Cold storage warehouse temperature monitoring device

The bulk storage of large or small quantities requires refrigeration that enables cold store facilities to be safe, energy conscious and maintain standards. Cold storage preserves agricultural products by eliminating sprouting, rotting and insect damage. The temperature necessary for preservation depends on the storage time required and the type of product. In order to know the temperature flow distribution map in the warehouse and to control at constant temperature we need a temperature sensor kit to record and visualize real-time data on the warehouse temperature. In our innovative design project Cold storage warehouse temperature monitoring we are going to choose “Maxim’s MAX31865 Evaluation Kit” because it has on-board ADC for RTD, mini-USB connecter to transfer data to the PC for data visualization in GUI. Digital temperature records can be maintained to carryout analysis for the storage time of food without perishes and energy loss. The monitoring of temperature with Maxim’s MAX31865 Evaluation Kit is easy and effective to maintain the warehouse temperature suitable and supportive for the different types of food items in different sections. A general rule for vegetables is that cool-season crops should be stored at cooler temperatures (32 to 35°F), and warm-season crops should be stored at warmer temperatures (45 to 55°F). These temperatures can be easily monitored and maintained using Maxim’s MAX31865 Evaluation Kit in the cold storage warehouses.

List of parts required for project are:
  1. MAX31865 Ev Kit.
  2. RTD temperature sensor with 1Kohms.
The schematic diagram to record data from the sensor and convert it to digital data using on-board 16-bit ADC in max31865 chip.

Figure 1: Schematic diagram for RTD connected to MAX31865 chip.

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

Procedure to install the GUI and connect Hardware:
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 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.

Source code:
* MAX31865 Evaluation Kit program for Solar Panel Temperature measurement.
#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" );
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");
Serial.println( "Fault exist; Please check connection" );
delay( 3000 );
The details of source code is in the following URL:

  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 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 well then start to measure the data from the chosen environment.
  5. In our present project we are going to measure the warehouse chiller Temperature which is useful to control the temperature of the cold storage products.
  6. We placed the RTD temperature Sensor in side the chiller to monitor the cooling process which keeps the temperature of the room to a level where we can store food items.
  7. The data shows the constant temperature in the graph as it was maintained at low temperatures.
Data plot showing the chiller maintained at low temperature:

Video shows how the maintains is performed to measure the temperature of water in the chiller.

Improvements required
  1. If multiple sensor are connected to the same kit for multiple recordings it would me more advantages to sense temperature at different placed of the room.
  2. Buzzer is needed to set to alarm for fault detection or when the temperature fall below the threshold level.
  3. If WiFi connectivity is add to the evaluation kit then it is easy for the user to utilize the kit for remote accessing the data from the measuring environment.
  4. An android app for data sensing is need to be designed for smartphone will help to share the data and monitor in real-time.
MAX31865 Ev Kit is helpful to measure the temperature of warehouse where we store food products. The on-board features of converting the temperature to 16-bit ADC gives the accurate value of the temperature. The software GUI will show the real-time graph and can save the data for further analysis. When the temperature of the warehouse is maintained in appropriate conditions then the food items can be store for long time and can earn the profits. Like wise the MAX31865 evaluation kit helps and acts as the warehouse temperature maintains kit.

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