Cold Heat Soldering Iron ?

[Nigel Goodwin]

Even so, why a device with only 4 alkaline batteries can melt solder is hard to understand. I did used a similar device in work but that works on Ni-Cd batteries instead.

Alkaline batteries will 'self limit' the current, NiCd's will happily provide enough current to destroy themselves, as they have an extremely low internal resistance.

NiCd's would require some kind of external current limit (resistor of some kind), which is going to get HOT, rather spoiling the 'cool' feature of the device.

As a matter of interest, I just tried holding a piece of solder across a single AA Duracell, within a few seconds it was warm enough to make ne let go :lol:

 

[eblc1388]

What I'm try to say is alkaline batteries, because of its internal resistance, might not have the required current to heat up the solder between the electrodes that is a small distance apart, as the voltage drop across the solder is small and power=V.I.

Actually, I suspect there is more to just 4 batteries+a pair of electrodes inside the device. There could be some converter involved.

 

[Nigel Goodwin]

Actually, I suspect there is more to just 4 batteries+a pair of electrodes inside the device. There could be some converter involved.

What we need is someone to take one apart!. Even measuring the voltage coming out of it would be helpful!.

There certainly could be a switchmode converter inside?, lowering the voltage and increasing the current.

 

[audioguru]

Someone on another site has one and says that its heater tip is divided in two halves with a gap. When the joint or solder bridges the gap then current flows and the tip gets hot. The very small size of the heater tip allows it to heat-up and cool-down quickly, but is too small to solder anything big.
The user says that the tip is fragile (he dropped the iron and the tip shattered) and very expensive.

 

[pebe]

This sounds very similar to an instrument used by a company I used to work for. It was custom made in-house for soldering coax cable joints in TV cable networks over 40 years ago. The work was all done at facia level on houses so portability was of the essence.

The two electrodes were carbon and the device was powered by a lead-acid motorcycle battery slung over the shoulder. The heat was generated by the contact resistance between the copper cable and the carbon bit. I imagine the device you are talking about works in the same way.

 

[TV-Engineer]

I have one of these and opened it up before long out of curiosity as the makers claimed advanced IC circuitry being involved in the iron's workings.

The batteries are directly connected to the two halves of the tip, with the on-off switch cutting the positive. The advanced circuitry is solely involved with the LEDs - Much like Sir Clive Sinclair's LED torch which uses IC control to (apparently) mean that the batteries inside will probably outlast the person using the torch. I have one of these torches and so far so good, it's bright enough for when the mains has just gone and you want to find the candles and despite using it a great deal, it's still going strong - this circuitry seems to do the same thing, stopping the LED light which comes on when soldering from draining the battery too much.

It is in no way connected to the tip, though, I double-checked that. It's simply 3V going straight to the tip halves. From what I understand, as the voltage passes through the two halves (when something shorts them out), the high-resistance material from which the tip is made heats up greatly.

So, it's high resistance turning electrical energy into heat. Like a standard heater element, but using some newfangled material with funky properties.

 

[audioguru]

the high-resistance material from which the tip is made heats up greatly......So, it's high resistance turning electrical energy into heat.

A high resistance needs a high voltage to heat-up. With only 3V available, it must be a fairly low resistance. :lol:

 

[eblc1388]

So, it's high resistance turning electrical energy into heat. Like a standard heater element, but using some newfangled material with funky properties.

No wonder my 50A experiment have failed. There is no high resistance path in the circuit.

 

[TV-Engineer]

the high-resistance material from which the tip is made heats up greatly......So, it's high resistance turning electrical energy into heat.

A high resistance needs a high voltage to heat-up. With only 3V available, it must be a fairly low resistance. :lol:

Sorry, my mistake there, a case of dodgy memory. It's actually put like this by the makers "an unconventional resistive material named Athalite™, whose physical properties allow it to create heat from low sources of power supply"

So my previous post should have just said that the resistance of the tip seems important, not that is was high-resistance. Of course, I could be clever and say that I meant high-resistance in relative terms, high in reference to the 3V supply voltage... :lol: :wink:

 

[mahinda jayasinghe]

I got the basic principle behind it. This is high current welding.
It is using in can or barrel welding industry. Two mettel weld itself together. This is the way used to male barrels with large metal sheets.

 

[audioguru]

It doesn't weld. Welding needs a very high current that the little battery cannot provide. Solder melts at a temperature that is much lower than melting welding rods, so the soldering iron uses a tiny heater, and two contacts at the tip. The heater uses battery power to heat-up only when the circuit joint or solder joins the contacts. Therefore the battery lasts longer.