I wanted a smart LED light for my son so he could read in bed at night and I could turn it off remotely. The problem with it was at minimum brightness was still too bright so I want to find a way to make it duller.
The PCB is a single sided aluminum clad looks to be less than 1mm.
The driver chip from the 2 LED strings is BP5778 J8D23VE. I couldn’t find a datasheet but did find an extract of the block diagram from one I found here
The 2 resistors RCS1=RA1 = 24R 1206 3×1.5mm 0.125 (1/8)W RCS2=RA2=24R 0805 2×1.3 0.1(1/10)W I assume are feedback resistors for current sensing. The different package sizes I assume are because of the different volt drop across the LEDSs enable the manufacturer to put in a smaller cheaper resistor for the lower volt drop so a lower power dissipation. I figure if I put in 240R resistors it will scale the brightness down to 1/10th.
This looks like the manufacturer of the chip but they don’t have a listing for it so it must be an OEM version only. http://www.bpsemi.com.cn/uploads/file/20181017105105_356.pdf
Without measuring the input voltage to the LED strings and the LED controller I assume there is at least 35V powering it. This means the PSU on the board is supplying 3.3V(ESP), 12V(colour unpopulated LEDs)and 35V(White LEDs). As I am not dismantling this now I’ll have to check it out another day to confirm what it does to achieve this.
TYWE3L is the ESP8266 WiFi chip that has a RTOS system on it. A quick look at the spec also says it can operate at over 100degC
https://developer.tuya.com/en/docs/iot/wifie3lpinmodule?id=K9605uj1ar87n
http://m.elecfans.com/article/583763.html
The housing is made of aluminum which I think is both a heatsink and mainly a RF shield to stop all the switching noise escaping.
Lamp VIN measured 321V (rectified 240VAC) and 12V measured 13.4V. The LEDs measured 184V inner string cool/white and 190V inner warm/yellow at 1%.
16 LEDs in each string equals about 12V per LED at this brightness and will be a little more for full brightness
RA1 measured 12.6VAC but it think it possibly could be switching noise.
I changed the SMT resistors for 220R versions
Powering it up it is now scaled down to a duller brightness which is perfect
So I turned a 10W light into a 1W max light assuming the controller is linear based on the feed back resistance
