Heated roller

Hi everybody, I am currently starting to work on creating a heated roller and I am quite confused with the electrical part.

The design and concept is quite simple: I want to insert a cartridge heating element inside a metal tube and insert also a thermistor to measure temperature as well as allow me to control the temperature of the roller through a PID controller using the Arduino.

These are the various components:

  • Since (I assume) heating elements consume a lot, I want to connect my Arduino to a socket by using a 12V SMPS I have from another project. That solves supplying power to the Arduino.

  • To lower and lift the roller, I will use a NEMA-17 40mm stepper motor with a 4-pin connector already fitted from a broken printer I have for spare parts.

  • For cooling ahead of the bearing, I will be using the print fan from the broken printer

  • As a thermistor, I will also be reusing this from the printer's hot end (ATC Semitec 104GT-2).

  • Cartridge heater: Here is where I start to doubt. I can only find cartridges with an AC power supply, which for what I understand of their working principle makes sense. However, cartridge heaters for a printers hot end are DC, which confuses me a bit. Also, I cannot reuse the cartridge from the printer because I am looking for bigger dimensions (16mm diameter and 60mm length).

  • Slip ring: I don't want my cables (cartridge and thermistor) to twist and turn with the roller, so after searching I found out about slip rings but, If I understand correctly, slip rings are used for an AC machine. Can they still be used if since both the thermistor and cartridge heater are powered by the Arduino board?

In summary, I am looking for advise regarding the heating element and slip ring. For the heating element, can I use an AC powered element connected to an Arduino? Also about the slip ring, do they only function for AC powered elements? I am looking for something that removes the rotating movement of the roller so the cables dont twist, is there an alternative?

Sorry for the long post, hopefully I was clear on what I am trying to do..! It is (sadly) my first ever project using an arduino and the more I think the more doubts I get.

Thanks in advance!

It might be useful to know the project .
These are all mechanical design issues and only you know the full spec of what you need and are trying to do , and little detail is provided - what size roller, how hot, what rpm etc ....google is a friend here to find what’s available ...

Having said that..
If your roller is mounted from one end only , with the other end open the heater , thermistor etc can be static/fixed and mounted through the other open end so no slip rings etc needed.
Depending on what you are doing there maybe other options , such as externally heating the roller on the underside , IR heating from above and so on.

Slip rings (unbroken) are not appropriate, for example, for DC motors, but should be entirely suitable for what you are doing.
Post a link to a heating element you’ve found. A pure resistive heating element should be insensitive to the difference between AC and DC.
What is going to be in the roller itself? Just the heater and thermistor ? To limit the number of slip rings, the circuit inside the roller should be as autonomous as possible.

Read a thermistor through slip rings? What is the cartridge wattage? You could read the temperature of the roller exterior with an IR thermometer while it rotates at ? RPM and ? temperature.

Thank you for your replies. I have attached some pictures of what I want to do more or less. (the pictures don't show where the thermistor would be connected)

To Hammy, the roller diameter is 30mm, I am limited by the roller bearing I am using which have an outer diameter of 22mm. RPM is really low, around 20 RPM. The maximum temperature I want to reach is 250°C. Also, you mentioned that if the roller is mounted from one end only, the thermistor can be fixed mounted to the open end of the roller, but this end would also be rotating so I would need something to remove that rotation and that is why I considered the slip ring. I have tried google before posting here, but I somehow always end with more questions than answers...!

To 6v6gt, what do you mean "unbroken" slip rings? Also, yes, the roller will only have the heater and thermistor. About the heating element, the link is the following: https://smartstore.naver.com/sunty/products/4521369941?NaPm=ct%3Dkl7oplaw|ci%3D63211d8b42af80dac6e96308e01768484f9257dd|tr%3Dslsl|sn%3D420625|hk%3Db6770ef2763acb18e1f5d3d873c45b9b617baadf . I am in South Korea at so I am greatly limited in my buying options to Korean retailers, as otherwise I would have to pay customs. The cartridge from this website is 220V, 15 mm in diameter and 60 mm length, and has a wattage of 120w.

To JCA34F, is not possible to read a thermistor through slip rings? My confusion comes in that I was under the impression slip rings can be used to simply eliminate the rotating movement. I have thought about the IR thermometer too, but I would like something more precise as the thermistor. Lastly, the roller would rotate slowly, around 20 RPM at a max. temperature of 250°C.

Thank you all!

Screenshot 2021-02-17 214344.png

Screenshot 2021-02-17 214344.png

I would reconsider your method of temperature sensing. A thermistor measures the temperature at a SINGLE POINT, not the temperature of the cylinder. An IR temperature sensor could indicate the temperature of a much larger area.
Paul

Hi Paul, thank you for your recommendation. I am aware, that the thermistor measures only a single point, but it is also easier to control the temperature through the PID controller by using a single point.

Anyway, my doubt is regarding the requirements of a heating element to be used with an Arduino board. Does it need to be DC current? Most of the ones I can find are 220VAC, but I know that 3D printers for example use 12VDC/24VDC connected directly to their Einsy RAMBo board.

ukepa:
Hi Paul, thank you for your recommendation. I am aware, that the thermistor measures only a single point, but it is also easier to control the temperature through the PID controller by using a single point.

Anyway, my doubt is regarding the requirements of a heating element to be used with an Arduino board. Does it need to be DC current? Most of the ones I can find are 220VAC, but I know that 3D printers for example use 12VDC/24VDC connected directly to their Einsy RAMBo board.

Your Arduino has to CONTROL the device that controls the heating power. Whether that is a MOSFET to control DC power or a SSR, solid state relay, to control AC power is all up to you. Both are just as easy as turning a LED on and off.
Paul

How accurately do you need to control temperature? The proper relation of thermistor resistance to temperature is done with the Steinhart-Hart equation, which is quite nonlinear. With a slip ring, you may have a slightly variable electrical path, and using the thermistor could be tricky.

Hi,
Welcome to the forum.

Have you looked at the heated rollers used in laser/zerox photocopying machine and laser printers?
They are called fusers in these machines.

This link might give you some ideas.
https://mindmachine.co.uk/book/print_19_fusers.html

Tom.. :slight_smile:

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