I Need help or advice

[byron]

I firstly just want to make sure that I am going to use the right circuit. I basically am building an on/off timer that I want to trigger on every 30 seconds. I was looking at just using a simple 555 timer as an astable multivibrator. I don't want to use a switch to trigger it, I just want to have it start when I put 5VDC to the ciruit. All I want it to do then is constantly switch on every 30 seconds. Am I using the right ciruit or should I be using a monostable circuit? I also need to be able to change the time that it triggers on every once in a while to maybe a minute. Do I need a relay switch for this ciruit? Also, I am going to add an LED to light up when it turns on so how do I figure out what resistor to use so that I don't burn it. And last question is should I use a transistor in the circuit?

 

[bogdanfirst]

hm....to many questions.....nut not many details.
ok.....the 555 as astable is what you need.
how much time do you want the circuit to stay on?
you can search the net, there are a lot of calculators wich you can use to determine the values of the resistors so that you get the right timing.
just search for 555 timer calculator.....
im sure you will find something.

 

[byron]

Thanks, for the help. As you can see I am a novice in electronics. I guess I just need the time that its on to be a spilt second since I just need it to pulse to the switch box to turn it on. Am glad to just know that I am starting out in the right direction by using the astable circuit. Thanks again. Any other advice that you might have will be greatly appreciated.