Need help with alarm project. Please

[swilus]

I'm trying to get a 555timer to trigger a NC relay for a specific time

Here is my attempt at bread boarding the circuit from the book:


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What happens is that my LED will blink only when I push in the momentary push button & will go out as soon as I let go. It is supposed to stay lit for a small period of time.


Can anyone see a mistake?

Here are a few things I know to be true:
The voltage the book say to use is 9votls. I think right now my transformer is putting out about 14-15

Also, the other thing that I did differently was use a .22 uf ELECTROLYTIC capacitor for C5 instead of a .1uf ceramic capacitor like it speced.

Would any of this be the cause of my problem?

 

[(*steve*)]

Can you show us the circuit diagram you're working from?

Can you measure the DC voltage applied to the 555? (the max allowed is 18V)

Is the "transformer" giving you a nice filtered DC, rectified DC, or even AC? (either of the latter 2 are bad)

 

[swilus]

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I'm not sure what it puts out in that respect

It does put out 15VDC at 420MA

Maybe I need to purchase a desktop power supply?

 

[(*steve*)]

Do they have a circuit diagram in that book?

You can use your multimeter on a volts range to check the output voltage. It may be significantly higher than what is shown on the label.

If you don't have a multimeter, get one. It is probably the most useful tool you'll ever buy.

It looks like you have connected some of your components to the wrong strip on the right of the breadboard. Notice that R6 and C3 need to go all the way over to the far right. You have them plugged in one hole to the left.
I haven't checked everything else, but this seems like a major problem.

You also seem to be using wires wrapped around the terminals of switches etc. This is very hit and miss and make may make things operate eratically too.

 

[swilus]

Thank you

First of all, thank you very much for your time and help and expertise!

I thought that the two bars on the left were connected and the two on there right were connected!!! Silly me! What a big/dumb mistake. Thank you!!

I do own a multimeter and agree with you completely. I work as a water/waste water pump technician and I use multiple meters every day!

My goal is to use this circuit to disengage a normally closed relay for one minute. I need to choose the proper resistor/capacitor combination of course.

Changes made:
Used 9V Batter w/ clip as power supply instead
Cleaned it up somewhat
Soldered connections to my momentary push button

Here is what is going on now, when I press the momentary push button, the LED glows but does not go off!

To me it looks like I have matched the schematic. However, the schematic specs. a .1UF CERAMIC capacitor for C4...... I do not have one so I used a .22UF Electrolytic capacitor. Would this cause the LED to stay lit? Will his cause a problem.




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[swilus]

VICTORY!!!!! LOL I know this is such a stupid easy circuit but I have spent hours on it! But its been a good learning experience. My 555 timer had been abused too much! I swapped it out and it now works!

Thank you for your help! I will try and post a picture of my completed project!

 

[Sparks_21]

glad you got it working,

I made one of these circuits to stay on for 20 minutes and then go off, worked well too