Thermistors are cost-effective thermal resistors that are commonly used for commercial and industrial purposes. These semiconductors show exact changes in resistance values in object or body temperatures. They are passive devices that do not pass or carry electricity; instead, they detect temperature variations. However, they are more effective resistors than conducting products but lesser than other insulating things.
Thermistor material is a very important factor that determines its effectiveness and accuracy. For understanding 3d printer thermistors, you need first to understand the basic mechanism of their working, configuration, and properties. 3d printer thermistor comes in different shapes, sizes, and textures. This article covers all major segments that will help you find a perfect thermistor that will suit your 3d printer.
History Of Thermistor
Michael Faraday had studied silver sulfide properties and semiconductor nature and first proposed the concept of the thermistor in 1833. Silver sulfide’s resistance decreases when you will increase the temperature. It was Samuel Ruben who used this information and invented the modern thermistor.
Since the 1930s, thermistor technology has been evolving with upgrading features that are helping for better production. The Steinhart-Hart equation is used for converting thermistor resistance into temperatures accurately. It was developed by John S. Steinhart and Stanley R. Hart and published in “Calibration curves for thermistors” in 1968.
Function Of 3d Printer Thermistor
Thermistors play a very important role in 3d printer machines as they show exact heat heating temperatures for nozzles and printing beds. It is very important to know the heating temperatures for making perfect 3d objects.
Otherwise, the materials or filaments might succumb to excess heat and deform it. By using 3d printer thermistors, you can adjust heating and know the exact heating levels. Apart from thermistors, there are other such devices like RTDs and thermocouples that you can use for the same purpose.
Types Of Thermistor
You will find two thermistors-negative temperature coefficients (NTC) and a positive temperature coefficient (PTC) in different applications. It depends upon the machines, their functions, and processing because both kinds work differently.
Negative Temperature Coefficient Thermistor
Negative temperature coefficient (NTC) machines’ resistance decreases when you will increase the temperature. The 100k NTC thermistor has a resistance of 100kΩ at room temperature and drops as low as 100Ω at 300°C. They come in various shapes like a bead, rod, disc, or chip made from sintered metal oxides. They are non-linear and might get affected by the self-heating phenomenon.
NTC thermistors come with or without a coating of tinned copper and different configurations. NTC thermistors come with or without a layer of tinned copper and other designs. In such devices, electricity passes through it, and the thermistor absorbs heat that increases its temperature. They respond very quickly.
Positive Temperature Coefficient Thermistor
Positive temperature coefficient (PTC) machines’ resistance increases when you will increase the temperature. Thermistors for PTC devices are made from polycrystalline ceramic (barium titanate) to protect them from excessive temperature during sudden resistance increments.
It offers less operating cost, is reliable and protective. However, the resistance value might get affected due to the self-heat of the device. Ceramic switching PTC thermistors produce a highly non-linear resistance curve on the screen.
Silicon PTC Thermistor
Silicon PTC thermistors also have positive temperature coefficient resistance and are linear devices. It works well under 150 °C temperature. If it exceeds, you need to switch to NTC devices. They are stable, durable, and come in multiple configurations.
Polymeric Thermistor
The Polymeric thermistor is also called a resettable fuse. It is a PTC thermistor and has a non-linear PTC effect. Its temperature reading is directly affected by changes in room temperature. Under normal circumstances, it will show a lesser resistance value and no impact on the circuit performance.
A faulty circuit system will deliver a higher resistance value. They are a good option to overcome overcurrent issues. Moreover, they are resettable, compact-sized, low-resistant, and come in multiple configurations.
Thermistor In 3d Printers
A 3d printer has more than one thermistor because of several factors. Some important parts like the printer’s nozzle and print-bed consist of thermistors to show their heating amount. You can find them inside the machine console wrapped in silicone filament.
The wires connected to thermistors measure temperature. All these wires are connected to the main controller board, which handles all heating processes. The controller board generates calibration data to calculate electrical resistance and heating temperatures.
How To Check 3d Printer Thermistor’s Resistance
A 3d printer thermistor has a resistance of 100k at room temperature. You cannot measure resistance directly by producing current flow in the thermistor and calculating the opposition through a multimeter device. To get a proper resistance reading, we suggest you rely on the room temperature data.
- Take a multimeter and set its range to the given resistance limit of your 3d printer thermistor at room temperature, usually 25℃.
- You can check the resistance value by attaching a multimeter.
Errors In Thermistor Calculations
Sometimes thermistors also interpret wrong calculations and give false data because of their malfunctioning issues caused by various factors. You need to keep an eye and look for these issues to avoid inaccurate information. The reasons can vary from printer to printer, but here are some frequently occurring causes-
Faulty Sensors
One of the major reasons for thermistor miscalculation is faulty wires and sensors that fetch the wrong temperature to the printer. It results in a constant heat supply and melting filaments. The machine and work area can also catch fire if you miss this error. Nowadays, it comes with firmware to avoid such mishaps.
Different Temperature Issues
Different materials have variations in extrusion temperatures and require heat accordingly. But thermistors fetch thermal data to a certain temperature degree. If the printer or the material needs more than the recommended print temperatures, the thermistor will not bring it and produce the wrong information.
Prolonged Exposure To High Temperatures
If the thermistor is exposed to higher temperatures for longer durations and used over the years, it might get wary and give incorrect resistance data. You might get an increased resistance value even at a lower temperature.
Wrong Calibration Data And Circuit Issues
If the 3d printer has different or wrong calibration data, thermistors will not fetch the right resistance information. Similarly, if the circuits of the print bed or the hot-end of the 3d printer have faulty wire connections with sensors, it will also affect the reading.
Calibration Of 3d Printer Thermistor
The term ‘calibration’ means comparison between a known measurement and the measurement using your instrument. Usually, different thermistors have varied resistance temperatures and have different calibrations.
For example, thermistor data information is more accurate at lower temperatures than high temperatures. But nowadays, these calibration data are already given by manufacturers for better performance.
However, you can also change the calibration of your 3d printer thermistor according to your preferences if you know the basic configuration. Most 3D printer thermistors have a resistance equal to 100 kΩ at room temperature and have a calibration data list under varied temperatures. You have to feed this data to the printer’s firmware and connect it to the main circuit board.
How To Replace Thermistor To 3d Printer
Thermistors are found in very deep parts of the printers, so removing or changing the defective wires is tough. Moreover, they tend to break or are prone to malfunctions.
Thermistors are important in calculating heat and act as resistors; you need to keep them updated and replace defective ones continuously. Two major sections where you will find a thermistor in a 3d printer are Hot End and Printing Bed. You need to follow some basic precautionary measures to remove and replace them as your own.
Hot End
There are some variations in the procedure in different 3d printers but mostly follow the same pattern. For replacing a new thermistor, you need to follow the below instructions.
- First, you need to check the heat temperature data of your 3d printer to get a suitable thermistor.
- Using the printer’s micro-controller system, remove the correct old thermistor wire using a tool like a tweezer.
- Now carefully place the new thermistor in that place and screw it. Do not excess tight or loose screws to protect it from damage.
- Cover it back by using Kapton tape so that these wires do not jumble up.
- Now you can cover the printer’s panels and start the hot end to check the thermistor.
Print Bed
Like a hot end, the print bed also has some variations in the procedure in different 3d printers but mostly follows the same pattern. For replacing a new thermistor in a print bed, you need to follow the below instructions.
- To remove the defective thermistor wire, you first need to open the print bed panel by disconnecting it from the Power Supply Unit. Then remove all the attached screws.
- Remove the tape or insulation covering of the thermistor carefully. Cut the wires of the old thermistor from the device. Then lift it.
- Now, put the new thermistor inside and attach it to the sensor’s wires using Kapton tape.
- Attach the print bed with the 3d printer after replacing the thermistor by screwing all nuts.
Steinhart-Hart Equation In Thermistor
The Steinhart-Hart equation is used for converting thermistor resistance into temperatures accurately. Earlier, it was done manually, but now you can easily calculate through computer software. This equation calculates the real resistance value of the thermistor. It converts it into a temperature reading with utmost accuracy, where if the temperature is lower, the resistance value will be more accurate.
The Steinhart-Hart equation= 1/T = A + B(lnR) + C(lnR)3, where T stands for temperature in Kelvins (K, Kelvin = Celsius + 273.15) and R stands for resistance at T in Ohms (Ω). A, B, C are the Steinhart-Hart coefficients that vary depending on the type of thermistor used and the range of temperature being detected.
Different-Shaped Thermistors
Thermistors are available in different shapes and sizes, depending upon their application. If the application needs surface mounting, you can get the chip and rod-shaped thermistors. For embedding purposes, bead-shaped thermistors are available. How the thermistors will be attached to the applications like resin, glass, or mounting also defines their shapes.
Different Configurations Of Thermistor
Though several kinds of configuration for thermistors are available, I will talk about the most frequently used configurations.
Hermetically Sealed Flexible Thermistor (HSTH Series)
Hermetically sealed flexible thermistors (HSTH series) have packaging of plastic polymer to protect from corrosion or moisture. You can use such thermistors to measure liquid temperatures. It is used for oil and chemical industries.
Bolt-on/Washer Type Thermistor
Such thermistors come in standard sizes and can fit well into applications with holes. They quickly respond to temperature variations and give accurate data. You will find these thermistors in household applications, pipes, and water tanks.
Surface-Mount Style Thermistor
Surface-mount style thermistors are easy to attach to flat as well as curved surfaces. They have special coatings of adhesives as well. You can remove and use them again as per the need. They are popularly used for commercial and industrial applications.
Function Of Thermistor In Controlled System
Thermistor sends the resistance data to the device’s control panel monitor, instructing the device to either switch on or off and control the voltage. The device’s control panel needs voltage to read the thermistor’s resistance data.
You should place the thermistor near the device to check temperatures for reliable information. Thermistors are non-linear, meaning the temperature to resistance values plot on a graph as a curve rather than a straight line.
Ideal Temperature-Ranges Of A Thermistor
Thermistors do not give accurate readings if the temperature is very high or low. So, we need to know the ideal temperatures for it. Usually, it works best for measuring a single temperature at room temperature. It works well between -55°C and +114°C as per the calibration data.
Thermistors also vary their resistance due to their configuration and material sensitivity. Voltage is a crucial detriment for the effectiveness of the thermistor. You can use the Steinhart-Hart equation to convert thermistor resistance to temperature.
Depending on the base resistance, it gives accuracy within a limited temperature range of about 50ºC around the given temperature. You will need lower resistance thermistors ranging from 2252 to 10,000Ω for low-temperature applications.
Similarly, for high-temperature applications, use higher resistance thermistors ranging above 10,000Ω. Different coatings are done on the thermistors to protect them from excess heat, humidity, corrosion, and malfunctioning. Thermistors having epoxy coatings are used for low temperatures, whereas thermistors with glass coating are preferred for higher temperatures.
Advantages Of Thermistor
If you are thinking of switching to other sensors, you should know these thermistors’ advantages.
- Thermistors are more durable than other thermal resistors available in the market.
- It is sensitive and will fetch you accurate data.
- It comes in small sizes. You can attach it easily, and it fits well.
- Thermistors are available at cheaper rates.
Things To Consider While Buying New Thermistor
If you are planning to buy a new thermistor or planning to replace the defective one, there should be certain things that you need to consider. Here is your checklist-
- Go for thermistors that have better resistance capacity at different temperature ranges in the 3d printer. We suggest you go for thermistors having a resistance of at least 100kΩ.
- Choose those thermistors that can check different temperature ranges in the 3d printer so that you get accurate data and not faulty calculations.
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A picture by Goncharenko Vladimir, Shutterstock, Copyright-2021 - Thermistors should be made of proper insulations and sensitive materials for stable conditions. You can go for aluminum thermistors as well.
- Always rely on branded thermistors or buy the same brand and configuration. Manufacturers provide their configuration and capabilities. Look for your requirements because, in some control panels, thermistors behave differently.
Different Sensors Used 3d Printer
RTD
RTD stands for Resistance Temperature Detectors and is used for resistance calculations, same as thermistors. These detectors are made from metals like copper, platinum, and nickel.
Some 3d printers do not have thermistors but RTD for the same purpose. RTD has a resistance of 100Ω at 0°C, and sensors show linear variation. For example, in RTD, the resistance curve will increase when you increase the temperature of 3d printer.
Thermocouple
The thermocouple is an electrical device that forms an electrical junction due to two different metal conductors and produces voltages according to varying temperatures.
It works differently and is mostly found in 3d printers. It is made of chrome and alumni and can be fixed in different positions. It is placed inside the insulating tube to avoid jumbling with other wires or noise.
Different Applications For Thermistors
Apart from 3d printers, thermistors are also used for thermal resistance data to measure the temperature of surfaces, liquids, and gasses as well in other applications like circuit components, optical blocks for measuring oil and coolant temperatures in vehicles, ovens, refrigerators, laser stabilization detectors, and digital thermometers.
They are also used in food and beverage industries, laboratories, instrumentation, fire alarms, aerospace, and outdoor biological applications. Thermistors are important for the safety of electrical circuits that might get affected due to high temperatures.
3d Printer Thermistors Available In The Market
Here is a listicle of 3d printer thermistors available online where you can find one of the best thermistors for your machine in budget.
1. uxcell NTC Thermistors Resistors MF58 3950B 50K Ohm Glass Sealed Temperature Sensors
This small 3d printer thermistor is available on Amazon. It comes in glass-sealed packaging with a firm structure. It is compatible with various applications, is light-weighted, and ensures precision in resistance calculations.
2. ToToToT MF52-103-3435B Thermistors Negative Temperature Coefficient Black Head
ToToToT MF52-103-3435B Thermistors Negative Temperature Coefficient Black Head has an epoxy coating on coaxial lead. They have wide as well as high resistance and accurate B value. Their reflection speed is fast and precise while testing. You can go for them for longer and consistent operations.
3. Genuine E3D Hotend Thermistor Cartridge Replacement
Genuine E3D Hotend Thermistor is a custom-made thermistor that can be directly replaced in E3D hot end. It comes with a wire extension. Click here for more details.
4. Comgrow 3D Printer NTC Thermistor Temp Sensor 100K for Ender 3 / Ender 3 Pro/Ender 5 / CR-10 / CR-10S
Comgrow 3D Printer NTC Thermistor is compatible with print-bed for extrusion in Reprap Prusa I3 3D Printers. It has a wire length of approx 1m and two female pin connectors. It has high insulating sensors of 100KΩ that give accuracy of ± 1%. Usually, these thermistors are in small-sized glass beads. You can find it here.
5. Gikfun NTC MF58 3950 B 10K ohm 5% Thermistor Temperature Sensor for Arduino EK2157
Gikfun NTC MF58 3950 B 10K ohm 5% Thermistor Temperature Sensor for Arduino EK2157 comes in glass sealed packaging with a firm structure. It is compatible with various applications, is light-weighted, and ensures precision in resistance calculations. Click here for more details.
Summary
Thermistors are passive devices that do not pass or carry electricity; instead, they detect temperature variations. However, they are more effective resistors than conducting products but lesser than other insulating things. The Steinhart-Hart equation is used for converting thermistor resistance into temperatures accurately.
Thermistors are available in different shapes and sizes, depending upon their application. They play a very important role in 3d printer machines as they show exact heating temperatures for extruders, nozzles, and printing beds.
The controller board generates calibration data to calculate electrical resistance and heating temperatures. We hope that you find this article helpful and it adds value to your prior knowledge.
