know if soldering iron is present using an ir detector based on phototransistor

[amateur_25]

Hi
I already have glued on a long lever switch which the soldering iron depresses. However I just suddenly had a thought that all hot objects give off IR. Hence I was wondering if it would be possible to use a phototransistor to reliably detect if the iron is present? It would be slightly offset from the tip so it doesn't overheat. Would be be susceptible to false positives caused by natural light during the day / light from my lamp at night?

[David_AVD]

Not sure on the passive IR detection, but another possible method is to arrange a modulated IR LED and photo-detector as a beam break setup.

How well that would work will depend on how repeatable the home position of the iron is.

[pickle9000]

Why not mount a thermistor in the holder?

[SArepairman]

the easiest way is to glue a magnet to your soldering iron and to use a reed switch. or two, why buy one when you can buy two for twice the price, so like 50 cents.

[scientist]

Heat is far infrared, not detectable with a phototransistor.

[miguelvp]

Heat is far infrared, not detectable with a phototransistor.

Unless it's glowing hot

But yeah a soldering iron shouldn't get glowing hot.

Edit: of course if it's glowing hot it means you can actually see it with your eyes, heat itself doesn't show on the near infrared as scientists states. But there are far infrared detectors available for cheap.

[bance]

Maybe this post can help you.......

https://www.eevblog.com/forum/reviews/pace-set-back-controls/

Steve.

[han]

Just a question,
Are you detecting the condition of soldering Iron is ON/OFF?
or detecting Soldering iron is present?


for detecting soldering iron present you can use switch (Photointeruptor, Limit Switch,..)
For detecting soldering iron is hot , you can use thermoplie and Comparator:
http://www.digikey.com/product-detail/en/ZTP-115M/235-1332-ND/3974093

[amateur_25]

OP, what exactly is wrong with the original lever switch solution? Are you trying to complicate something needlessly?

Thanks you guys. There's nothing wrong with the lever switch method. I was just curious if I could do it with a photo transistor.  I do like tinkering with stuff it's how I learnt much of my electronics. Still crap though lol. I did initially think of the thermocouple but I didn't have one to hand. I think I'll follow the kiss principle this time and just get it done.

[PointyOintment]

To detect far infrared such as that emitted by hot objects, you could use a bolometer. It's basically a thermopile with one end painted black so that it absorbs the IR and gets heated by it. Being in close proximity to the hot iron tip might also cause it to be warmed through the air, possibly reducing temperature accuracy, though I doubt that would matter for your application.