I would like to learn how to build a standalone circuit that allows me to flick through several LED states (on/high/low/off, etc.) without something like an Arduino.

I'm new to electronics and have decided to learn by examining simple, existing circuits. Today I opened up a cheap LED tent lamp. It has a single button to control it. Each click cycles through various states. From the off state, these are:

  • First click: White LED On - Max Brightness
  • Second click: White LED On - Half Brightness
  • Third click: Red LED On (White LED off)
  • Fourth click: Off

I've attached a picture of the circuit board inside the lamp. It's hard to tell if pins 1-3 of the IC are connected to anything, which just adds to my difficulty understanding what's going on here.

The bit I'm holding on to is the push switch. Pin 1 of the IC is in the top right corner. The transistors are J3Y transistors. The component right beside pin 4 is a diode with the cathode on pin 4 side.

LED tent lamp circuit board

If you could please advise:

  • how this circuit works;
  • what the IC is or could be (it's unlabelled so I couldn't find a datasheet anywhere); or
  • any other options I might have in replicating the functionality described above!


  • \$\begingroup\$ Realistically, you use something like an Arduino, but not the entire Arduino, just the main chip. That really is the easiest way to build a circuit like this. \$\endgroup\$
    – user253751
    Jul 17, 2020 at 13:32
  • \$\begingroup\$ the chip pinout seems to match an ATtiny85 ... learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/… ... the two PWM outputs drive the transistors \$\endgroup\$
    – jsotola
    Jul 17, 2020 at 16:32

1 Answer 1


The chip is either a specially made IC that does all of the functions in hardware, or it is a small microprocessor programmed to carry the the described functions.

Your options are to build similar hardware out of standard logic ICs, or to program a small microcontroller to carry out the functions you want.

Either option will be bulkier and more complicated than what you are looking at.

If you build it out of standard logic ICs, it will take at least a couple of ICs and some other parts.

If you go the microcontroller route, you'll probably have to add in a couple of transistors to help the controller deliver enough current to the LEDs.

If you go the hardware way, you'll learn more about logic and electronics and zero about microcontrollers and programming.

If you go the microcontroller route, you'll learn a bit about logic, a bit about programming, and a bit about electronics.


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