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  1. #1
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    Electromagnetic interferences - how to handle?

    Hi everyone,

    I'm working on a little DIY lamp project with a capacitive switch.
    The kit consists of a breadboard with some components, a battery and its charging PCB, and a 20cm-long electric wire that leads to the aluminium foil used as capacitive sensor.

    The lamp switch on and off randomly when in proximity of things, particularly as it nears other electronic devices.
    I believe this is due to electromagnetic interferences (EMI) affecting the electronic components.


    I'm wondering how I could fix the problem. I know EMC is a bit of black magic, but perhaps there are simple steps to address the issue, at least partially?
    I don't think I'm confident enough to delve into active shielding, so I'm looking for simpler passive options. Perhaps someone can help me find a good solution?

    Would it work to wrap my breadboard with aluminium foil?
    Is it possible to use a shielded cable for the 20cm cable leading to the capacitive sensor (aluminium foil)?
    Also, I have found electronic PCB using capacitive switches. Some parts seem to be covered with a yellow paste. Could this paste be a shield? Could I use something similar?



    Thanks in advance for your help!

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  2. #2
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    Re: Electromagnetic interferences - how to handle?

    First things first, you shouldn't use breadboards for such sensitive circuits and systems, it's worst choice for them.
    EMI can have internal sources as well as external ones.In order to distinguish, you can make some tests like shielding signal carrying cables,shielding around sensitive components,using an enclosure for whole system..etc.The main examination is done by observing signals and power supply lines.It's really hard to find to the exact cause but no way ..Even the GND itself can be a real troublesome cause..



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    Re: Electromagnetic interferences - how to handle?

    Without knowing exactly what the circuit is, it is difficult to make a more accurate guess, it may be for example that you have not connected anywhere a high impedance input, having a floating static voltage acting haphazardly.

    Anyway, if the interference occurs only due to the proximity of another circuit, it is also possible that your circuit is not correctly connected to the reference (0v). As stated above, breadboards are prone to capture emissions, as each hole is connected to internal metal rails, which can act as antennas; you can however reduce the effect of this by tying to the reference all unused trails in the vicinity of the circuit.
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