Thermocoupler Question (v1 vs v2)

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haylcron
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Thermocoupler Question (v1 vs v2)

Postby haylcron » Sun Mar 05, 2017 6:55 am

Per my other post, I have a feeling I'll be buying a thermocoupler soon. The page says to get the correct version for my printer, but I'm not sure which that is - let me explain.

I have a v1 printer from the kickstarter. I replaced the hotend with the v2 when it was released but I did not change out the thermocoupler. If I need to replace mine, do I order a v1 or a v2? Feels like a silly question to ask, but I just want to be 100% sure.

Jetguy
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Re: Thermocoupler Question (v1 vs v2)

Postby Jetguy » Sun Mar 05, 2017 7:16 am

A thermocouple is a thermocouple. Yes, the new style is all about wiring protection and installation, but the entire point of using a thermocouple is they are accurate to within 3C of any 2 of the same type (K type refers to the type of metal wire used Alumel and Chromel is K).

If there is a claimed difference, that is a problem and is bogus.

Now yes, I understand why Raise 3D would like the new version, it's much harder to damage during install and less user complaints and replacements. But again, a thermocouple in and of itself is the one of the simplest sensors known to human kind. It's 2 specific metal wires, welded together at the sensing end to form a junction. The details about the ones we use is that there is a hollow stainless tube, and the thermocouple junction is mounted inside using a heat conductive but electrically insulating adhesive so that the thermocouple can measure the heat but not short out to the heater block. Why is that electrical insulation so important? Because the junction generates microvolts signal (tiny fractions of a volt). This is why a special instrument amplifier is used (AKA thermocouple amp) to read that microvolt differential signal between the 2 wires- and yet NOT pick up or amplify the typical RFI/EMI common mode noise picked up by everything electrical surrounding the thermocouple wires and junction.

So what the difference in again, is really all about the total package surrounding the actual thermocouple.
Both the OLD and NEW are the same electrically. What is different is how the wires exit the tube that slides into the heater block, and makes that 90 bend upwards to go through the central block. The early ones used fiberglass braided insulation on the wire (technically, the new ones still do- just you cannot see it) and then heatshrink on the end of the tube and up the wires all the way up to the screw terminals at the head breakout. The new versions have a spring (mechanically there to provide strain relief and limit bend radius) and there is braided metal wire shielding on the new ones.

I have 3 Raise 3D printers, N1, N2, and now brand new N2Plus.
Only the N2plus has the new version of thermocouple (the big spring style with the shielded wire). All are running V2 hotends and the older 2 machines have the original as shipped thermocouples. All are within 3 degrees C of each other, actually closer to within 1 C as measured with an external thermocouple contact probe and external meter.

haylcron
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Re: Thermocoupler Question (v1 vs v2)

Postby haylcron » Sun Mar 05, 2017 5:01 pm

Well, that answered my question AND educated me on the principles of a thermocouple. Thanks for the thorough reply!

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Vicky@Raise3D
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Re: Thermocoupler Question (v1 vs v2)

Postby Vicky@Raise3D » Mon Mar 20, 2017 11:46 am

haylcron wrote:Per my other post, I have a feeling I'll be buying a thermocoupler soon. The page says to get the correct version for my printer, but I'm not sure which that is - let me explain.

I have a v1 printer from the kickstarter. I replaced the hotend with the v2 when it was released but I did not change out the thermocoupler. If I need to replace mine, do I order a v1 or a v2? Feels like a silly question to ask, but I just want to be 100% sure.


If you were using the V1 thermocouples on your printer and want to replace to be V2, please leave message when you carry out the purchase that yours is V1. We recommend to add a 224 monolithic capacitor when using V2 thermcouple on V1 extruder board. The temperature will be more stable.

haylcron
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Re: Thermocoupler Question (v1 vs v2)

Postby haylcron » Sat Apr 01, 2017 7:17 pm

Vicky@Raise3D wrote:
haylcron wrote:Per my other post, I have a feeling I'll be buying a thermocoupler soon. The page says to get the correct version for my printer, but I'm not sure which that is - let me explain.

I have a v1 printer from the kickstarter. I replaced the hotend with the v2 when it was released but I did not change out the thermocoupler. If I need to replace mine, do I order a v1 or a v2? Feels like a silly question to ask, but I just want to be 100% sure.


If you were using the V1 thermocouples on your printer and want to replace to be V2, please leave message when you carry out the purchase that yours is V1. We recommend to add a 224 monolithic capacitor when using V2 thermcouple on V1 extruder board. The temperature will be more stable.


Unfortunately, I've already received the new parts and installed them. I noticed the temp is not stable during a test print. How do I add a 224 monolithic capacitor when I get one?

Also, can you link me to an example capacitor to use? There appear to be lots of options and I don't want to mess up my printer.

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walshlg
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Re: Thermocoupler Question (v1 vs v2)

Postby walshlg » Mon Apr 03, 2017 1:54 am

Shoot I didn't do that. I assume you mean 224 pF ceramics?

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Vicky@Raise3D
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Re: Thermocoupler Question (v1 vs v2)

Postby Vicky@Raise3D » Wed Apr 05, 2017 1:49 am

I searched on Amazon, found two similar like ours.

https://www.amazon.com/Electronics-Salo ... 20NF%2963V
https://www.amazon.com/Tian-capacitor-2 ... 20NF%2963V

My search condition are: 224M/63V 0.22UF(220NF)63V.

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walshlg
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Re: Thermocoupler Question (v1 vs v2)

Postby walshlg » Wed Apr 05, 2017 4:41 pm

Ahh, thanks for clarifying, 220 nF, not pF - i'm off by 1000x!

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walshlg
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Re: Thermocoupler Question (v1 vs v2)

Postby walshlg » Wed Apr 05, 2017 4:42 pm

Just to clarify - you twist these with the thermocouple wires and insert in wire nuts?

Jetguy
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Re: Thermocoupler Question (v1 vs v2)

Postby Jetguy » Wed Apr 05, 2017 7:53 pm

All it is is a parallel cap across the input.
A thermocouple makes a tiny voltage proportional to the difference in temperature between the sensing tip and the termination at the thermocouple amp.
A capacitor is what the name implies an electrical capacity or tank if you will. The idea is that in general the extruder heater block cannot change temp rapidly (by that, I mean change 20 degrees in under a second). The wires of the thermocouple act like an antenna and pick up EMI and RFI from the PWM of the heaters, electrical noise, stepper noise, and all that can be greater than the tiny DC voltage of the actual sensed temp. The capacitor smooths this voltage and absorbs and thus dampens and hides these high frequency noise signals picked up on the wires. That way, the amplifier trying to sense this tiny signal hidden in a bath of electrical noise has a fighting chance.
It changes and limits the slew rate. Slew rate is amount of change over time. It takes time to charge and discharge a capacitor and if the size is matched, it eliminates the EMI/RFI noise , because they are high frequency noise, and the actual thermocouple signal is a slow changing DC voltage.

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Vicky@Raise3D
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Re: Thermocoupler Question (v1 vs v2)

Postby Vicky@Raise3D » Fri Apr 07, 2017 5:38 am

We just inserted it into the terminal of thermocouple.
1.jpg
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