Sunday, December 9, 2018

RTC based automatic LED lamp

This is real-time clock based automatic LED lamp which we originally designed to use as night light. This lamp can programmed to turn on and off at the specific time of the day. For example, it can program to turn on at 6 PM on each day and to turn off at 4 AM next day.

The core component of this project is PIC16F883 MCU and it's firmware is developed using MikroC Pro for PIC. We select this MCU because of it's 7 KB flash memory, I2C, UART, E2PROM and built-in 8-bit and 16-bit timers. In this system we use DS1307 RTC because of it's availability in the market and lower external component count.

Prototype version of RTC Lamp

This lamp is designed to work with commonly available 7W LED panels. In our prototype design we use 7W 24V warm-white LED module to test this system. To drive other LED modules change value of the R5 resistor of the current limiter circuit.

This system is designed to program using RS232 serial port. User can modify system time, light start and end times by connecting this system to any computer through RS232 serial port. To program and view system information user can use any serial terminal application like minicom, putty, etc.

Once system is connected to the host PC it can switch to programming mode by sending Enter or Space key stroke through the serial terminal.

This unit is designed to work with 24V - 3A power supply unit. 3V button cell is required as back power source of DS1307 RTC. Supplied PCB is designed to work with CR2025 or CR2032 type button cells. 

Final view of prototype model

For this project we use commonly available, less expensive electronic components and in PCB design we use all "through-hole" type components. LED module, heat-sink and lamp enclosures are now commonly available in the market but make sure to use good quality 24V - 28V LED module with this circuit. During our prototype we found lot of defective LED modules in the market.

This is an open hardware project and all it's source code are released under the terms of MIT license. Schematics, PCB designs and other resources are released under the terms of Creative Commons Attribution 4.0 international license. All the source codes, design files and build instructions are at github repository.

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