In this article I will explain the 3 types of temperature sensor In 3D Printing that are most commonly used for Heating Block and Heated Beds.
To be able to detect the temperature of the Heating Block and Heated Bed, an extreme Temperature Sensor In 3D Printing is needed.
There are many types of temperature sensors, such as:
- Thermistor (NTC dan PTC)
- RTD Sensor (PT100 dan PT1000)
- Thermocouple (k type thermocouple)
However, especially for 3D printer machines, they must require sensors that are able to withstand and read above > 100°C, even some printers must have sensors that are able to read temperatures up to 500°C more.
From these conditions, the most commonly used temperature sensors for 3D printers are Thermistor, RTD and Thermocouple.
Thermistor vs RTD vs Thermocouple
Thermistor is stands for Thermal Resistor, which is a resistor whose resistance will change in proportion to changes in temperature.
a. Types of thermistors based on how they work
Generally, thermistors are made of silicon and germanium, and their resistance values can vary in proportion to changes in the temperature range.
Therefore, based on the workings of the constituent materials, there are two types of thermistors, NTC and PTC. The differences are:
- The resistance on the NTC (Negative Temperature Coefficient) thermistor will decrease if the temperature rises.
- The resistance on the PTC (Positive Temperature Coefficient) thermistor will increase if the temperature rises.
For 3D printers, the most thermistor type commonly used is NTC and is well programmed in Marlin Firmware.
A 100k NTC thermistor has a resistance of 100kΩ (100,000Ω) at room temperature (20 °C) and drops as low as 100Ω at 300 °C. This is a very frequently used thermistor value for 3D printers.
b. Types of Thermistors Based on Packaging
Generally, there are 3 types of thermistors packaging that are often used, glass, stainless steel, and DO-35.
However, the most commonly used thermistor forms are Glass and Stainless Steel, because their sizes are suitable for placing in heating blocks and heated beds.
Look at the following picture, stainless steel (left) and glass (right):
c. MainBoard Controller Example Using Thermistor
There are many manufacturers that make 3D machines, but it will be different controller board used, there are 8-bit and 32-bit.
Some 3D Printer machines that use thermistors are:
Some mainboards that use thermistors are:
- RAMPS, Rambo RUMBA, Melzi, Sanguinololu, Generation 6, Azteeg X1, Azteeg X3 (8-bit)
- Smoothieboard, AZSMZ, R2C2, Generation 7, Duet, Replicape (32-bit)
RTD (Resistance Temperature Detector) is a temperature sensor which is basically the same as a PTC thermistor.
The resistance value will increase as the temperature increases. but what is the difference with PTC thermistor?
Here are the basic differences of them:
- RTDs are good for temperatures above 300°C, while thermistors are good for temperatures below 300°C.
- The maximum temperature of an RTD can be up to +850°C while thermistors are generally only +350°C, although some are capable of reading up to +600°C.
- The temperature ratio curve for an RTD is relatively linear as it has standard curves and tolerances, while the curve of the thermistor varies depending on the manufacturer.
- RTD response time speed is slower than thermistor.
- RTD temperature readings are not very accurate when compared to the thermistor.
- RTDs can have 2-wire single, 3-wire single, 4-wire single and 3-wire dual, while thermistors generally have only 2-wire singles.
- RTDs are more expensive than thermistors.
For the physical form of the RTD, some of them are similar to the Stainles Steel thermistor. You can see the shape as in the following image:
Based on the packaging, in generally do not use stainless steel but Platinum, Copper and Nickel.
The most commonly used RTD for 3D printers is the PT100, where this sensor has a resistance of 100Ω at 0°C.
With an RTD sensor, the resistance slowly increases with temperature. At 400 °C, PT100 will reach 250Ω.
The variation is almost linear. In addition, there is also the PT1000 type which has a resistance of 1000Ω at 0 °C.
PT1000 is preferred to be used for measuring low temperatures because it has a higher accuracy compared to PT100.
One of the manufacturers that use RTD for their main board is Ultimaker (Ultimaker PCB, Ultimaker Board). In addition, the main board that uses RTD is the Alligator Board 32-bit MCU.
A thermocouple is a temperature sensor capable of reading -100° C to +1200° C.
The workings of a thermocouple sensor are different from the two sensors above.
The thermistor and RTD will change their resistance as the temperature changes, while the thermocouple will produce voltage in the two metals (legs) when there is temperature.
The higher the perceived temperature, the higher the voltage generated. But, this electric voltage is very small. So, it is necessary to add components such as ADC to use it.
The most common type used in 3D printers is the K Type Thermocouple and is generally made of chromel and alumel.
Voltage increases from 0mV to 20mV from 0°C to 500°C. Like the PT100, the variation is nearly linear at 41 V/°C.
The thermocouple must be in an electrically insulated enclosure to prevent noise or ground effects. the wrapper can be threaded, cylindrical or flat (crimped).
Some of the physical forms are similar to the RTD, but have been packaged as well as possible. You can see some forms of RTD in the following picture:
Hopefully this article on Temperature Sensor 3D Printing Machines can provide images for you to be able to custom design the board and choose the right sensor.