https://www.epanorama.net/blog/2025/05/27/touch-switch/ All about electronics and circuit design Thu, 23 Apr 2026 12:41:17 +0000 hourly 1 http://wordpress.org/?v=3.9.14 https://www.epanorama.net/blog/2025/05/27/touch-switch/comment-page-1/#comment-1867801 Tue, 30 Dec 2025 15:22:49 +0000 https://www.epanorama.net/blog/?p=197875#comment-1867801 Touch switch
https://youtu.be/lKN9Xs4_S4g?si=7MO3GFsPCHVz1C_D

]]> https://www.epanorama.net/blog/2025/05/27/touch-switch/comment-page-1/#comment-1865688 Thu, 20 Nov 2025 17:54:26 +0000 https://www.epanorama.net/blog/?p=197875#comment-1865688 MOSFETs are highly sensitive to ESD because of the thin layer of silicon dioxide that insulates the gate, which can be damaged by voltage spikes that exceed its breakdown voltage. Always use an anti-static workbench and wrist strap when handling bare MOSFETs. This circuit is pushing ESD directly from finger to FET.

]]> https://www.epanorama.net/blog/2025/05/27/touch-switch/comment-page-1/#comment-1865027 Sun, 09 Nov 2025 08:49:39 +0000 https://www.epanorama.net/blog/?p=197875#comment-1865027 The fix: Add protection like 15V zener diodes that keep G-S gate voltage at safe level.
I would also add a series resistor from user input to zener.

]]> https://www.epanorama.net/blog/2025/05/27/touch-switch/comment-page-1/#comment-1865026 Sun, 09 Nov 2025 08:46:37 +0000 https://www.epanorama.net/blog/?p=197875#comment-1865026 MOSFETs are very sensitive to electrostatic charges and can be easily damaged by them. Here every touch sends smaller or bigger ESD pulse through diode to MOSFET gate. If gate voltage rises to too high voltage, MOSFET is fried. The IRFZ44N has a maximum gate-to-source voltage (VGS) of ±20V. Exceeding this limit can damage the component. The ESD pulse from person touching can easily be hundreds of volts or even several kilovolts.

]]> https://www.epanorama.net/blog/2025/05/27/touch-switch/comment-page-1/#comment-1862648 Mon, 29 Sep 2025 10:16:20 +0000 https://www.epanorama.net/blog/?p=197875#comment-1862648 This looks like a recipe to try to kill the mosfet!
Mosfets are ESD sensitive devices, and in this circuit you feed the ESD from user to device gate.

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