555 timer false triggering..?

[david90]

look at this circuit
**broken link removed**

when the wire between pin 2 and the momentary switch is long, shaking the circuit board trigger the timer. How do I prevent this? If there is no wire between pin 2 and the switch, no false triggering occurs. Also there is no false triggering if I connect pin 2 to +v but I rather not do this.

 

[is_razi]

use a debouncer and a low passfilter .

 

[alphi]

Pls ref it:

 

[david90]

"use a debouncer and a low passfilter"

pin 2 is not touching anything except groud when the button is press. The false triggering happens when pin 2 is not connected to ground.

What is low pass filter?

 

[pico]

Use a small C (10nF) to connect pin 2 and ground.

 

[cherrytart]

getting noise when you move a wire can be triboelectric effects (the insulator becoming a capacitor when it looses contact with the wire, carrying off a charge which then causes noise as it nears or touches the insulator again, for example) which can be diagnosed by changing the wire quality.

more likely though, it is electromagnetic in origin, a twisted pair run to the switch and grounded at the 555 will reduce it, however the capacitor from pin 2 to ground is the best place to start and is probably your fix

 

[Fragrance]

hi

here is the proper solution for your problem this must work fine for you

see attachment

 

[Noman Yousaf]

i also faced this problem some time before.
I noted that pin 2 shloud not be opened(float).
you must pull it up by connecting a resistor of 10k between pin 2 and +v.
if the distance is longer then 1 foot. then you have to use a relay . connect com. terminal of relay to pin 2 and N.O terminal to gnd. (But still use pullup resistor).
now if you give the supply to relay's coil, it will be energized and connect pin 2 to gnd.
now you can use long wire for supplying the relay more the 1 foot( it could be 100feet).

 

[david90]

that's what I did and it seems to work. I just connect a resistor between 5v and pin 2 then a switch between pin 2 and ground.