Light & Time Switcher Arduino project

This project switches the heating lamps for my two tortoises. It replaces an clunky contraption based on a Landis & Gyr Visogyr with two reverse engineered modules and running a Colbas program. The actual mains switching is a separate box, which might be described later.

Board, top view The LTS controls a relay based on both time and light. The relay is switched on if both the time is later than the morning time stamp and the light level is above the on-light level. The relay is swiched off if both the time is later than the evening time stamp and the light level is below the off-light level.

The device needs an Arduino compatible power supply, a LDR for light measurements. The relay is used to close a secondary low voltage curcuit which switched a solid-state relay. This relay switches mains power for

All control of the parameters is done via the serial port on the USB interface.

This is an image of the the second prototype. Oversized for the component count, but the width is for the case slot. There are no plans to make an etched board.

Diagram/schema Not much external hardware, a relay, DS1307 RTC and two LEDs. Even for a shield, a modest number of components.

The software is developed with the Arduino IDE 0022 on Kubuntu 10.10/x86-64. It fits in the memory footprint of the ATMega168, runs on an Arduino Diecimila. I assume it is compatible with newer Arduino boards.

The DS1307 is controlled using the DS1307new library.

Mounted in
the case
Maybe later I will add a real nice front.
On top are the connections to the LTS. Below is a simplified version of the mains power switch.
If I would design the whole system now from scratch, the LTS circuit would probably activate the solid state relay directly and leave out the secondary 12 V circuit.

Last updated: 2011-10-03