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.

[tooby]

(paused at 11:28)

Why not get a common-anode RGB LED (common as muck) and, um, snip off the blue leg?

Bingo! You now have a common-anode red/green LED!

[ixamraxi]

I think my favorite part about this video was that you stressed the how and why you had the resistors and couldnt get rid of them without changing components. Thanks for taking the time to make the video!

[craggslist]

But how do you solder inside a soldering

[tawfiqtube]

When Dave is sleeping, his supercap is charging, when it is fully charged and driving the base current of the transistor, he wakes up in the starts to lunch is acting like a resistor and resisting him from mean Dave, you sleep electronics, eat electronics, you work you man!

[EEVblog]

@TwoToBeamUp Well, it's not actually PWM as such, just likely the direct output from the heater switcher which will be pretty random.

[sootpig]

Why not keep it simple? Use a 10K? or so from the cathode to ground, so that the LED glows dim when the unit is on, but flashes brighter when the heater is on. Swap the 2k2 for a 3k to stop too much current flowing through the LED and bam, 2 resistors and you're good :)

[RicardoATBarbosa]

Dave, as I'm a Brazilian my first language is not English. Thank you for letting me know these expressions: "rarer than hens teeth" and "bob's your uncle". We learn more than electronics here!

[andrewkowalczyk]

Elegant hack, you ought to do more of these

[mikeselectricstuff]

There's an easier way to get a red LED to override a green one, using the lower voltage drop of the red. Resistor from positive to anode of both LEDs, cathode of green to ground, cathode of red to the switched pin. When pin is high, green is on. when red turns on, the voltage across the green is then too low to light it.
Another easy hack for this iron would be just a second resistor from the LED cathode to ground, so it lights dimly for 'on', and brighter for 'heat'.

[EEVblog]

@LapsusAntepedis It was part of a live show, don't recall which one. Wasn't a normal teardown video. I don't have any private or deleted video. I've never put up a video and then permanently removed it.

[EEVblog]

@keenantims Yes, I see the 936 schematic now. The FX888 uses a bigger pin count chip. Perhaps it's still doing something weird with the LED, I didn't trace that far.

[millenniumf]

Man, I love your videos! This one reminds me how much I love my Weller soldering iron's indicator LED. It goes sold on when you've switched the iron on, then when it reaches the temperature you've set, it blinks. Then when you switch it off, the LED goes off. Just an awesome, not too expensive iron.

[urdnal]

I bought an FX-888D (same as in the video but with digital display) on his recommendation. One night I was at the bench tired. Went to bed and didn't notice I left the iron on until the next evening. About 22 hours at +650° F and if you'd told me it was 22 minutes I wouldn't have been able to tell. Probably not good to repeat it, but things like this show it's a quality product.

[Bokononistly]

I love your catch phrases. "That's good enough for Australia!" "Bob's your uncle"

[ralvarezb]

About the led question at 1:00, they aren't the only. Even some workstations of Weller or metcal have a single led too

[EEVblog]

@koktelici Farnell stock it in Oz. No, I don't believe it is tapped, just the top PCB is designed to fit different transformers.

[EEVblog]

@keenantims Just looked at the 936 schematic. Yes, that's rather tricky.
The FX-888 uses a single bigger pin count device, so who knows what it's doing with the LED? Is it just a consolidation of the existing design into the one chip, or something new?

[EEVblog]

The switch is on the side of the unit. Not visible at all in it's position in my lab.

[klystron]

Did this over twenty five years ago on a Weller using a dual red/green led do not need the complication of extra transistors as the red takes over from the green which represents power on and red is iron heating. Good design is simple!

[EEVblog]

@kevtris I couldn't find any common anode red/green or RGB LED's in Australia.