Computer Power supply strange 5V and strange behaviour Teensy is connected

[kurt-olsson]

Took Kyles advice. Keep it simple, 5V only.
Panel works when not in contact with each other. When contact appeares the one backlight goes black.

Made a small video to illustrate this.
https://youtu.be/EIfHY1n3goI

[paulnd]

Are these connected directly to 5v or still through a ULN2803A?

Took Kyles advice. Keep it simple, 5V only.
Panel works when not in contact with each other. When contact appeares the one backlight goes black.

Made a small video to illustrate this.
https://youtu.be/EIfHY1n3goI

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[kurt-olsson]

They are both connected through the ULN2803A.

[iwik]

Kurt,
Have you tried floating the board in the unit that the lights cutout?No possible physical
connection from your pcb to chassis.
Les

[kurt-olsson]

Great tip Les, i will try it right now.

[kurt-olsson]

I give up...

One i released the PCB and got it floating it burned out my Teensy again.
The problem is that i mounted the PCB to a metal backplate and it MUST be the problem.

The one that works is made out of acrylic and has no conttact with the PCB.

Great... 10h of work down the toilet again...

[kurt-olsson]

The bad thing is that this only happened becuase of stupidity!
I drilled a hole through my PCB and attached a metal screw to it and it was connected to a metal backplate.
My brain must have had a shortcircuit when i did that.

It means that those rails on the PCB is connected to eachother...

And the best part it that i soldered my Teensy direct on the board, i did this on purpose because i want things to be tight and not come loose.

But if i hadnt i could just have fixed the PCB and isolated the connections and replaced the Teensy. 30 min job instead of rebuilding the whole PCB...

Well well... at least i learned something today =)

[archen]

It's easy to desolder. Get one of these.. cheap to buy

Should be available at Kjell I guess.


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[kurt-olsson]

I think i have one of those, but didnt think it would work, but now i will give it a try at least

[archen]

Do that. It's easy just heat it enough and put the tool over the solder and fire it off . Just remember to do it fast. The best way is to heat the solder on one side and pump on other and fire it off when you still heat it. Don't know if that's possible for you.

Also if you have some copperstrip (kopparfläta). That will suck it up.

https://youtu.be/Z38WsZFmq8E

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[kurt-olsson]

Lesson learned, PCB in the making. =)

[kurt-olsson]

Ok, here is the answer. Sorry for all the spamming.

Panel 1, i connected +5V to PSU 5V+, GRN to GRN
Panel 2 i connected GRD to PSU 5V+, GRN to 5V+
Panel 3 same as Panel 1.

This is why some panels only worked together and the shortcircuit happened.

I need to check exactly what i decide to be +5V on each panel and do the same on all. Otherwise: TROUBLE.

[iwik]

Kurt,
This is what i use these days to build simple pcb's like you are doing. It's cheap but you cant
make the mistakes you have done. It's a bit more work but as you have to join up the dots.
I found with vero board(expensive) you can leave slithers of copper, some times very hard
to see. Many times i have made mistakes by leaving strips of copper in where i shouldn't.
https://www.ebay.com/itm/5-PCS-10cm-x-10cm-FR-4-One-Side-Prototype-Universal-PCB-Print-Circuit-Board-DIY/231279720694?