555 Timer Rapid Flashing

50 - 555 Circuits

So the best you can do is 2.2 secs with the corner above. Bad news is the circuit uses power at 10mA.

Thank you very much. I will definetly try with that circuit.

Here is the circuit I was originally trying that didn't seem to work:

The only thing I did differently was I used a 100K resistor for R2 instead of a 470K because I didn't have a 470K.

I didn't think that would make a huge different, but I'm not an expert on 555 timers because I've never used one before.

Thanks for all the good advice. I try again with the suggested circuit and see if it works.

Pin 3 is output and the LED looks backward. Also the LED should go to gnd.

Pin 3 is output

I think you'll find Pin3 is a digital output, so it should go low when in the OFF state.

http://www.555-timer-circuits.com/using-the-output.html

I see nothing wrong with your schematic.

What is the value of C1, and if it is an electrolytic did you have the - side to ground ?

It is worth adding a 1nF or similar across pin 5 to ground ... think of it as insurance.

For any digital circuit it is always a good idea to add a 470uF -1000uF capacitor PLUS a 100nF (0.1uF) across the supply rails close to the chip to stop the spikes causing unwanted issues.

Mark

The schematic I found on some website with a little bit of instructions but they didn't give a value for C1.

So I put in a 100uF capacitor (I don't think it was electrolytic) because that was what I had a easiest access.

So I put in a 100uF capacitor

100uF will be a polarised capacitor of some type.

Double check you have it the correct way, and if possible change it just in case it is leaky. 

If you do the calculation that was supplied earlier it runs at 0.0153Hz

http://www.daycounter.com/Calculators/NE555-Calculator.phtml

or from here http://web.udl.es/usuaris/p7806757/555-calculadora/555%20Calculator.htm

It is ON or Off for 32 secs.

so you can see how useful the 265 million hits are to resolving why it might not work the way you planned.

Mark

Thanks.

I did try the capacitor both ways but I may not have waited 32 seconds, so my problem might have been caused by impatience though I believe I left it for long enough.

I'll try again and see if it works once I have time.

Thanks.

I did try the capacitor both ways but I may not have waited 32 seconds, so my problem might have been caused by impatience though I believe I left it for long enough.

I'll try again and see if it works once I have time.

I did try the capacitor both ways but I may not have waited 32 seconds

It is a long time when you think it should flash rapidly. ...

The lack of capacitor across Pin5 could also increase the time by a factor of 10...

If you try different values for R2 in the second link, swapping the 470k for 12k gets you a 0.9Hz flash.

You can always add a 12k across the 470 to try it ...it will check your circuit does work.

Mark

Thank you guys so much.

I tried Clem Martins Circuit and it work exactly as it was supposed to.

I don't know what I was doing wrong originally (I think it was the pin 5 control wasn't hooked up right, but I don't know) but it works now.

Thank you all so much. I thought I was doomed to never have an IC work for me because a have a couple of and, not, and or gates, but I couldn't get them to work either (but that is a problem for another time).

Again, Thank you all.

That's great you sorted it, and learnt something along the way ...

Perhaps you could mark Clem's answer correct and any others you want as helpful.

Mark