This is what's inside a typical 24V 50W soldering iron heating element. I actually thought it was going to be simpler than this, but it's quite impressively engineered.
The construction is basically a ceramic core and outer ceramic sleeve. The core has three small holes up its full length and these are used to insulate the wires for the thermal sensor and heating element from each other. The thermal sensor is a common thermocouple composed of two dissimilar metals fused together at the tip of the iron. These generate a small voltage that relates directly to the tip temperature. I estimate that at a typical iron temperature of 350 degrees the sensor will produce a voltage of about 14mV which is monitored by an op-amp in the controller.
The heating element itself is wound round a short section of the inner ceramic core near the tip and terminated by simply running the same resistance wire to the connection PCB in the soldering irons handle, but also running it with a compatible but much lower resistance wire that is twisted along the full length that isn't intended to heat up. This seems to be a common way to terminate heater wires, since it provides a low stress connection.
The inner core with heating element and thermocouple are then slid into an outer ceramic tube and sealed at both ends with a ceramic paste. The protruding wires are sleeved with a high temperature sleeve and the ceramic paste is also used to glue them in position.
Although the irons element is rated at 24V the transformer winding that feeds it is rated over 30V to allow for losses over the opto-isolated triac that switches it and the resistance of the thin cable to the iron itself.
The construction is basically a ceramic core and outer ceramic sleeve. The core has three small holes up its full length and these are used to insulate the wires for the thermal sensor and heating element from each other. The thermal sensor is a common thermocouple composed of two dissimilar metals fused together at the tip of the iron. These generate a small voltage that relates directly to the tip temperature. I estimate that at a typical iron temperature of 350 degrees the sensor will produce a voltage of about 14mV which is monitored by an op-amp in the controller.
The heating element itself is wound round a short section of the inner ceramic core near the tip and terminated by simply running the same resistance wire to the connection PCB in the soldering irons handle, but also running it with a compatible but much lower resistance wire that is twisted along the full length that isn't intended to heat up. This seems to be a common way to terminate heater wires, since it provides a low stress connection.
The inner core with heating element and thermocouple are then slid into an outer ceramic tube and sealed at both ends with a ceramic paste. The protruding wires are sleeved with a high temperature sleeve and the ceramic paste is also used to glue them in position.
Although the irons element is rated at 24V the transformer winding that feeds it is rated over 30V to allow for losses over the opto-isolated triac that switches it and the resistance of the thin cable to the iron itself.
Great !
You can't smoke heating elements c'mon
Can you tell me where to find an element that is 23 volts and 70 watts, I can’t for the life of me find one that will fit my well let Wep 70 handle.
Thanks 👍
Boa noite irmã boas esse comentário fosse traduzido em português que em inglês eu não tô entendendo nada
I've gone through three soldering irons one from from walmart, next time I buy one i'm getting the protection on it. I've made two "apocalypse style" soldering irons from the two that died on me. They are basically cordless and you heat them to cherry red with a torch and it does work but doesn't last long.
I've torn the two irons down and found a very thin wire which serves as the heating element with about 120 turns of wire connected to another set of twisted wire which runs to the electrical connections. The iron tested open for continuity.
Hi, very interesting video. Clear, no background music and very illustrative, thanks for sharing. I don´t have the schematics so I would like to confirm: in my iron element there´s a fifth cable, conected to a spring which sorrounds the ceramic package, is that an earth connection ? Regards
I have a basic 60W soldering iron and the element sometimes only lasts a few minutes.
What is going wrong here? Surely elements should last longer.
On the heating element on mine only one end had another wire twisted together and spot welded, the other end it looks spot welded to another wire going to the electrical connection without a twisted connection. Is there a reason only one end is twisted together with another wire and not both?
How exactly is the temperature controlled? Is there a constant 24v that is pulse controlled or is the 24vac altered like a dimmer?
you're upside down man! what the devil is going on?
I have one of these china specials and my issue is the tips don't seem to make good contact with the heater… and by "good" I of course mean… none… Measuring it the tip of the heater is a good 4 or 5 mm from the end of the tip when assembled and with a fraction of a millimeter gap all around, I found I had to pack in some tin foil, and wrap the heater with foil also or else the tip itself would barely heat up.
This is using the tips provided and I can't possibly imagine this is normal. Since the issue was first noticed the ceramic had become black and almost like charcoal, I assumed this is because it had over heated trying to get the tip upto temperature, and just today became so brittle it snapped off while trying to swap tips.
So… is this the heaters fault somehow being too short and narrow, or the tips fault for being too wide and long… or is it the usual case of "who knows, its a cheapo chinas job, you're lucky it worked at all"?
Thank you. I now have the confidence to buy this brand. I have always been a gear snob. Can't bear the price anymore.
can you offer some advice on what type of element would i need to get a low temp of 90 to 100 degrees. possibly something i could set up to be battery operated. thank you
I have a Zeny SMD soldering station, it's a decent station. I ordered a few extra soldering iron, I thought any 5 pin female soldering irons would work, but when they are hooked up to the station, it doesn't detect a temp sensor, it reads 0/1 and the iron gets very hot. Im trying to figure out how to rewire it, or if they where assembled improperly these are cheap irons.
Do you watch the TT?
Best… Soldering iron breakdown… Ever. Thanks so much for sharing your findings.