I produced the magic smoke. :(

Status
Not open for further replies.
Okay, I dug out my copy and posted the page. Check your wiring again. The only thing i can see might be in the upper right corner, where the lines from pin 4 and pin 3 cross... They aren't connected, but putting 12 volt through the output (pin 3) would cause smoke as you described. What voltage relay are you using, coil impedience? Too big could cause some heat.
 

Attachments

  • 555.png
    382.5 KB · Views: 158
Thats the one. I was using a 9v battery with a 9v relay (coil) Then I tried a 12v battery. I may have shorted out pin 3, I dont know. I am going to redo it but without the relay and see what I get.

I guess I could have taken a pic with my digital camera then posted it, forgot abou that.
 
Yeah a picture is worth a hundred post. I breadboard most circuits first, my biggest wiring fault is being off by one hole. I general test the output with an LED to verify the 555 is working right, then move on to the next section. The output of the 555 will be a couple of volts lower than the supply, so use the 9v relay with the 12 volt supply, or use a transistor driver.

I built most of the circuits in the book as a kid, they all work (eventually...). It's usually something simple. Good luck.
 
Status
Not open for further replies.
Cookies are required to use this site. You must accept them to continue using the site. Learn more…