Soldering iron indicator mod

At first glance, [sprite_tm]s weller mod seemed a bit trivial. In reality, it’s like art with analog electronics. He wanted to add an indicator light for the heating element. To pull it off, he built a funky diode capacitor circuit to create a pseudo-regulated DC voltage, then used a zener diode, a potentiometer and a transistor to make a simple voltage switch that activates a transistor driven LED.


  1. Dax says:

    Yeah but once you have taken your soldering iron apart to do the mod how do you solder the circuit together?…

    lol, just kidding.

  2. steve says:

    another load of usless crap roll on xmass

  3. Wolfmankurd says:

    lol cool, I’d like this but maybe a smaller version

  4. ... says:

    Neat hack, I can vouch for those old magnetic switches being unreliabe as heck… My old station would kick out every once in an while; I decided to get a new one when it stoped turning the heater off, and pumping the full 50w into the element all of the time, giving the tip a healthy orange glow…

    I picked up EC2002 off ebay for about $30 shipped (it had a loose contact in the connector, the last job for the old station was resoldering the connector).

  5. Bones says:

    At least with mine, the base station clicks, which tells me there’s a relay in there. I have a feeling that would be a lot easier to take an on/off signal from.

    But whatever works, and it’s an interesting circuit.


  6. fbz says:

    ok now i want one that sends an email to my phone telling me “just turn it _OFF_ and _WALK AWAY_” when i have left it on and walked out the front door. how many tips have i killed by leaving my poor soldering iron on eleven?

  7. jeff says:

    opening the base unit can be done by removing the rubber feet and finding four screws. There is no need to pry the case open with a flatblade screw driver. I like the hack simple useful and informative :-) Another coloured LED on my bench blinking on and off impressing visitors :-)

  8. Pedro says:

    OK, the soldering iron is off….. so I…. turn it on and just walk away!

  9. Josh says:

    Nice mod. Luckily I have a Hakko which already has a heating indicator LED. Oh and these puppies can be found

  10. Perry says:

    A simplere solution is to simple wind a coil of wire around one of the secondary wires, then connect each end to and LED with a very low forward voltage bias. When current flows through the heater, the coil of wire acts as a current clamp and generates a voltage like a secondary transformer coil, which then lights the LED.


  11. akmixdown says:

    @5: the Weller WTCP series don’t have a relay; it’s the tip that is clicking, as the modder correctly describes.

    @1: You don’t have more than one soldering iron? :-)

    @9: Yes, that is an awesome idea, I may just do that with mine!

    oh, and Will — “a funky diode capacitor circuit to create a pseudo-regulated dc voltage” ?? You mean a half-wave rectifier? :-)

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