unknown digital infrared thermometer chips - Page 1
Forum section: electronics / projects

author: uwezi
author_rank: Unknown
timestamp: March 22, 2015, 10:52:36 pm
content: Hello!I recently got some unmarked TO-39 chips as a bonus during an eBay-transaction. These look exactly like Melexis' thermopile sensors. They come with two types of aluminum apertures exactly like the MLX90614.I was able to communicate with the chips using I2C, the pinout is the exact same as the MLX90614, however, the data sent back does not make sense. Especially there is no difference between the data sent back as an answer ot the EEPROM read request and RAM read request.Has anyone seen any chips like these - unmarked thermopile sensors - and knows more about them?I will continue to try to reverse engineer them, but any help is appreciatedUwe.

author: kilobyte
author_rank: Regular Contributor
timestamp: March 23, 2015, 09:06:40 pm
content: Hi,I got also some of these part? Did you orded some LM399?I've opened one up and took some macro fotosOn the sensor itself i can see something that could match the mlx81101 sensor element

author: uwezi
author_rank: Unknown
timestamp: March 25, 2015, 03:09:18 pm
content: Quote from: kilobyte on March 23, 2015, 09:06:40 pmYes, I did, how do you knowThanks for the nice picture - I also had planned to open one...In the meantime I have found out what they are and managed successfully to communicate with them.These are indeed MLX90614 - most probably the 3.3V version. All of the ones I have tested so far reply when queried by I2C, but there is something weird with the temperature response.According to the datasheet there are 3 fields with temperature data: ambient temperature and object temperature for the two possible thermopile sensors inside. If only one thermopile is mounted, you would only expect one of the 2 values to be reasonable. And from your photo it is obvious that at least that one only had one thermopile mounted.The two chips with the long black aperture which I got give very reasonable values for the object temperature of sensor 1. But the chips with the short aperture only read back the ambient temperature in all 3 fields. This temperature however, appears to be accurate and correctly increases when you warm the case with your finger.Additionally you can read out the thermopile raw data in two other memory locations - and these show exactly the same behavior for the chips with long or short aperture - meaning that the thermopile inside works correctly. Something must be misconfigured - probably in the filter settings (a combination of two digital filters, IIR and FIR).http://www.melexis.com/Asset/IR-sensor-thermometer-MLX90614-Datasheet-old-647-DownloadLink-5152.aspx

author: uwezi
author_rank: Unknown
timestamp: March 25, 2015, 03:19:15 pm
content: Quote from: kilobyte on March 23, 2015, 09:06:40 pmI originally excluded the MLX90616 (which contains the MLX81101 element) because its datasheet does not show the availability of the different apertures......and looking at the datasheet, the MLX90616 only states temperature data for RAM address 0x07, but I read temperature data back even from 0x08.I just found another link on the internet stating that even the -14 contains the same sensor elementhttp://www.edn.com/Pdf/ViewPdf?contentItemId=4407716

author: dan230793
author_rank: Newbie
timestamp: March 03, 2016, 05:54:44 pm
content: Hi,I´m using MLX90616 for a project but I have a problem accesing to the registers of Ta and To. With the code I use, the ambient and object temperature is the same. I use PIC18F2550 and Proton to program the microcontroller. Can you help me with this?

author: jan.didden
author_rank: Newbie
timestamp: July 16, 2016, 10:28:54 am
content: Could it be that the ambient and device temp are the same because of the large aperture, that you are in fact measuring the ambient temp?Jan Didden