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Topic: 555 timer beginner circuit help (Read 9267 times) previous topic - next topic

funkyguy4000

Hello,

I am the IEEE Project Coordinator at my university and I am trying to teach beginners to electronics the concept of bread-boarding and how to use the 555 timer.
Now I consider myself a pretty knowledgable person in electronics and this is why I'm kind of annoyed.

I was going to show them this circuit , http://www.555-timer-circuits.com/bi-polar-led-driver.html but for some reason it just isn't running. I have it wired up like the image but it just won't run!

Any help?
Accelerate to 88 miles per hour.

TeslaIaint

Have you tried swapping parts out or even swapping out the breadboard? I know from my school days that students often put bad parts back in the parts drawers. It shouldn't take long to completely start over with new parts.

funkyguy4000

Yup, everything has been tried with new parts, even the power supply
Accelerate to 88 miles per hour.

cmiyc

Make sure the 33K is connected to output, not 9V.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

nickgammon

I made up that exact circuit, and it worked. Both LEDs flashed. Only one flashed when powered with 5V.

Quote
it just isn't running


What do you mean? No LEDs flash? Just one? One or both on all the time?
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

funkyguy4000


Make sure the 33K is connected to output, not 9V.


Roger that, yuuup its connected properly


I made up that exact circuit, and it worked. Both LEDs flashed. Only one flashed when powered with 5V.

Quote
it just isn't running


What do you mean? No LEDs flash? Just one? One or both on all the time?


Nothing happens.  No flash, no nothin.

any other ideas?  Maybe the diagram is wrong?
Accelerate to 88 miles per hour.

nickgammon

How could it be wrong if I just got it to work?

Maybe post a clear photo.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

funkyguy4000

What?! Really?  Maybe I'm not as good a breadboarder as I thought I was.
I should point out that I don't have a bi-color led like the thing says, so I'm just using two leds set up like the diagram.

This is the best picture I can get. 
Accelerate to 88 miles per hour.

nickgammon


I should point out that I don't have a bi-color led like the thing says, so I'm just using two leds set up like the diagram.


That's what I had.

It looks to me like you have something connected to pin 5, which is NC on the diagram.

Is that 10 uF cap in the right way? It looks not, from the photo.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

funkyguy4000

Hmm don't know how that wire got there.
After I removed it, I switched the cap around.  Still doesn't work.
Accelerate to 88 miles per hour.

nickgammon

This is my setup, which works:


Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

funkyguy4000

Hmm, well now I have it working! I'll look over the diagram to see what I did wrong.  Thanks a bunch!
Accelerate to 88 miles per hour.

funkyguy4000

Interesting....
When I connect up the 2nd led in the backwards direction with the resistor going to GND. the whole circuit turns off. I thought that those two resistors might just be shorting out the whole circuit.

Is that whats going on?
Accelerate to 88 miles per hour.

silverxxx

the led is probably shorted out.

nickgammon

http://electronics.stackexchange.com/questions/22291/why-exactly-cant-a-single-resistor-be-used-for-many-parallel-leds
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

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