{"id":2475,"date":"2016-06-30T12:47:17","date_gmt":"2016-06-30T16:47:17","guid":{"rendered":"https:\/\/dyzedesign.com\/?p=2475"},"modified":"2020-10-23T15:30:29","modified_gmt":"2020-10-23T19:30:29","slug":"temperature-sensors-used-3d-printers-part-1","status":"publish","type":"post","link":"https:\/\/dyzedesign.com\/fr\/2016\/06\/temperature-sensors-used-3d-printers-part-1\/","title":{"rendered":"Comparison between temperature sensors used in 3D printers – Part 1"},"content":{"rendered":"

This post\u00a0will help you understand\u00a0the differences\u00a0and\u00a0the operation\u00a0of most common temperature sensors used in 3D Printing.<\/p>\n

Each type of\u00a0sensor has many key performance aspects\u00a0and the goal of this topic is to compare them in\u00a0details.<\/p>\n

Part 1<\/strong>\u00a0will explain the most common sensor types and will take a look at the boards.<\/p>\n

Part 2<\/strong><\/a>\u00a0will go in details about the performance between sensors while keeping in mind the 3D printer application.<\/p>\n

Part 3<\/strong><\/a>\u00a0will provide explanations regarding our choice to go with a thermistor. Finally, some common mistakes are explained regarding temperature sensors.<\/p>\n

Do not hesitate if you have any comments or suggestions that could improve this blog.<\/p>\n

Sensors types used in 3D Printers<\/h1>\n

The most common sensor types are the following:<\/p>\n

Thermistor<\/h3>\n
\"Comparison<\/div>

Glass thermistor<\/p><\/div>\n\n

Thermistor\u00a0are resistor whose\u00a0resistance changes with\u00a0temperature. Most commonly used type in 3D printers is NTC, standing for\u00a0« Negative Temperature Coefficient ». When the temperature increase, the resistance decrease.<\/p>\n

They are made from semiconductors,\u00a0mostly silicon and germanium, and their resistance value can vary by\u00a0many order of magnitude in their temperature range. A 100k NTC thermistor has a resistance of 100k\u2126 (100 000\u2126) at room temperature (20\u00b0C) and drops as low as 100\u2126 at 300\u00b0C.<\/p>\n

RTD<\/h3>\n
\"Comparison<\/div>

PT100 Probe<\/p><\/div>\n\n

RTD are very similar to thermistors in term of operation. Rather than having a semiconductor, these are made from metals, mostly platinum, nickel or\u00a0copper. RTD stands for « Resistance Temperature Detectors ».\u00a0Most commonly used type in 3D printers is PT100. It has a resistance of 100\u2126 at 0\u00b0C.<\/p>\n

With an RTD sensor, the resistance slowly increases with temperature. At 400\u00b0C, a PT100 will reach 250\u2126. The variation is almost linear.<\/p>\n

Thermocouple<\/h3>\n
\"Comparison<\/div>

Thermocouple exposed bead<\/p><\/div>\n\n

Thermocouple operates in a totally different way than the other sensors. They are made from two different metals which generate a very small voltage depending on temperature. The most common type used in 3D printers is K and is made from chromel and alumel.<\/p>\n

The voltage increase from 0mV to 20mV from 0\u00b0C to 500\u00b0C. As with PT100, the variation is almost linear at\u00a041 \u00b5V\/\u00b0C.<\/p>\n

Please note that the picture shows a welded bead sensor which shouldn’t be used inside a 3D printer. The actual\u00a0thermocouple should be inside an electrically insulated housing to prevent any noise or ground effect. A housing can be threaded, cylindrical or flat (crimped).<\/p>\n

3D Printers manufacturer and motherboard sensor\u00a0table<\/h2>\n

Here is a list of 3D printer\u00a0manufacturers with the sensor\u00a0types\u00a0they are using.<\/p>\n

The main driving part inside a printer\u00a0for sensor choice is the motherboard. Each motherboard has unique components which decide what sensor is meant to be used. The most common is the thermistor, which only requires a pull-up resistor to work.<\/p>\n

Both RTD and thermocouple require an IC (Integrated Circuit) built for processing their respective signal. These add-on boards are compatible with most boards via I2C and SPI pins for communication, or analog pins. Some specialized boards, such as the Duet Wifi<\/a>, offer specialized add-on\u00a0board to enable thermocouple and RTD readings.<\/p>\n

\n\n

\"Comparison<\/div>

RAMPS 1.4 - 8 bits - Thermistor<\/p><\/div>\n<\/div><\/div>\n

\"Comparison<\/div>

RUMBA - 8 bits - Thermistor<\/p><\/div>\n<\/div><\/div>\n

\"Comparison<\/div>

AZSMZ - 32 bits - Thermistor<\/p><\/div>\n<\/div><\/div>\n

\n\n\n\n\n\n\n\n\n
<\/th>\nThermistor<\/th>\nRTD<\/th>\nThermocouple<\/th>\n<\/tr>\n<\/thead>\n
Printers<\/strong><\/td>\nPrusa,\u00a0Robo3D,\u00a0BCN3D,\u00a0Kossel,\u00a0Makergear,
\nMendelMax,\u00a0LulzBot,\u00a0Printrbot,\u00a0Mendel90,
\nAnd many more RepRap…<\/td>\n		Ultimaker<\/td>\nMakerBot,\u00a0FlashForge,\u00a0CTC,
\nWanhao Duplicator<\/td>\n<\/tr>\n
\n

Motherboards<\/strong><\/p>\n

8 bits<\/strong><\/p>\n<\/td>\n

RAMPS, Rambo\u00a0RUMBA, Melzi, Sanguinololu, Generation 6, Azteeg X1, Azteeg X3<\/span><\/td>\nUltimaker PCB, Ultimaker Board<\/td>\nMightyBoard, Azteeg X3 Pro,\u00a0Megatronics<\/td>\n<\/tr>\n
\n

Motherboards<\/strong><\/p>\n

32 bits<\/strong><\/p>\n<\/td>\n

Smoothieboard, AZSMZ, R2C2, Generation 7,\u00a0Duet, Replicape<\/span><\/td>\nAlligator Board<\/td>\nRADDS<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n\n

Thermal sensor performance<\/h2>\n

Below is a graphical comparison for certain key aspects of temperature sensing in 3D printers. Please note that these values are\u00a0based on the most common microcontroller configuration used in 3D printing, which is 8 bits microcontroller with 10 bits ADC. Having a\u00a0higher resolution will improve resolution. Most 32 bits microcontroller\u00a0benefit from a 12 bits ADC.<\/p>\n

Better resolution can be obtained with specialized measurement devices, such as MAX31855, AD595, MAX6675 for thermocouple and MAX31865 for RTD, these are considered with both the RTD and thermocouple, as they are required.<\/p>\n

The key performance aspects will be explained and detailed in part 2<\/strong>.<\/p>\n

Thermistor<\/h3>\n