Simple and cheap DIY induction soldering station

[fireworks]

  Here is a video which shows a very cheap way if creating a DIY induction soldering station:

   

  The main idea is to use a normal, very cheap, Chinese soldering tip which are made of steel, therefore will heat up when exposed to an alternating magnetic field.
  Then it uses a switching circuit similar to a switching power supply, therefore the generated frequency is a few hundred kHz instead of 13.56MHz used by a Metcal station.
  This lower frequency allows one to avoid using a coaxial cable but a simple pair of wires can be used instead.
  All these make possible a very low cost DIY soldering station using very low cost tips.

[fireworks]

  The circuit presented in the video has several drawbacks:
    -claimed to output 25W but the real output to the inductor might be less
    -heating time of about 30s instead of 5-10s for a Metcal station
  However the power can be increased and the heating time reduced easily by using a better circuit than the one shown.

  Another drawback is that the Curie point of the tip is probably uncontrolled.
  However,  the temperature can be controlled by varying the power put into the coil. The cheap Chinese soldering irons that use those tips have temperature sensors inside.

  In my opinion, the easiest way to build a usable DIY induction soldering station based on this idea is to use a Chinese soldering iron and:
   -add an induction coil to it
   -use its temperature sensor
   -build a better (but still simple) switching supply to feed the induction coil regulated by the voltage from the temperature sensor

  Any thoughts ?

 

[MosherIV]

I think you are confusing simple inductiin heating with the rf skin effect that metcal/thermatronics/hakko use.

This simple induction system simply induces a large current in the tio to heat it up.

The metcal (et al) runs at rf frequencies so that the ac current runs along the skin of the tip, the current must return via the core, where the current transitions from the skin to the core it must travel through a change in material (the tips are plated). The plating or the core have magnetic properties, hence when heated beyond the curie point the heating stops until the magetism returns. Totally different from just generating  a large current to heat up iron.

[fireworks]

  Yes, there are some differences.
  But they don't matter much: induction at lower frequencies (hundred of kHz) works well too.
  Actually Metcal offers induction soldering stations working at 450kHz:

    http://www.okinternational.com/hand-soldering-systems/id-PS-900/Production_Soldering_System_-_Tip_Hand-piece

  What I tried to convey in the first post is that the guy's idea of using cheap iron/steel soldering tips not originally designed for induction heating is a valid one.
  My idea on top of that is to repurpose a regular cheap Chinese soldering iron and its tips and adapt it for induction soldering by adding a coil close to the tip.
  The switching frequency would still be in hundreds of kHz.

  Any thoughts about that ?

[LaserSteve]

How much coupling to any nearby loop structure when soldering?  I like my magic smoke to remain contained.

Steve

[fireworks]

  It's not a problem for the commercial induction soldering stations working at either 13MHz or 450kHz.
  In the worst case, it can be solved by shielding.

[MosherIV]

I just looked at the link, the PS900 is not an induction soldering iron. It uses the material transition technique that I descibed. The PS900 is decribed as using 'smart heat' technology, search for the term, Metcal do a promotional video explaining it.

The advantage of generating the heat at the material change is that the heat is generated where is is needed. Other soldering irons which heat far away from tip suffer thermal lag. Hakko and JBC try to overcome this by placing the heater in the tip as near to the tip as they can but they are still not as good as 'smart heat'.
Induction heating will have the same problem

[fireworks]

I just looked at the link, the PS900 is not an induction soldering iron. It uses the material transition technique that I descibed. The PS900 is decribed as using 'smart heat' technology, search for the term, Metcal do a promotional video explaining it.

The advantage of generating the heat at the material change is that the heat is generated where is is needed. Other soldering irons which heat far away from tip suffer thermal lag. Hakko and JBC try to overcome this by placing the heater in the tip as near to the tip as they can but they are still not as good as 'smart heat'.
Induction heating will have the same problem

  It's interesting that you say the PS900 is not an induction soldering station. As I see it, it uses an alternating magnetic field to heat the tip, therefor it is an induction soldering station.
  By the way, at the heart of the Smart Heat technology is heating by magnetic induction.
  Care to explain your position ?

[MosherIV]

If 'smart heat' is just induction heating then there would not be temperature regulation by curie point effect. Induction heating temperature would have to be electronically controlled.
Metcal, Hakko and Thermatronic soldering irons do not have any temperature control electronics, it is purely done by curie point effect by the tip.

As I keep saying, the heat in 'smart heat' is generated at the material change (plating to core) so that the heat is literally generated at the tip NOT in the core. Induction heating would heat the core material and rely on thermal conduction to get the heat to the tip.

Edit: this explains it better
https://electronics.stackexchange.com/questions/113339/metcal-why-do-they-heat-with-hf