Electronic systems temperature monitoring to protect from overheating

Published by g.karthick in the blog g.karthick's blog. Views: 226


Introduction
Overheating causes potential damage to the circuit components, and can cause fire, explosion, or injury. Power dissipation performance must be well understood prior to integrating devices on a printed-circuit board (PCB) to ensure that any given device is operated within its defined temperature limits. When a device is running, it consumes electrical energy that is transformed into heat. The first and most important thing you need to do when your devices are overheating is to clean the fan(s) that provide(s) cooling to the CPU and graphics card. Devices that severely overheat causes damage to the internal components. Before this happens, the devices should attempt to shutdown itself when it reach the threshold limit once cooling down again it can restart. To instruct the device performance we need a sensor to sense and indicate whether the temperature is reached to critical position or not. MAX31865Ev Kit RTD sensor is placed closer to the heating circuit to measure the temperature and cooling fans speed can be controlled based on the heat generated by the circuit devices. If the temperature exceeds the critical limits then RTD sensor can recommend to shutdown the system temporarily and again restart once the system is cooled to the desired level. I am using RTd sensor data to alert me when my system is overheating due to its continuous performance so that the system may not be damaged.

BOM
List of parts required for project are:
  1. MAX31865 Ev Kit.
  2. RTD temperature sensor with 1Kohms.
  3. Extension wire of length 2 meters.
SCHEMATICS:
The schematic diagram to record data from the sensor and convert it to digital data using on-board 16-bit ADC in max31865 chip.
[​IMG]

Figure 1: Schematic diagram for RTD connected to MAX31865 chip.
[​IMG]

Figure 2: Schematic diagram for SPI-to-USB converter circuit.

Procedure to install and connected hardware to GUI for MAX31865 Evaluation Kit:
The RTD sensor is connected to the MAX31865 Ev Kit, Follow the steps below to verify board operation:
1) Verify the two jumper wires (included) are properly secured in the terminal block in accordance with the 2-wire RTD Sensor Connector diagram on the PCB’s silkscreen.
2) Verify the 1kΩ resistor is properly secured in the terminal block connecting the RTDIN+ terminal to the RTDIN- terminal.
3) Set the EV kit hardware on a nonconductive surface that ensures that nothing on the PCB gets shorted to the workspace.
4) Prior to starting the GUI, connect the EV kit hardware to a PC using the supplied mini-USB cable, or equivalent. The POWER LED (D20) should be green and the COM LED (D21) should be red and slowly flash orange.
5) Windows should automatically begin installing the necessary device driver. The USB interface of the EV kit hardware is configured as a HID device and therefore does not require a unique/custom device driver. Once the driver installation is complete, a Windows message appears near the System Icon
menu indicating that the hardware is ready to use. Do not attempt to run the GUI prior to this message. If you try to run the GUI prior to this message, close the application and restart it once the driver installation is complete. On some versions of Windows, administrator privileges may be required to install the USB device.
6) Once the device driver installation is complete, visit www.maximintegrated.com/MAX31865evkit to download the latest version of the EV kit software,
MAX31865EVKitSoftwareInstall.ZIP. Save the EV kit software to a temporary folder.
7) Open the .ZIP file and double click the .EXE file to run the installer. A message box stating “The publisher could not be verified. Are you sure you want to run this software?” may appear. If so, click Yes.
8) The installer GUI appears. Click Next and then Install. Once complete, click Close.
9) Go to Start >> All Programs. Look for the MAX31865EVKitSoftware folder and click on MAX31865EVKitSoftware.EXE inside the folder.
10) When the GUI appears, the text below the Maxim Integrated logo should indicate that the EV kit hardware is connected. The COM LED (D21) turns off and flashes red when communication occurs.[​IMG]
Figure: GUI for the MAX31865 Ev Kit to record and save the temperature data.

Source code for the MAX31865 chip to monitor and record temperature data:
/****************************************************************************
MAX31865 Evaluation Kit program for Soil temperature monitoring.
****************************************************************************/
#include <SPI.h>
#include <MAX31865.h>
#define RTD_CS_PIN 10
MAX31865_RTD rtd( MAX31865_RTD::RTD_PT100, RTD_CS_PIN );
void setup()
{
Serial.begin( 115200 );
/* Initialize SPI communication. */
SPI.begin( );
SPI.setClockDivider( SPI_CLOCK_DIV16 );
SPI.setDataMode( SPI_MODE3 );
/* Allow the MAX31865 to warm up. */
delay( 100 );
rtd.configure( true, true, false, true, MAX31865_FAULT_DETECTION_NONE,
true, true, 0x0000, 0x7fff );
}
void loop()
{
rtd.read_all( );
if( rtd.status( ) == 0 )
{
double temperature = rtd.temperature( );
Serial.print( " T = ");
Serial.print( temperature, 1 );
Serial.println(" deg C" );
}
else
{
Serial.print( "RTD fault register: " );
Serial.print( rtd.status( ) );
Serial.print( ": " );
if( rtd.status( ) & MAX31865_FAULT_HIGH_THRESHOLD )
{
Serial.println( "RTD high threshold exceeded" );
}
else if( rtd.status( ) & MAX31865_FAULT_LOW_THRESHOLD )
{
Serial.println( "RTD low threshold exceeded" );
}
else if( rtd.status( ) & MAX31865_FAULT_REFIN )
{
Serial.println( "REFIN- > 0.85 x V_BIAS" );
}
else if( rtd.status( ) & MAX31865_FAULT_REFIN_FORCE )
{
Serial.println( "REFIN- < 0.85 x V_BIAS, FORCE- open" );
}
else if( rtd.status( ) & MAX31865_FAULT_RTDIN_FORCE )
{
Serial.println( "RTDIN- < 0.85 x V_BIAS, FORCE- open" );
}
else if( rtd.status( ) & MAX31865_FAULT_VOLTAGE )
{
Serial.println( "Overvoltage or Undervoltage fault occured");
}
else
{
Serial.println( "Fault exist; Please check connection" );
}
}
delay( 3000 );
}
Details of more source code can be cloned from the URL: https://github.com/hallard/arduino-max31865

Instructions
  1. Initially connect the 2-wire RTD sensor to the RTD port by replacing the 1kohm resistor in the Evaluation Kit.
  2. Plug-in the USB cable to the PC and evaluation kit then open the GUI software which shows the EV kit hardware is connected.
  3. ON the conversion mode, VBIAS, set to 2-wire RTD connection if red bubble in fault status indicates their is open connection in the RTD sensor or in-appropriate sensor connected.
  4. If all is set then start to measure the data from the chosen environment.
  5. In the current project we are going to measure the Electronic System temperature to protect from overheating.
  6. We placed the RTD temperature Sensor closer to the heating system to measure the temperature it was liberating during the function.
  7. The data recordings were saved in separate file to do further analysis and undergoes system maintenance.
System temperature data plot showing heating:
Electronic system.png

Video
Video show how to measure the temperature of the system where overheating is happen.


Improvement required for best utilization:

  1. If WiFi/ Bluetooth connectivity is available then it is easy for the user to utilize the kit for remote accessing the data from the measuring environment.
  2. An android app for smartphone will be a handy and helps to share the data and monitor in real-time.
Conclusion
The temperature of the system is measured to fined out the heating effect in current time. If the system is overheating it is better to go for maintenance in-time. MAX31865 evaluation kit helps to record the data and analysis is carried out to find that the system heating is happening in short time when it was switched ON. The results shows the MAX31865 evaluation kit is suitable to measure accurate temperature which helps to undergo maintenance in-time to protect the electronic system in our Home or Office.
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