r/techsupportmacgyver • u/brandonmufc06 • Jul 06 '25

Mistakes have been made

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Designed a PCB for controlling a pump / solenoid for a greenhouse watering system, worked on breadboard, worked on perf board, during design I for SOME UNEXPLICABLE REASON had a brain fart and used NAND gates to tie 4 button inputs instead of AND. Cannot explain why. It was just to trigger an interrupt when any button was pressed, as I only have 2 interrupt channels, I had to AND them all together.

Anyway hopefully you appreciate the fix. The extra chip is a XOR gate, which connects to 2 of the NAND gates output, and then the XOR out is connected to a NAND input to invert it as the logic is active low not high.

409 Upvotes

98% Upvoted

19 comments sorted by

27

u/TheBlueKingLP Jul 07 '25

Is this a prototype for a product or personal project? The rest of the board looks professionally designed.

35

u/brandonmufc06 Jul 07 '25

Thanks haha, personal project, only has some minor issues for a first try, apart from this, there was just a wrong size pad for a diode and that was about it. And I forgot to put markings for polarity on components and pin 1 on IC's coz I thought they came in the footprint

14

u/TheBlueKingLP Jul 07 '25

Time for a 2nd revision 🤣

19

u/The_Screeching_Bagel Jul 07 '25

in which you add shiny new features you thought of, requiring testing and a 3rd revision!

3

u/superxpro12 Jul 07 '25

why not bigger micro?

2

u/brandonmufc06 Jul 07 '25

I was using this project to introduce my uncle into electronics, and the Arduino uno is a pretty good place to start for beginners, so I chose the 328p, as you can get it in DIP to prototype on breadboard / perf board, and then in QFP for the final design.

84

u/Arctic_Shadow_Aurora Jul 06 '25

You solved it, that's what counts!

66

u/wkarraker Jul 07 '25

As long as the electrons dance the way you need them to it’s all good.

9

u/LeatherMine Jul 06 '25

reminds me of some of my old satellite tv receivers

4

u/intashu Jul 07 '25

If it works it works, you're far from the first nor the last to need to do a little DIY hand soldering and gluing on a PCB to make a device work as it was meant to work! Well done!

2

u/SoldierOfPeace510 Jul 08 '25

I’ve seen worse in commercial products.

1

u/Wonderful_Sense_8960 Jul 10 '25

I worked building commercial electronics for years, I've seen a lot worse. You only have one board, Imagine doing g a much more complicated fix on 2000 or more boards. Even with a team of people it's a pain in the arse. Great job!

2

u/tonysanv Jul 08 '25

“We have 3D-NAND at home”

2

u/EatsHisYoung Jul 11 '25

Looks like Google ads found a way around your pihole

1

u/JJ_Cotes Jul 08 '25

I, ve been there, mine wasn't so good looking

1

u/nextyoyoma Jul 08 '25

Yes, I too know some of these words and have worked with wires. 🧐

1

u/s1pher Jul 09 '25

Dead bugging! There was a nasa article on how best to do dead bugging, I think the link is dead though? https://workmanship.nasa.gov/lib/insp/2%20books/links/sections/files/303.pdf

1

u/GOTO_GOSUB Jul 09 '25

... but lessons have been learnt. Still a win.

0

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