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Brake light flasher (555 - based) circuit works on breadboard, but not PCB

bob monsen

Jan 18, 2010
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Pull the 555 and Q1 from both the working breadboard, and the circuit board. Now, power both circuits, and compare the voltages at the same 555 pins on both circuits. I looked at your board, and although it is hard to tell, it looks like there isn't power to the 555. Can you upload the schematic from the pcb software you used to make it?
 

domiflichi

Jun 15, 2016
10
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First off, I want to say I'm sorry for the long delay - I didn't want you guys to think that I didn't appreciate all your help. I just wasn't able to work on this project for a while. But, I finally did yesterday. I appreciate everyone's replies so I thank you for that. I wish I had half the knowledge/experience you all have individually. Honestly, a lot of things you guys were saying went over my head. Thankfully, one of the first and easier things to check ended up being the culprit!

What was it?

R1 and R2 weren't connected on the PCB as they should have been! One of the images below show the little jumper wire I used (came from an individual wire of a CatV cable) to fix it. The other image shows (on a different PCB that I just soldered all the parts on it yesterday) how I just connected the 2 resistor's leads when I was soldering the components on.

If there is something wrong with the way I did the 'fix', by all means, let me know. I don't know what's best practice or bad practice.

So I tried testing for continuity on my 2 remaining unpopulated PCBs (before I soldered up the 2nd one) and there was no continuity between R1 and R2. I'm not sure where that connection between R1 and R2 was lost/messed up because obviously his schematic is correct.

The Fritzing files are linked to on his site, but here's the direct links to them here since 'bob monsen' requested it:
http://www.dudley.nu/projects/brake_light_blinker/brake_blinker_1.fzz ('design' file)
http://www.dudley.nu/projects/brake_light_blinker/brake_blinker_1.zip (board files)

Again, thank you everyone so much! And I have to give [73's de Edd] an extra thank you since his post was the one that directly helped me to solve/fix it.
 

Attachments

  • Jumper wire between R1 and R2 Fix - 1 (cropped).jpg
    Jumper wire between R1 and R2 Fix - 1 (cropped).jpg
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  • Bottom of PCB with R1-R2 jumped - 1 (cropped, resized).jpg
    Bottom of PCB with R1-R2 jumped - 1 (cropped, resized).jpg
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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With the information you've given us, I think I can make out a break in the track.

bare-pcb-top-1-jpg.33218


It might just be a trick of the light, but is the trace which goes along the area outlined as R1 broken?

It might be worth looking at the circuit board layout and making sure the track didn't become broken in it.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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I just installed fritzing. The layout appears correct.
 

Audioguru

Sep 24, 2016
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I think they painted the board almost black so that you cannot see their mistakes and so that they can use white text.
I have never seen a pcb before that does not have its tracks very visible.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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I have never seen a pcb before that does not have its tracks very visible.

Plenty of people do it. It's "trendy".

So then the board house, Osh Park is at fault then, right?

Possibly, but it could also be a software issue in fritzing.

It would at least be useful to email them and enquire.
 

domiflichi

Jun 15, 2016
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Jun 15, 2016
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I contacted OSH Park about the boards, and they emailed me back with an image (see attached)

Looks like it's on this end - there is a clearly 'broken' trace. How does that happen - a bug in the software as [*steve*] mentioned? And then I had a question - in one of the images I circled in blue an 'island'...I was wondering what that is and why it's there.

In a way, I'm glad to know that it's not OSH Park because I may like to use them in the future.

Thanks again everyone for helping out this newbie! I really appreciate it and may never have figured it out on my own!
 

Attachments

  • PCB Board trace emailed from OSH Park floating island marked.png
    PCB Board trace emailed from OSH Park floating island marked.png
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  • PCB Board trace emailed from OSH Park.png
    PCB Board trace emailed from OSH Park.png
    48.9 KB · Views: 57

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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How does that happen

It's a thing that I'd raise on a forum dedicated to fritzing. The trace doesn't look like that in the layout you uploaded.

in one of the images I circled in blue an 'island'...I was wondering what that is and why it's there

It is part of the filling of empty space with a ground plane. often these are stitched together, even if they're not, it's no great issue in most cases. If you were etching your own boards it would minimise the amount of copper that needs to be etched, making your chemicals last longer.
 

73's de Edd

Aug 21, 2015
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Sir domiflichi . . . . .

You ended up with a faulty board in the respect of not knowing . . . . that what should have been a closed circuit was ending up with a gap . . .yet with two rounded ends creating that gap.
THEN this is all being hidden under DARK, resist so that one would not even know that the situation existed.

Rather than the old ugly wire, try the pulling of the resistor covering this area and then micro-scrape off the resist to expose what I have shown and then form a Cu jumper and solder tack and then solder reflow the joints to cover all . . . . and then replace the resistor.

Howtodoittoit . . . . .


Opne Ckt 555 Board.png


73's de Edd

.
 
Last edited:

domiflichi

Jun 15, 2016
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Oh ok. Yeah maybe I will (start a thread @ the Fritzing forums).

That makes sense about the grounding plane.

Thank you for the more elegant way to fix the board, 73's de Edd. It kind of went over my head a little - I don't know what a Cu jumper or solder tack is. I'll have to look that stuff up. ;)
 
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