Multichannel Temperature logger
I present here a six channel temperature data logger. The unit uses the DS18B20 digital temperature sensors. It also has a Real Time Clock (RTC-DS1307). The RTC supplies the time stamp for the logged data. A 4x4 numeric is used for setting the time/date and the logging interval. The keypad is also used to start/stop the logging. I also use a 4x20 LCD to display the current time/date instantaneous temperature from one of the sensors. An SD/MMC is used for saving the logged data. Due to the temperature resolution of the sensors +-0.5oC and the min. logging time of 1sec. this logger is most suitable for environmental monitoring. The unit was build around the Microchip PIC18F420 microcontroller and the code was written using PIC MIKROC from MikroelektroniKa. For test I used the easypic6 development board from Mikroelektronika, their RTC2, and the MMC/SD board. http://www.mikroe.com/eng/products/view/138/mmc-sd-board/ http://www.mikroe.com/eng/products/view/197/rtc2-board/ http://www.mikroe.com/eng/products/view/297/easypic6-development-system/ The code, schematics and latter a pcb design is included.
Currently the unit uses an external DC power source and the 7805 regulator to supply current to the unit. I think for the unit to be more useful it is better to re-design the unit to use AA batteries. I think the best is to use DC-DC step up convertor IC. I will be very nice to have ideas about such addition to the logger circuit.
I am now having a PCB layout for the project. I hope that I will soon get the PCB's made and then fully test the layout.
The first unit was build to monitor the temperature variation at different points in a concrete slap just after the concrete was molded and during hardening. That was for an M.Eng. student. The unit was very primitive it only had the keypad and the LCD. The logging was done manually every few hours for a couple of days.