---
title: "Analyzing a no-neutral circuit"
date: 2024-02-15
---

https://www.openhardware.io/view/750/No-neutral-power-supplyrelay-board-for-in-wall-switch

want to inspect signals:
GND (bottom: COM pin)
L (bottom: L pin)
L1 (bottom: L1 pin)
N3_GATE (bottom: pin 3 of triac)
N4 (top: pin 4 of optocoupler)
N6_VIN (top: tab of regulator)
N7 (bottom: + output of U2 rectifier)
N16_OPTO_ONOFF (top: pin 1 of optocoupler)



try removing D10 (top power path), does it initially power on?
try removing D4 (bottom power path), does it initially power on?

try measuring DC voltage rail while the unit is booting, while it's doing zigbee transfers
try measuring chip VCC and N14_OUTPUT_ONOFF during bootup, what does the chip do?
try removing Z5, is there ever a voltage drop across triac's MT1..MT2? do R1/C1 turn it on?

measure current through R7

remove ZT4L from circuit, power it separately. what does it output on bootup? what does it output when the lamp is turned on? when lamp is turned off?

Analysis sheet: https://docs.google.com/spreadsheets/d/1Dn7bdnIEWB4b89QjrSKjqdJw3tgV5dlJC1IAV3ylBUY/edit

What is U3? It's Kiwi Instruments KP311ALGA!!!
       Similar: Fremont Micro Devices FT8430
       Similar: https://www.szlwtech.com/AP8003.html
       Similar: kiwi instruments KP3110

product link: https://www.aliexpress.us/item/1005005599808129.html


when the load output is OFF, the chip's N14 output is solid 0V

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