Help needed.

[Izzy]

Hi guys, I'm looking for some help.
I managed to get hold of a 'Fuse' clamp to join filaments, but it's not fully functioning and I want to repair and improve it.
I need help first identifying this part to replace it, it's a heater running of EU mains voltage positive to one side, negative to the other, it's 8.5mm diameter by 17mm long.

I want to replace the simple on/ switch and put an line component to be able to control the temperature, as well as an on/off switch. Electrics isn't my forte so any suggestion helpfull.
Cheers Izzy

[jonnybischof]

The heater goes directly into AC mains? No 12V or 24V power supply in between?
That makes this thing kinda dangerous.. Make sure it's well electrically insulated before you plug it in.

You can use any switch that is rated for 240V (or more) AC voltages. That is the simple part.


If you want to control temperature, you need a triac (wikipedia) in order to switch the power using some control signal. Note that you can't use a reprap's PWM signal here, because the triac will only be able to switch off when the AC signal is at a zero-crossing. This characteristic will break pretty much any PWM control signal, unless you can make a PWM that is specifically designed for use with triacs.

TL;DR: You need to use bang bang heater mode, not PWM.

I must admit I've never used a triac before, nor even took a closer look at them at all. I generally avoid having to mess with AC voltages and work with DC all the time...
It is however not a difficult thing to do. Just need to find a resource on how to use an Arduino to control a triac.

[martin-bienz]

uuh... directly into mains, I would second Jonny's opinion. You will need to ensure everything is really well enclosed, insulated, otherwise it's going to shock you sooner or later (and let's hope that your FI / RCD switches quick...).
Do you know how hot it goes? Maybe you don't even need to regulate / control the temperature?

Otherwise look at this project I came across some time ago:

[Izzy]

Hi Martin, yep that's the one the project has been abandoned and you can't get them any more which I'm not supprised by as it wouldn't meet regulations, but I managed to get hold on a 2nd hand one. They are very poorly constructed, I want to reconstruct it but safely. I need to know what this type of heater is and how I can control it safely to control the temperature and then be able to fuse filaments together.

[jonnybischof]

Well, if it can prevent you from losing your job, I think it could have had more success as a lucky charm

[Izzy]

From the origional Fuse clamp video, it's was supposedly self regulating or maybe it's limited to about 200'c, but it plugs straight in to the mains so approximately 220V AC. EU, it had a simple rocker switch, and the heater is inserted into the ptfe block, it could be that the 240V AC here in the uk was a bit much as it blew the fuse after 15 seconds
If I can identify the type of heater and a method of controlling it then I may be able to get it up and running again safety.

[martin-bienz]

Well, it say's:
"For the heating power had to use PTC resistors "Possitive coeficcient temperature" Get samples, and adapts to rest of the set. These resistors are self-regulating so it is not necessary to control its temperature."
I have actually never used one of those thermistors myself. They increase resistance if the temperature increased (sort of self regulating heater)... but I could not find any details.

220 / 240 (most of the uk) should actually not make such a difference? Don't you have 230AC in the UK?

[Izzy]

Cheers Martin, looks like that's the cookie, the central ceramic plate on mine has broken so that's the main problem, I'll see if I can find a replacement or an alternative.