We all know that forgetting to turn off the soldering iron and leaving it for a long time on the hobby table can produce undesirable results to say the least.
In order to avoid such situations and to keep the electric bill low, connect your soldering iron to this circuit which automatically turns off
the power line of the soldering iron when you left it in its stand for more then 30 seconds (time allowance is adjustable through P2).
During normal soldering jobs, you must move the soldering iron every now and then to reset the timer and guarantee continued heating.
This principle is similar to the deadman's switch in trains and other SPS controlled machines. The heart of the circuit is the counter IC. Its reset terminal
is controlled by switch S1 which is installed in the soldering stand in such a way that it resets the counter once the soldering iron is placed in the stand.
To switch on the soldering iron one must press S1 thereby closing the relay and starting the counter.
Electronic Circuits volume 1.0 - Circuit Nr. 50
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.