OpenLF Controller


OpenLF stands for "open led and fan". Its a controller that will monitor led current(max current 6A) and control brightness. It also includes a independent 3 Wire fan controller IC with option to read RPM and adjust the fan's speed. In the design one status led and a button is also present which can be configured for future purposes. An additional i2c header is also present which can be further extended to use external 2 wire peripherals like an OLED. The fan speed and led brightness can be externally set by two potentiometers.


The heart of the project is Attiny1614 which can be programmed with UPDI Programmer. The source code of the programmer can be found here. The arduino core for the MCU can be found here. It has 16384 bytes flash, 2048 bytes RAM and 256bytes EEPROM on-board which makes it suitable for this project. The major reasons for choosing this IC over others are as follows:

  • Cheap,
  • small footprint and available in solder-friendly SOIC package
  • internal clock configuration support upto 20MHz.

Major Peripherals

  • MAX6650 - The fan controller ic MAX6650 which is connected to the MCU via I2C. It can regulate and monitor the speed of 5VDC/12VDC brushless fans with built-in tachometers. They automatically force the fan’s tachometer frequency (fan speed) to match a pre-programmed value in the Fan-Speed Register by using an external MOSFET or bipolar transistor to linearly regulate the voltage across the fan.
  • INA226 - It is a current shunt and power monitor with common-mode voltage upto 36V controlled by I2C. It has programmable conversion times for both the shunt voltage and bus voltage measurements which makes it easy to be configured to optimize the available timing requirements in a given application. This is used to measure the current consumed by the attached led and thus provide feeback loop to the mcu to adjust PWM accordingly.


The controller can be used in multiple led applications where DC side dimming is required for example, adjusting brightness of a led back-lit panel used in photography and videography. User can get details of power consumption of the led displayed on OLED. The external header for UART can be used for debugging or talk to other wireless microcontrollers for remote operation.

Please note, this is a initial release and may not have enough features.

Further improvements may include wireless mcu like ESP8266, efficient buck converter for lowering power loss, etc.

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