Circuit's Blog :
Return to Blog100 Seconds Duration On Switch with Touch Control by LM555
Posted Feb 06, 2012 at 1:15 pm
Figure 1
This is a touch controled switch which keeps the circuit on about 100 seconds after touching the plate connected to the 2 numbered pin. At the end of this time duration, relay releases and the circuit gets to off position.
The impedance of the trigger input of the 555 timer IC is very high and the inductive voltage on the human body is enough to trigger it. The circuit works based on this principle. You can use a piece of metal as a plate. The circuit can be used in toy circuits, buzzers or any project that is suitable. You can adjust the duration time by changing the R1 and C1 values.
Comments on this post:
Featured Products
Sullins Connectors
Wire-to-board interconnection options from Sullins feature a wide range of sizes and applications
MCC Voltage Suppressors
MCC’s TVS series high-power suppressors protect sensitive components from voltage spikes and transients
Bourns RS-485 Eval Boards
Evaluation boards that streamline evaluating circuit protection on RS-485 serial device ports
2 years ago: I have built this circuit and it works very fine in our office sliding door. No need to use magnetic cards, just authorized finger prints will do. Thanks a lot!
2 years ago: this could be dangerous because it might be used for making timed bombs! but I hope NOT! Peace!