By: Robert O

Robert O — Wed, 06 Mar 2024 01:36:03 +0000

Really helped me with my project. Thank you

By: Oleg Kutkov

Oleg Kutkov — Mon, 06 Feb 2023 20:00:13 +0000

In reply to Team. The whole article is about using MLX90614 with Raspberry Pi

By: Team

Team — Mon, 06 Feb 2023 19:49:33 +0000

Is the MLX90614 compatible with the Raspberry Pi?

By: Oleg Kutkov

Oleg Kutkov — Sat, 16 Jul 2022 23:53:19 +0000

In reply to Stephen Petersen. The sensor is mounted on the box with Raspberry PI and other electronics inside. It just tightly sits in a hole and is secured with sealant.

By: Stephen Petersen

Stephen Petersen — Sat, 16 Jul 2022 23:47:46 +0000

In reply to Oleg Kutkov. Thanks for the very quick response. Are you using a cable gland or something similar?

By: Oleg Kutkov

Oleg Kutkov — Sat, 16 Jul 2022 23:46:21 +0000

In reply to Stephen Petersen.

Hello. That’s correct.
I’m using my MLX sensor outdoor without any cover on the top. It’s waterproof. Sure, bottom contacts are hidden inside a box, but the top panel window is exposed to the open sky.

By: Stephen Petersen

Stephen Petersen — Sat, 16 Jul 2022 23:42:09 +0000

I read somewhere that for the sensor to be accurate, you have to expose it to the sky without anything like a plastic dome to cover it. If that is correct, how do you do that? TIA!!

By: Oleg Kutkov

Oleg Kutkov — Thu, 09 Jun 2022 19:25:23 +0000

In reply to farm2440. Thank you for your comment. Fixed!

By: farm2440

farm2440 — Thu, 09 Jun 2022 19:16:46 +0000

VSS – power supply (3.3 or 5 volts). : Watch out!!! This is wrong! VSS is ground and VDD is positive power supply.

By: Kulwant Singh

Kulwant Singh — Sat, 04 Dec 2021 00:29:08 +0000

Hi Oleg!
I’m hoping you are still reading this and can help me with an issue I’m having with setting emissivity on 90614DCC sensor.

I’m following the steps in MLX90614-Changing-Emissivity-Unlocking-Key-Application-Note-Melexis section 6.2. I’m able to read and write to the EEPROM locations as specified except for the very first step which is to “Enter EEPROM address 0x0F unlock key”.
I have tried reading from 0x60 (as listed in opcode column) but this address doesn’t exist so there’s an error. Also tried writing 0x0F to 0x60 but that didn’t work either.
If I skip this step and follow the rest of the steps as following, new values written are not saved. I read old values back:
-Write 0x0000 to 0x24 (Erase emissivity)
– write new emissivity to 0x24
– read back emissivity (Reads old value, not new)
– write 0x0000 to 0x2F (Erase )
– write new value to 0x2F
– read 0x2F (returns old value, not new)

I’m wondering if there is an error in the datasheet section 6.2.1 “Enter EEPROM address 0x0F unlock key” or whether I am doing something wrong.

Any ideas to try out are appreciated.

Code:
from time import sleep
import smbus

class MLX90614():

# RAM offsets with 16-bit data, MSB first # Raw data IR channel 1 MLX90614_RAWIR1 = 0x04 # Raw data IR channel 2 MLX90614_RAWIR2 = 0x05 # Ambient temperature MLX90614_TA = 0x06 # Object 1 temperature MLX90614_TOBJ1 = 0x07 # Object 2 temperature MLX90614_TOBJ2 = 0x08


# EEPROM offsets with 16-bit data, MSB first

# Object temperature max register

MLX90614_TOMAX = 0x20

# Object temperature min register

MLX90614_TOMIN = 0x21

# PWM configuration register

MLX90614_PWMCTRL = 0x22

# Ambient temperature register

MLX90614_TARANGE = 0x23

# Emissivity correction register

MLX90614_EMISS = 0x24

# Configuration register

MLX90614_CONFIG = 0x25

# Slave address register

MLX90614_ADDR = 0x2E

#EEPROM Unlock key

MLX90614_UNLOCK_KEY = 0x2F

# 1 ID register (read-only)

MLX90614_ID1 = 0x3C

# 2 ID register (read-only)

MLX90614_ID2 = 0x3D

# 3 ID register (read-only)

MLX90614_ID3 = 0x3E

# 4 ID register (read-only)

MLX90614_ID4 = 0x3F
comm_retries = 5

comm_sleep_amount = 0.1
def __init__(self, bus_num = 1, address=0x5A):

    self.address = address

    self.bus = smbus.SMBus(bus=bus_num)
def read_reg(self, reg_addr):

    err = None

    for i in range(self.comm_retries):

        try:

            return self.bus.read_word_data(self.address, reg_addr)

        except IOError as e:

            err = e

            # "Rate limiting" - sleeping to prevent problems with sensor

            # when requesting data too quickly

            sleep(self.comm_sleep_amount)

    # By this time, we made a couple requests and the sensor didn't respond

    # (judging by the fact we haven't returned from this function yet)

    # So let's just re-raise the last IOError we got

    raise err
def write_reg(self, reg_addr, data):

    err = None

    for i in range(self.comm_retries):

        try:

            return self.bus.write_word_data(self.address, reg_addr, data)

        except IOError as e:

            err = e

            # "Rate limiting" - sleeping to prevent problems with sensor

            # when requesting data too quickly

            sleep(self.comm_sleep_amount)

    # By this time, we made a couple requests and the sensor didn't respond

    # (judging by the fact we haven't returned from this function yet)

    # So let's just re-raise the last IOError we got

    raise err
def read_temp(self, reg):

    data = self.read_reg(reg)

    temp = (data * 0.02) - 273.15

    return temp
def get_ambient(self):

    return self.read_temp(self.MLX90614_TA)
def get_object_1(self):

    return self.read_temp(self.MLX90614_TOBJ1)
def get_object_2(self):

    return self.read_temp(self.MLX90614_TOBJ2)
def get_emmissivity(self):

    return self.read_reg(self.MLX90614_EMISS)
def get_unlock0F(self):

    return self.read_reg(self.MLX90614_UNLOCK_KEY)
def set_unlock0F(self, data):

    return self.write_reg(self.MLX90614_UNLOCK_KEY, data)

def set_emmissivity(self, data): #self.read_reg(self.MLX90614_UNLOCK_KEY) self.write_reg(self.MLX90614_EMISS, 0x0000) return self.write_reg(self.MLX90614_EMISS, data)

if name == “main“:

#bus = smbus.SMBus() IRTemp = MLX90614(1)


print("TO Max: ", IRTemp.read_temp(IRTemp.MLX90614_TOMAX))

print("TO Min: ", IRTemp.read_temp(IRTemp.MLX90614_TOMIN))

print("Ambient Temperature (deg. C): ", IRTemp.get_ambient())

print("Object Temperature (deg. C): ", IRTemp.get_object_1())
emissOld = IRTemp.get_emmissivity()

print("Old Emmissivity: ", emissOld)

print("unlock 0x60 read: ", IRTemp.read_reg(0x0F))

print(IRTemp.write_reg(0x60, 0x0F))

unlockOld = IRTemp.get_unlock0F()

print("unlock Old: ", unlockOld)

#calculate emmissivity

#Treal = float(input("Real object Temp:"))

#Areal = float(input("Real ambient Temp:"))

Treal = 25.4

Areal = 28.9

Tsens = IRTemp.get_object_1()

Asens = IRTemp.get_ambient()
emiss = ((Tsens+273.15)**4 - (Asens+273.15)**4)/((Treal+273.15)**4 - (Areal+273.15)**4)

emissReg = round((2**16)*emiss - 1)

emisshex = hex(emissReg)
print(f"calculated emmiss:{emiss}, reg value: {emissReg}, hex:{emisshex}")

unlockNew = round(emissOld*unlockOld/emissReg)
print("New Emmissivity: ", emissReg)

print("New Unlock: ", unlockNew)

print("unlock 0x60 read: ", IRTemp.read_reg(0x0F))

IRTemp.set_emmissivity(emissReg) print("Read Emmissivity: ", IRTemp.get_emmissivity()) IRTemp.set_unlock0F(0x0000) IRTemp.set_unlock0F(unlockNew) print("Read Unlock: ", IRTemp.get_unlock0F())

Comments on: Connecting MLX90614 infrared thermometer to the Raspberry PI

By: Robert O

By: Oleg Kutkov

By: Team

By: Oleg Kutkov

By: Stephen Petersen

By: Oleg Kutkov

By: Stephen Petersen

By: Oleg Kutkov

By: farm2440

By: Kulwant Singh