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I have a TM1638 board with 8 seven-segment displays, 8 LEDS, and 8 buttons. Each time multiples leds are on, the board makes an annoying high pitch sound.

I'm controlling it with an Arduino Uno.

Should I worry about the sound and is it normal?

This is my board :

enter image description here

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  • What board do you have?
    – Majenko
    Aug 7, 2018 at 15:13
  • check your ground connections
    – Chad G
    Aug 7, 2018 at 18:08
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    Where does the sound come from exactly? When your LEDs are on, they draw power from the power supply. Cheap switching power supplies will exhibit a ringing sound under load (Spulenfiepen / coil whining, en.wikipedia.org/wiki/…) Aug 7, 2018 at 19:37
  • I would guess it is a harmonic from the multiplex signal. Touch each part with a pencil eraser and see if it goes away. Can you change the voltage by maybe 0.02 volts and see if it changes. Without a schematic I can only guess. I have seen these symptoms before but not with this hardware.
    – Gil
    Mar 26, 2021 at 22:02

1 Answer 1

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This thread is getting old but this LED&KEY device seems to still be fairly popular so this may still help someone else. I'm using one to control a radio receiver and the constant buzz can get pretty loud.

I found this article (A second look at the TM1638 LED & key controller) which mentions the same issue which was solved by inserting a 100Ω resistor between VCC and the VCC pin. I also added a 1000μF electrolytic capacitor across the VCC and GND pins (well, fairly close to them anyway). This quieted down the buzz a lot though it's still there. The resistor is key though the capacitor helps a bit.

I also tried moving the breadboard connections to a separate, smaller breadboard, away from the MCU and radio receiver chip and was able to use lower values (10Ω and 47μF). I was no longer able to hear the buzz at all.

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