Hi guys, This is a temperature data logger consisting of a micro SD Card from eBay.The schematics, source code as well as the gerber files are below.The brain of this circuit is a ATMEGA 32. Datasheet - http://www.atmel.com/images/doc2503.pdf The temperature sensors are cheap LM35's and I am using 5 of them for input form 5 different sensors.As in the design of Mr.Dharmani,which provides support from 5 different sensors. Before I begin I highly recommend that you visit his site Link-- http://www.dharmanitech.com/2011/05/microsd-atmega32-datalogger.html ------------------------------------------------------------------------------------- Now let me explain to you the step by step function of each component. Starting up- 1)The Power Supply--It is a very simple linear power supply which provides fixed 5 V supply for the entire circuit.The part used is a simple LM7805.(One of the easiest to use components of any circuit). 2)The Op-Amps-- The opamps is a quad op amp as well as a dual opamp. I will do a tutorial on op-amps later.The Op-amps are LM324 and LM358. The op-amps are configured as buffers.See the figure below. A voltage buffer amplifier is used to transfer a voltage from a first circuit, having a high output impedance level, to a second circuit with a low input impedance level. The interposed buffer amplifier prevents the second circuit from loading the first circuit unacceptably and interfering with its desired operation. So a buffer op-amps are very easy to use and provide stability to the circuit and prevent unnecessary loading of the circuit. Let us assume a case where a a signal is generated from a source(say a sensor) but if we draw a significant amount of current from the source there will be a voltage drop which can cause several issues with the circuit(for example give wrong readings to the controller). 3--The Microcontroller The microcontroller is a ATMEGA32 for Atmel. Its functions are the following- 1. SPI Communication (b/w the uC and the SD card) 2. I2C Communication (b/w the uC and the DS1307 RTC) 3. ADC (Analog to Digital Communication for reading the value temperature sensor) 4. User Interface--A power LED and a user LED 4--The Real Time Clock The Real Time Clock (DS1307) Datasheet --http://datasheets.maximintegrated.com/en/ds/DS1307.pdf DS1307 time stamps each and every recording from the Sensor and saves it in the Micro SD Card in CSV Format. The DS1307 has a 3V Battery backup with it so incase of a power cutout the date and time does not have to be deleted. ------------------------------------------------------------------------------------- This project is yet to be tested,but you can still get the gerbers and schematic below but at your risk.However you should download the source code from the link--- http://www.dharmanitech.com/2011/05/microsd-atmega32-datalogger.html |
Gerber Files |
Schematic |
This Temperature Data Logger by Saptarshi Ghosh is licensed under
a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Based on a work at http://www.dharmanitech.com/2011/05/microsd-atmega32-datalogger.html.