements focus on minimizing track lengths, using jumpers, and considering THT versus SMD components based on soldering skill and size constraints. The frequency response of the LM358-based amplifier was tested from 20Hz to 20kHz, showing consistent indicator deflection except for anomalies below 20Hz, indicating limited suitability of LM358 for precise VU metering. The community encourages iterative design refinement, calibration against known signal levels (e.g., 0 dB at 0.775V), and learning through schematic and PCB design tools like KiCad or Eagle. The Nissei TN105 BW indicator is mentioned as a specific meter model requiring scale adjustments. Overall, the project is recognized as a functional but basic audio level visualization device rather than a professional metering instrument.
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