Very new to electronics outside base knowledge.

This board is from a small smartphone toy, where pressing and holding the button displays 1 color on an attached RGB LED and quickly double tapping the same button changes it to another fixed color. There's no way (on board) to cycle through the various color values, it's just a hard change between different values.

I'm trying to build my own circuit that does the same thing, but I'm not sure what that IC is below the push button. There's no text on it or even an image, so I can't look up the data sheet. Searching the silkscreened "TLBZ-039-V2.0" also yielded no results. My first thought was that it was a generic 555 chip because all it has to do is change the voltage going to the different pads, but all the datasheets I've found for a 555 chip show pin 1 is GND and on this board, it has pin 1 being VCC.

Without taking the IC off the board it also looks like pins 2 and 3 just aren't used, or they disappear somewhere beneath the chip. I can post more pictures of the bare board with the traces once I get the button/IC off.

Picture of a round circuit board showing 1 capacitor of unknown size, 3 resistors, an unknown IC chip, a single push button and 4 contacts for an RGB LED

  • 3
    \$\begingroup\$ Try to get more brightness on the IC in the photo, if you have control of your cameras exposure settings go up 3 or 4 steps on the time or aperture. if not cover everything else with black paper and use a bright light. \$\endgroup\$ Sep 24, 2020 at 8:11
  • \$\begingroup\$ I don't think the hidden traces do anything interesting. \$\endgroup\$ Sep 24, 2020 at 8:15
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    \$\begingroup\$ It's probably a simple 8-bit MCU like a cheap 12F PIC or similar. Its also possible its a custom IC if they're manufactured in hundreds of thousands. \$\endgroup\$ Sep 24, 2020 at 8:16
  • \$\begingroup\$ Do you have a scope to probe around the pins. Are there any components apart from R1-3, C1, the switch and the IC. Are the 4 wires on the right going to the LED. It could just be triggering on the switch and cycling through pins 4, 5 and 6. I would guess it's a simple TTL/CMOS chip setup rather than anything fancy. It could be a custom chip but that might be cost prohibitive. If it's a processor then it'll need a clock. \$\endgroup\$
    – mhaselup
    Sep 24, 2020 at 8:17
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    \$\begingroup\$ 1) it's from a toy (so must be cheap) 2) 8 pins 3) some buttons, LEDs very few resistors and a capacitor: that's what 95% of electronics in toys etc. use, a cheap microcontroller. These can be bought for around 3 cents when you buy enough of them. See: youtube.com/watch?v=VYhAGnsnO7w There simply is no cheaper solution so all manufacturers use a cheap uC like this. \$\endgroup\$ Sep 24, 2020 at 8:20

4 Answers 4


A 555 can't simply do what that chip does, so it's not a 555.

It is most likely a cheap microcontroller that runs a button-reading LED-blinking program to make it work. Or a specific chip made for these kind of products, but a microcontroller allows to just use one chip for all kinds of different products.

  • \$\begingroup\$ The 555 kept coming up when I looked for "8 pin icu" and it was the closest datasheet I managed to find but the reversed polarity on pins 1/8 made me think it wasn't so thank you for confirming my suspicion. \$\endgroup\$
    – T. Cubbin
    Sep 24, 2020 at 10:01
  • \$\begingroup\$ What's an "icu"? \$\endgroup\$
    – Justme
    Sep 24, 2020 at 12:00
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    \$\begingroup\$ @Justme It's where the critically ill patients go at a hospital (intensive care unit). :) Maybe it's a typo of "MCU". \$\endgroup\$
    – JYelton
    Sep 24, 2020 at 15:10
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    \$\begingroup\$ @JYelton I think it's a typo of "IC" \$\endgroup\$ Sep 24, 2020 at 16:38
  • \$\begingroup\$ @user253751 Ah, yep, much more likely. \$\endgroup\$
    – JYelton
    Sep 24, 2020 at 16:44

It's probably a simple 8-bit MCU like a cheap 12F PIC or similar. It's also possible it's a custom IC if they're manufactured in hundreds of thousands.

If you are simply trying to recreate the behaviour, pick any little microcontroller (e.g. PIC or ATTiny) and program in the behaviour you want.

  • \$\begingroup\$ I recommend a PICAXE if you are new. It helps shield you from a bunch of the setup and programming complexity. Makes things a lot less daunting. \$\endgroup\$
    – DKNguyen
    Sep 24, 2020 at 23:18

Put the board in the freezer for 30 minutes then when you pull it out, as it thaws often you will see the outline of any markings that were removed. My suspicion is it's one of those 2-5 cent controllers EEvblog wrote about

  • 1
    \$\begingroup\$ +1, the VCC and GND locations match the "3 cent microcontroller" PMS150 \$\endgroup\$
    – jpa
    Sep 25, 2020 at 9:53

I'm trying to build my own circuit that does the same thing ...

As already written, the IC is either a microcontroller or a custom IC.

If it is a custom IC, you have no chance to get the same IC and you have to use a microcontroller (price: about 1 Euro or 1 US-Dollar plus about 30 Euros/Dollars for a programming device) if you want to build such a device yourself.

If you want to use the same pin-out as the IC on the photo: the ATtiny 102/104 ICs have that pin-out.

However, it requires a lot of programming knowledge to program such a controller, and using an ATtiny 10x programming will be a bit tricky if pin 4 is used because a programmer with a four-state (0V, Vcc, 12V, High-Impedance) output signal is required.

I doubt that cheap programmers have four-state output signals, so a more expensive programmer would be required.

Using pin 2 or 3 instead of pin 4 would make programming easier because only binary output signals are required if pin 4 is not used.

If you can use a chip with another pin-out (maybe with more pins), I would take a larger controller which can be programmed in a high-level language. There are 8-pin 32-bit Cortex controllers that can be programmed in C, C++ and other programming languages.

I know based on my very limited knowledge of RGB LEDs that it's just sending different voltage values out through pins 5, 6, and 7 which cause the LED to make different colors.

Such a "color LED" is actually three LEDs: A red one, a green one and a blue one.

If you want yellow, you switch on the green LED and the red one and you switch off the blue one.

As already written, you would not use different currents (and in no way different voltages) to change the brightness of the LED. Instead, you use PWM: You switch an LED on for 10 milliseconds and switch it off for 30 milliseconds, you switch it on again for 10 milliseconds and so on...

The human eye will not perceive this as "blinking" but as 25% brightness.

  • \$\begingroup\$ 10ms on and 30ms off means 40ms PWM period which is 25 Hz. I know different people have different flicker fusion threshold, but I think even average person would find that 25 Hz blinks annoingly instead of perceiving it as 25% brightness, especially if the light moves or the PWM-illuminated scenery moves (e.g. riding a bike). \$\endgroup\$
    – Justme
    Sep 25, 2020 at 8:29

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