Hey Guys,
I just built the circuit on the right. How could i modify it
to use a Normally closed trigger.
Thanks,
Haxxx

 

Hello,

I am a newbie. Just built a 555 circuit. I used a relay switch from the output to power a motor. The timer sets how long my output will stay on, then it goes off. I also discovered that moving the opposite relay pin delays how long the output is off, then the timer turns it on (and it stays on).

I don't know if this observation will help you or not. But people have been so generous with their knowledge that I am eager to contribute.

Jeffrey

 

Use the left circuit and switch the position of the push button and the 47K resistor.

 

Correct me if i'm wrong but i think the problem with the one on the left
is that the output doesn't go low if the if the trigger isn't returned to its orignal state. I want a normally closed one shot that will still timeout
if the trigger is held open.
Thanks
Haxxx

 

If you replace the 47K resistor with the NC push button and the NO push button with a 10K resistor it will work.

 

If this is what u meant i tried it,
It doesn't timeout unless you release the switch
Maybe i'm missin suppm, I don't know.

 

That is true. This is the reason you use a push button, you press it once as to trigger the 555 and then release it.

 

The actual trigger will be a photobeam with normally closed contacts.
I was trying to avoid using a relay to get normally open.
If an object is accidentally left between the sensors them my circuit won't time out.

 

Use a transistor to invert the output from the sensor.

 

Hello! I need to know how to build a simple (very simple, please, I'm 14!) timer that switch on a buzzer after 5 seconds it's powered by a 9v battery...
It's my first circuits and I anything about ne555 timer...
Thank You very much!

 

Hello! I need to know how to build a simple (very simple, please, I'm 14!) timer that switch on a buzzer after 5 seconds it's powered by a 9v battery...
It's my first circuits and I anything about ne555 timer...
Thank You very much!

First do not hijack others posts, start a new threat if you want help.

You can use the circuit in figure 2 here:

http://www.eleinmec.com/article.asp?4

Replace the trigger button with a 100nF capacitor and connect the buzzer between pin 3 and Vs.

 

I'm very sorry for my mistake...
I will thank you for the guide-line and the url: I go to watch surely soon...
Thanks a lot...