Arduino Forum

Using Arduino => General Electronics => Topic started by: funkyguy4000 on Mar 05, 2013, 03:33 am

Title: 555 timer beginner circuit help
Post by: funkyguy4000 on Mar 05, 2013, 03:33 am
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 (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?
Title: Re: 555 timer beginner circuit help
Post by: TeslaIaint on Mar 05, 2013, 03:42 am
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.
Title: Re: 555 timer beginner circuit help
Post by: funkyguy4000 on Mar 05, 2013, 03:48 am
Yup, everything has been tried with new parts, even the power supply
Title: Re: 555 timer beginner circuit help
Post by: cmiyc on Mar 05, 2013, 04:40 am
Make sure the 33K is connected to output, not 9V.
Title: Re: 555 timer beginner circuit help
Post by: nickgammon on Mar 05, 2013, 04:54 am
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?
Title: Re: 555 timer beginner circuit help
Post by: funkyguy4000 on Mar 05, 2013, 05:06 am

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?
Title: Re: 555 timer beginner circuit help
Post by: nickgammon on Mar 05, 2013, 05:26 am
How could it be wrong if I just got it to work?

Maybe post a clear photo.
Title: Re: 555 timer beginner circuit help
Post by: funkyguy4000 on Mar 05, 2013, 05:52 am
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. 

Title: Re: 555 timer beginner circuit help
Post by: nickgammon on Mar 05, 2013, 05:59 am

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.
Title: Re: 555 timer beginner circuit help
Post by: funkyguy4000 on Mar 05, 2013, 06:04 am
Hmm don't know how that wire got there.
After I removed it, I switched the cap around.  Still doesn't work.
Title: Re: 555 timer beginner circuit help
Post by: nickgammon on Mar 05, 2013, 06:17 am
This is my setup, which works:


Title: Re: 555 timer beginner circuit help
Post by: funkyguy4000 on Mar 05, 2013, 06:41 am
Hmm, well now I have it working! I'll look over the diagram to see what I did wrong.  Thanks a bunch!
Title: Re: 555 timer beginner circuit help
Post by: funkyguy4000 on Mar 05, 2013, 06:43 am
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?
Title: Re: 555 timer beginner circuit help
Post by: silverxxx on Mar 05, 2013, 10:32 pm
the led is probably shorted out.
Title: Re: 555 timer beginner circuit help
Post by: nickgammon on Mar 05, 2013, 10:36 pm
http://electronics.stackexchange.com/questions/22291/why-exactly-cant-a-single-resistor-be-used-for-many-parallel-leds
Title: Re: 555 timer beginner circuit help
Post by: afremont on Mar 05, 2013, 10:46 pm

http://electronics.stackexchange.com/questions/22291/why-exactly-cant-a-single-resistor-be-used-for-many-parallel-leds



This is a little different situation isn't it?  The LEDs might be in parallel, but they are never on at the same time since they are reversed, so this wouldn't apply, right?
Title: Re: 555 timer beginner circuit help
Post by: nickgammon on Mar 05, 2013, 10:49 pm

When I connect up the 2nd led in the backwards direction  ...


I assumed he meant he flipped one of the two LEDs so now they are both in parallel.
Title: Re: 555 timer beginner circuit help
Post by: EVP on Mar 05, 2013, 10:50 pm
So with a 5v supply maybe 12 at a push what is the best way to power 256 ir led's? all with the same signal a pwm signal. After much head scratching and taking apart a 60 led torch to find all led in parallel and one resistor, i decided on a constant currant led driver and to put them in groups of around 700ma(what the driver is rated at). Now the led are rated at 20ma maybe more for pulsing, i have them running at around 10ma. My thought was an i think i'm wrong now was that at that currant there would be no heating and no thermal runaway.

How else could i  power them?
Title: Re: 555 timer beginner circuit help
Post by: nickgammon on Mar 05, 2013, 10:53 pm

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?


If you moved the top 220R resistor to go to Gnd, then there is no power reaching pins 2 and 6.