not working it will switch it off automatically. This can be achieved on maximum sensitivity of the peizo sensor and placing the peizo sensor on your table or on the soldering iron stand. The sensitivity can be increase or decrease by adjusting the 1M variable resistor connected at the base of the Q1. For less sensitivity remove the 1M resistor connected between the 1M variable resistor and positive rail.
On low sensitivity the circuit will work as a touch sensor for your soldering iron stand and soldering iron and it will activate the soldering iron when you touch the soldering iron or its stand. Hence it will automatically switch off the soldering iron in intervals when it is not needed. The circuit is a power saver it will save your electricity and also extend the life of your soldering iron.
Working of the circuit is straight forward, when it will sense a touch, knock or vibration it will activate the relay switch (and soldering iron connected with the relay switch) for 10 to 15 or more minutes and after that time is over it will automatically off the relay / soldering iron until it will sense the next touch, knock or vibration. The switch ON time can be increase or decrease with the 1M variable resistor marked "Timer Selector". For best results place the circuit in a suitable enclosure and attach the blank side of the peizo sensor inside the enclosure. Use some kind of glue at the sides of the peizo to properly fix it in the enclosure.
The figure below shows a very useful project of a touch & knock sensitive smart soldering iron timer. The circuit will automatically switch on soldering iron for a preset time period when it will detect a touch, knock or vibration.
It can also be adjusted to detect when you are working with your project and switch on the soldering iron and when you are
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