Reverse engineering remote control outlet (relay circuit)

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Thread Starter


Joined Sep 13, 2019
Preface, I'm not an electronics noob, but this is just beyond my current understanding.

I bought some cheap remote control outlets from the usual source and I had the idea that I'd like to remove the existing remote control circuitry and replace it with an ESP-01, leaving the relay and mains voltage portions alone. I'm having a hard time reverse engineering the circuit, the relay bit seems strange. I've spent several hours in photoshop tracing out the circuit board with some high res photos and looking up as many datasheets as I can. I'll upload pics of the circuit board (I flipped the top side so the contacts would match). I've narrowed down that the IC on the left is a CY800 RF receiver, the other IC is clearly a microcontroller. Pin 8 of the CY800 is the digital output going into pin 2 of the uC, pin 3 of the uC goes to the base of an NPN transistor which switches one side of the relay coil to GND (from the full bridge rectifier). The other side of the coil is connected to + of the rectifier, the collector of another NPN transistor, and through a 5.6k resistor to the base, not sure why. There is also a cap between this + line and the + line that's feeding the uC, decoupling I imagine. I'm curious about the J6 transistor arrangement though, the resistor between the collector and base. I'm just short of plugging the thing into mains the poking around with a multimeter, but I figured I'd ask here first. Hopefully someone can help me understand.

Addendum: I guess I could just remove the uC and find some way to power an ESP-01, then give that NPN transistor (CR) a signal to switch the relay...but I need a solid 3.3v for the ESP. I'm pretty sure the uC is being run from the 5.1v zener diode you can see on the top side, I could use a 3.3v regulator from that 5.1v source right?



Joined Jan 29, 2010
hi Halo.
Welcome to AAC.
Unfortunately Transformer-less mains power supplies are not open for discussion on AAC, they can be lethal to an inexperienced person.
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