How does this work? 4-Mode LED Lights, Flashing without transistors or resistors.

Thread Starter

ethanhberkey

Joined Dec 23, 2021
2
Hello i'm interested to know if anyone has expertise on how this little device works. I'm particularly intrigued as to how such a small PCB can produce 4 different channels of light and 2 flashing red LEDs with no transistors? I've posted some images. I would like to know how i could recreate this.

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dl324

Joined Mar 30, 2015
14,324
Welcome to AAC!
I'm particularly intrigued as to how such a small PCB can produce 4 different channels of light and 2 flashing red LEDs with no transistors?
It isn't possible. They make LEDs with a microcontroller in the encapsulation. What does the switch do?
 

Thread Starter

ethanhberkey

Joined Dec 23, 2021
2
Welcome to AAC!
It isn't possible. They make LEDs with a microcontroller in the encapsulation. What does the switch do?
No microcontrollers to be found. I disconnected the LED and tested it with a resistor, didn't blink. I've actually identified what seems to be a micro sized transistor in the RED LED circuit. Looks comparable to a CPU transistor. See the image. I'm just surprised that they make transistors that small. That's a button, and it changes the modes between levels 1-3 of brightness and the 4th is red flashing on sides. It also turns it off.
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Last edited:

ronsimpson

Joined Oct 7, 2019
2,011
Look carefully at the white dot. Under the paint there is a silicon chip. There are 9 traces of copper connected to it. It might be a micro controller but I think it is a micro sequencer which is even more simple. I have built boards like this. There are several ICs that are used to make LEDs flash and blink. The ones I used had a timer and a small block of ROM memory. In the factory you program the memory with a sequence of up to a 64 long. A resistor sets how fast the clock advances. There were some commands to set the duty cycle on the pins. (if you want more information, ask, don't want to say too much now) I made one of these ICs drive some RGB LEDs and run through 60 different colors. You might have seen balls that blink colors when played with. Also light on toy fire trucks. (did toys for a while lol)

example of memory:

00000000 all pins are low
00000100 one pin is high
11111011 one pin is low
11111011 same thing as above but makes it look twice as long.
10101010 half of the pins are low
11111111 end of pattern, jump back to start.
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SamR

Joined Mar 19, 2019
4,130
Yup, I've been seeing a lot of those custom jobs hidden under a spot lately. Not even a chip, all on a pretty much bare wafer with a dab of conformal paste to protect it.
 

ronsimpson

Joined Oct 7, 2019
2,011
COB "Chip On Board". In this example they could get the IC in a 44 pin package but they chose to get just the silicon and wire bond to the PCB. Then a covering must be applied to keep air off the silicon and the wires are very fragile.
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One 1000 words:
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