A puzzling 555 strobe question

chiver · Post by **chiver** » Wed Apr 02, 2014 9:46 pm

I built a 555strobe circuit, it's not the prettiest. By that I mean it's not on a PCB, I do not have the means nor the skill to design and make one. How ever using a slot made to fit a 555 chip. I soldered everything together. Tested it and it worked. Now that was a few months ago, I wired it up again to a 9volt 200MA wall wort and it didn't flash, as I looked around it to see if anything touching the chip started to burn. I changed the chip and still no flash. I tried it on a 9v batt, which it was tested on, and no flash and the chip still started to burn.....any ideas?

Bellerophon · Post by **Bellerophon** » Wed Apr 02, 2014 10:10 pm

For starters, when it worked, was a wall wart supplying the power, or a 9V battery? Timer chip circuits often don't work with rectified AC since it will trigger them 60 or 120 times per second.

The chip is overheating now? Then too much current is being drawn though it. Your mission, should you choose to accept it, is to find out why. Sorry man, couldn't resist.

Maybe post a circuit diagram for us to look at. Check all those resistors and capacitors, too.

chiver · Post by **chiver** » Wed Apr 02, 2014 11:02 pm

When I tested it, it was from a 9v bat. But when I put it on a 9v now it still cooks. Even with a new chip

Bellerophon · Post by **Bellerophon** » Wed Apr 02, 2014 11:14 pm

Something else in the circuit is causing the chip to draw too much current. Perhaps something happened when connected to the wall wart, but that's just speculation. My execrable soldering skills are often my only guess why when my circuits don't work.

Mr. Engineer · Post by **Mr. Engineer** » Tue May 06, 2014 7:25 pm

There is a very strong possibility that there is a short.

Please upload a nice clear macro photo for us to have a look.

b5ranger99 · Post by **b5ranger99** » Wed May 07, 2014 10:57 pm

It is entirely possible the wall wort was not supplying clean power.
This could have caused damage to other components.
That might explain why the 555s keep frying.

chiver · Post by **chiver** » Thu May 08, 2014 11:09 am

Granted it's not the cleanest, but nothing is touching that shouldn't be, if it's not saldered it's not touching. I dot have the means or know know how to make a PCB. Like I said it was tested when I first made it, it was tested with a 9v batt, and it worked fine, no heating either, not there is no flash and chip over heats

http://i1170.photobucket.com/albums/r52 ... sfnpwj.jpg

http://i1170.photobucket.com/albums/r52 ... lftvfr.jpg

Bellerophon · Post by **Bellerophon** » Fri May 09, 2014 9:04 am

Pop the chip out of the socket and check the capacitors and diode with your meter. One of them may be fried. If everything is okay, you could try it again with a different 555 chip in the socket--worst case, you end up with 2 dead timer chips. Test it with a 9V battery first.

If you can't find the fault, the components are all cheap, so make another one.

Before you try to power it with the wall wart though, check its DC and AC voltage. If the meter reads both, the wall wart is putting out rectified AC, which can override the circuit you built to trigger the chip at a controlled rate. A big enough cap across the wall wart's output will smooth the AC component enough so it looks like DC.

I'm not set up to make PCBs either, so I use perfboard with wires in place of the traces. Like you did, I always use DIP sockets so I don't overheat ICs.