555 flashing led

[jimmyflimby]

hi just compleated a 555 ic flashing led the problem is it wont flash any ideas

 

[mneary]

Try another battery.

 

[jimmyflimby]

the led stayes on perminent but does not flah

 

[dougy83]

Post a picture of what you've done or at least a schematic of what you think you've done.

 

[jimmyflimby]

http://www.kpsec.freeuk.com/

 

[killivolt]

Welcome to the Electronics Club

Jimmy do you have a reasonable pic of what you have done ? If your using a bread board you'll want to check and see if all the components and jumpers have a good connection.

In addition to that we would like to see the Schematic, all I see is someone's url.

Edit: And why is this in the Repair Section of the forum? It should be in Electronics Chat or Projects not here.

Good luck on the flashing LED though.

 

[jimmyflimby]

flashing led

this is the project i am working on

 

[mneary]

Did you cut the tracks where the instructions said? Use a meter to confirm there is no stray copper.

 

[earjun]

The 555 is wired as an astable multivibrator.
Check the connection of 1uf capacitor and its polarity.Or try changing the capacitor.

 

[rahul.sadtm]

hello jimmy..

first you put the actual circuit diagram you are working with. And check the frequency of your astable multivibrator. May be its too big that you can not see the blinking...

 

[earjun]

His schematic is here
Stripboard

 

[rahul.sadtm]

as your circuit diagram shows, your 555 timer IC is working in astable mode...to see the clear output keep your output frequency in KHz range.


What values of R1, R2 and C should you use?

R1 should be 1kΩ, This leaves you with the task of selecting values for R2 and C. The best thing to do is to rearrange the design formula so that the R values are on the right hand side:

R1+2R2=1.44/(f*c)

Now substitute for R1 and f :

1+2R2=1.44/(1*c)

You are using R values in kΩ and f values in kHz, so C values will be in μF.

To make further progress, you must choose a value for C. At the same time, it is important to remember that practical values for R2 are between 1 kΩ and 1MΩ. Suppose you choose C = 10 nF = 0.01 μF:

1+2R2=1.44/0.01=144

That is:

2R2=143

and:

R2=71.5 Kohm

work with these values may be you can get better output.

 

[kakin]

Stuff I have encountered when working with 555 timers and flashers:

- Check the timing capacitor, it may be too low value
- Check the timing resistor, too big and not enough current is getting to the cap, even if timing equation is correct
- Check voltage connections, both + and ground
- sometimes you need to add a small value cap to the pin 5 of the timer to gnd (can't remember if its actually pin 5, but it should be in the datasheet)
- if that don't work, try changing the timer IC
- if that don't work, try assembling again in a different board
- if that don't work, check the wires, sometimes they seem fine but are broken inside and don't conduct.
- if that don't work, start over with all new components and run thru the checklist again if it still don't work, maybe the design is wrong or you are wiring something differently than intended.

Good luck!

 

[AllVol]

Using a 555 timer is a very uncomplicated activity, but a very important learning excersize nevertheless.

When first learning to blink a led with a 555, it is important to remember the rule of ones: 1K ohm resistor for R1, 100k resistor for R2, and a 1 uF capacitor. This combination will give a blinking led every time. In fact, on a breadboard circuit thrown together before writing this, my circuit flashed its LED at a rate of 7.142 Hz, according to my oscilliscope.

As is said, your results may vary.

Have fun.

 

[jimmyflimby]

ty all for your help it is appreciated tyvm