A few answers.

The great thing about the 555 design is that the oscillation frequency is based on internal ratios rather than internal absolute values. The freq changes very little as Vcc is increased or decreased. The tolerance of the external components usually is the source of the majority of any freq error.

Most small capacitors are marked with two significant digits followed by the number of zeros needed to define the value in picofarads. a .01 uF cap is 10,000 pF, or 10 followed by three zeros, or 103. A .0047 uF is 472, and a 39 pF is 390.

One way to tell that the 555 is oscillating is to measure the output with a DC voltmeter. For a 50% square wave it should read approx one-half of Vcc.

ak

 

I didn't use a limiting resistor.. the output was 4.5v.. didn't think it wa required. led me add a resistor and see what happens..I would like to put a blue led on the power wire so you can see when its got power and a green one the output so you can see it woking

 

oh, and I ngegted to put in the zener. now tats its in, my voltage output is 7.3v....

 

An LED flashing at 30 Hz probably will be seen as steady rather than flashing. What you can do is connect the LED and current limiting resistor to the 555 output with a capacitor, and put a small diode reverse in parallel with the LED.

ak

 

what size cap?

 

ok so I built it on a breadboard and had the results ive posted,, I built the exact same circuit on protoboard and its still squarewave but the voltage goes from 1.8v 35.6v very erratic.. and the freq. is only 20.40hz instead of 30? any ideas?

 

so what number is 0.1uf ceramic and could I use the colored plastic covered kind? ive read them called metal something caps.? I cant understand why the scope is so different when the only changes was the breadboard to the project board..

 

what size cap?

E x C = I x t

C = (I x t) / E

ak

 

E x C = I x t

C = (I x t) / E

ak

example please

 

thanks everyone.. the circuit is built,, tested good on the o-scope and is installed and completely functional..

 

Well done. Good to have a success story.

 

Well done. Good to have a success story.

Thank you very much sir... This is the first one I made it through since joining here.. noe to finish the othe 3 treads I have started here..lol

 

now that its done,, im considering a v2.0 of it,, I want to include a power LED that just comes from the 12v input, but I want to put one on the output to show it working.. I know at 30hz It would appear to just stay lit. is there an easy way to slow the output LED down just to show its functioning? It would make the customer happy.

 

You can use a counter IC such as 4017 to divide down the frequency by 2-10, depending on what you want. There might be a divide-by-16 counter out there, too.

 

Slowing the LED flash rate down will indeed make the output pulsing more visible, but a flashing LED soon becomes very annoying. Better to have it continuously lit (or apparently so, as it would be at 30Hz) if it's only an indicator.