eric, i built the circuit you drew,but why is the LED keep staying ON? i mean it blinks but it keep staying and turns off for a second and on again.., i thought it would stay off and turn on after a limited time(as capacitor value).. U got what i meant?
eric, i built the circuit you drew,but why is the LED keep staying ON? i mean it blinks but it keep staying and turns off for a second and on again.., i thought it would stay off and turn on after a limited time(as capacitor value).. U got what i meant?
hi Z,
Its an Astable [oscillator] so it will flash On/Off at a slow rate.. the 10K/1K and 100uF set the ON and OFF periods, 10 times longer ON than OFF [ approx]
Yes, you can trigger a 555 timer simply by touching pin 2. Here is a touch sensor circuit for the 555. The timer is wired as a one-shot (monostable), and the value of the capacitor and resistor control how long the output stays on after you let go:
**broken link removed**
You can also add another 555 timer to make a bistable switch, which keeps the output on indefinitely when you touch the trigger and then let go:
Also, if you want a touch-on-touch-off, you can add in a 7474 flip-flop:
If you're interested in making a touch switch, here are a few ideas to go on.
I hope this helps!
Regards,
Der Strom
EDIT: In these circuits, it also couldn't hurt to have a pull-up resistor connected to pin 2 as well. This will prevent false triggering. 100K-500K should be good, but feel free to experiment a bit.