This project is for a temperature controlled soldering station built from off the shelf parts.
Other than the soldering iron, the circuit uses only three main components - a PID temperature controller, an SSR (solid state relay) plus a transformer.
A demo video has been uploaded on YouTube:
https://www.youtube.com/watch?v=2xhOkq0snIo (https://www.youtube.com/watch?v=2xhOkq0snIo)
Complete details on how to build the unit plus links to the support videos for setting the initial parameters and fine-tuning the unit are found at this link:
https://pcbsmoke.wordpress.com/2015/07/ ... g-station/ (https://pcbsmoke.wordpress.com/2015/07/12/diy-digital-soldering-station/)
It works pretty decent considering it was just basically assembled from stock parts.
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This is the schematic.
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The unit uses a 24 volt, 48 watt Solomon replacement iron for an SL-30 soldering station. Basically it should work with any 24 volt soldering iron with a K-type thermocouple sensor.
I want to thank Arhi for giving me some good advice on selecting the right transformer:
viewtopic.php?f=56&t=2457&p=60993#p60993 (http://dangerousprototypes.com/forum/viewtopic.php?f=56&t=2457&p=60993#p60993)
The transformer would have to handle 2 amps because that's the current that a 24V, 48W soldering iron would require. I experimented with a few different ones.
First I tried two inexpensive 40VA transformers in parallel. One 40VA transformer was only rated at 1.67 amps so I thought I would try parallel transformers to see if I could get double the current capacity. No such luck! One transformer got hot and the other one stayed cool. That was a bust.
The next transformer I experimented with was a 50VA model which was rated at 2.08 amps. I thought that it would work because the soldering iron would only draw 2 amps. But the secondary voltage under load on the 50VA transformer was very low - only 20.0 - 20.1 volts. That put the current at 2.39 - 2.4 amps. I blew out the transformer!
I found an inexpensive 75VA transformer. I was also experimenting with coupling the SSR to the primary. The SSR specification had a voltage drop of 1.6 volts and as a result, the voltage was lower when the SSR was coupled to the secondary. Coupling it to the primary also stressed out the transformer. I settled on coupling the SSR to the secondary.
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The enclosure cutouts were drilled and shaped and then the parts were fitted into the enclosure before final assembly.
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The PID controller was inserted into the cutout and pressed in all the way until the tabs clicked into position.
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The chassis final assembly.
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