• EEVblog #242 – Hakko FX-888 Soldering Iron Hack

    Dave got fed up not knowing if his Hakko FX-888 iron was left on or not. So hacked the LED to toggle RED/GREEN, so it’s always on.
    Toshiyuki Kita link

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      • Manuel


        As nearly everytime, again a very nice video, btw. how long does it usually take to produce such a video of 26mins?

        What would you guess why are they doing PWM on the original led?

        Regards from Germany,

        • http://www.eevblog.com EEVblog

          The PWM is likely just a consequence of the LED output being directly connected to the heater switching circuitry. So it’s not really “PWM” as such.
          A video like that would take maybe a few hours to shoot (I had over an hour of recorded footage, but sometimes I forget to press stop :->), editing takes maybe an hour or two. Several hours to render and upload (but that’s mostly hands-off). So not uncommon for such a video to take most of a day to do. A more complex video like a big review might take several days total.

      • http://headsplosive.com Wartex

        Do you screw up explaining something and shoot it again, or it’s just straight cutting (i.e. no retakes)? I try to make my vids in one shot by rehearsing the whole thing several times.

        • http://www.eevblog.com EEVblog

          I screw up a fair bit, my brain and mouth lose sync often, but mostly I just edit to cut the dead space at start and end of each clip. On a good day every clip will make the cut. I never rehearse. Where are your videos?

      • Wilfred

        At around 10:13 there is a breakup of the video. Seems to be at an edit point. It is only momentary but I’ve noticed it once or twice before, recently.

        • http://www.eevblog.com EEVblog

          Yep, that’s my new video editor NCH VideoPad. Can’t read the odd camera file correctly it seems. Annoying, but with sticking with as I like it better than Sony Vegas or VideoStudio.

      • http://truthspew.wordpress.com Tony P

        I love my MPJA ZD-929C. It’s got all the features and you can tell that it’s powered on without modification. Plus it’s less expensive than the Hakko too.

      • Mike

        Great video. Amazing that they didn’t have it working this way already. My Duratech iron from Jaycar has this type of led system. But if you think it will stop you forgetting to turn it off … well, at least for me it’s a while sometimes before I notice. Lol.

      • http://zpapageek.wordpress.com/ ZPapaGeek

        Hey Dave,
        I had a similar issue on one of my art projects. Being the starving artist, I REALLY KISS’ed a solution. I mounted a 3mm LED between the legs of a 5mm LED. With a little higher current, the small one shines quite nicely trough the large one!

      • Al Martin


      • http://www.island.net/~kdbrown Keithy Brown

        I have the smae unit and the same problem: don’t know how many times I’ve come into my lab in the morning and noticed a quick red flash! I think, though, in my situation, that as well as needing a LED on all the time it needs to be above the huge knob: I find that the knob hides the LED a lot of the time even when it is on.

      • http://www.island.net/~kdbrown Keith Brown

        Can’t even type my own name! Nor the word “same”! As Dave would say…FAIL!

      • Mike

        Dave, a blog of you making a blog is not a bad idea. Kind of a “day in the life” so we can see how much work is involved. Sounds like it is a fair bit of work, not to mention the electronics.


      • Pyr0Beast

        Why not just simply pull-down the red led to ground with 4.7kOhm resistor ?

        Or run a green led in series with the red one ?

      • allan


        Since there’s an internal fuse, you might want to put a flashing red LED/resistor combo. in parallel with the internal fuse next time you have the case open.

      • allan

        ….assuming the fuse carries DC…..that is, might not…..

      • Dan M

        Products designed by Toshiyuki Kita:


      • KJ6EAD

        A similar but simpler modification has been designed for the venerable Hakko 936 for those of us that have that predecessor to the FX-888.


      • http://dics.voicecontrol.ro Dumitru Stama
        • http://dics.voicecontrol.ro Dumitru Stama

          It seems this version of the Blog does not support long and spooky URLs. Here is a short version from Google : http://goo.gl/z4DOQ

      • m3

        I think you can replace the power swich of the station with a iluminated one, I have one at home the same size with the one Fx-888 uses. I’ve searched for an image, this is the closest I have found: http://tiny.cc/zwf5t

      • Richard


        I used the Belkin Conserve socket to power things on my bench for 30min. Presss the button and everything is active. After 30min. it shuts off. 15A rating means it can run most things on the bench.

        I use the same thing on my mp3/phone/accessory charging station.

      • Facundo

        I think a 220 ohm resistor with a green led, at the output of the power supply it is really easy to figure out, a 20 min video of a led modification ? Mmmm.. where are those old good videos ?


        • http://www.eevblog.com EEVblog

          Show us your video then…

          • Facundo

            I wasn’t expected that reply, i was just saying that a whole video of 26 min just to put a led in a solder station, seems to be pointed to other type of guys, i have saw your videos from almost your beginning (rigol) btw i have bought the rigor for your, that was a worth video, like the comparative of the multimeters…

            I mean that were the really good old videos, or showing some equipments functions…

            Is like the big manuals of specifications that you hate from some product, who need a manual to add a led there..

            And how you can be so sure that it is an open collector?

            Anyway good luck…

        • KJ6EAD

          Though I don’t have that particular solder station model, I still appreciate the problem solving process and the effort it takes to describe it.

          Describing it as a failure is obviously harsh and churlish.

      • f4eru

        Are you shure it’s an open collector ?
        Perhaps it’s a push pull output?

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      • P. Marian

        Does this soldering station work on 220V? I want to buy one but it says 120V.

        Offtopic: pls install the “Subscribe to comments” plugin so we can get emails when there are new comments on specific article. Thanks.

      • klee27x

        Hi, Dave.

        I’m not sure if I’m the first to post this, but there’s a much more elegant solution for the LED, if you use a common anode tricolor LED, which are very common.

        Clip the blue cathode completely off the tricolor LED. Clip the green cathode short. Then solder the anode and the red cathode onto the board where the red LED normally goes.

        Short the low-side current limiting resistor. Cut the high side track to isolate the anode from the 9V rail. Solder your current limiting resistor on the high side. Reuse the 2.2L off the board, if you want.

        Solder a wire between the green cathode and ground.

        Assuming the open collector output is CMOS (voltage drop lower than 0.2V), the green LED will light up when the heater is off. When the heater switches on, the green LED will turn completely off and the red LED will turn on. Cuz the FVD of the red LED is abour 0.3V less than the green, and you’re using a common limiting resistor on the high side.

        If the open colector output is a BJT, you might need to put a silicon diode between the green cathode and ground. Or use the blue instead of green.

        Either way, you’re adding at most one diode to the component count. There’s no transistor needed, and there’s no parasitic drain through a base resisor. No parasitic drain through the green LED current limiting resistor when the red LED is on.

        Just swap out the LED, cut a trace, move the resistor, solder the wire. And Bob’s your uncle.

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      • Pete Higgins

        I’m sorry to say this but I think that you’ve screwed up the operation of this circuit.

        It doesn’t make sny sense that the drive to the LED shoud be any sort of PWM signal.

        I would suggest that what is happening is that the output from the control chip is not an open collector output, it’s a standard totem pole CMOS output. This means that when it goes high and turns your FET on, the red LED is connected direcly across the drive signal which shorts effectively shorts it out. This overloads the supply to the control chip and either collapses its supply or activates some sort of protection and turns the drive off again. Hence it oscillates on and off instead of switching on cleanly. This may or may not affect the temperature control but either way it’s not very elegant.

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