Dilshan Jayakody published a new build:
To keep it simple we choose LM358 dual operational amplifier IC to monitor the 907’s thermocouple and drive the TRIAC. The entire control circuit of this soldering station is powered by single rail 5V DC power supply. To drive both handle and station we use 12V-0-12V 8A step down transformer.
Once calibrated, we may be able to regulate temperature of the soldering iron between 210 °C to 450 °C. As shown in the photograph we construct our final version of soldering station in slightly modified old ATX power supply casing. For this entire project we spent only 25USD, which is roughly 3000LKR at the time of writing.
Project files are available at elect.wikispaces.com
More details at Dilshan’s blog.