EEVblog #17 - I hope your next project DOESN'T work!

I hope your next project DOESN'T work!, dual purpose I/O pins can be a trap, and www.octopart.com
(Sorry about the audio hum, new mic problems)

Category:

Science & Technology

Tags:

• project
• circuit
• micro
• microcontroller
• pic
• blog

[Pentium100MHz]

My last project didn't work at first, so I learned what happens if I leave a CMOS input floating, a signal has too long rise time and why would I need to connect capacitors across rectifier diodes in a FWB if I wanted to use the 50Hz signal from the power transformer (because otherwise I would get a spike and the signal would be detected as 100Hz).

[EEVblog]

@Pentium100MHz Good work. Next try floating the power pin and see what happens!

[etalon3141]

Funnily just after I saw this, my next project didnt work! It was fine on a breadboard, but having digital sensors on the end of 50m of telephone cable meant I got nothing back. The datasheet calls for pullup resisitors between 5v and the data line and I had done this on the circuit board. To fix it, I found I had to add some high value (33kohm) pullups on the end of the 50m data line.

[williefleete]

when i made the second prototype for my 8 digit display, i'd shifted to using a tristate output shift reg for addressing the display registers and i found all the display registers were changing and showing the same outputs, as im using the OE pin on the tristate register it makes the strobe lines on the display registers OC and with noise it was strobing the display registers, putting on some pulldown resistors helped with that

[mariushmedias]

Oh man... i don't know why I've heard findtubes instead of findchips, maybe it's your accent. Don't go to what I mentioned, it's nsfw...

Everything's ok in the end.

[prenvo]

6:15 = a face on the whiteboard. Wonderful.

[heroineworshipper]

Is anything a trap for old players?

[gishidenki]

I once had some serious problems with an Atmel flash IC in a no-lead package that was not fully solderded onto my board. So one (or possibly many) pins were only coupled by capacitance. It drove me freeking nuts finding this fault, as you could not measure the signals at the leads. The flash's basic functions like reading and writing larger data blocks seemed to work without problems but more specific stuff like reading a config register failed. After re-soldering the chip it finally worked.

[GRAHAMAUS]

@BusterBlader910 I'm an ex-electronics engineer - these days I write software. But when I started I designed analogue RF transceivers (private mobile radio systems), then went on to low-power digital RF communications, some consumer electronics design (wireless burglar alarms), then one-off electronics display systems for exhibitions and education, but then drifted into software. If you understand the theory, can build stuff that works in practice, you can do what you like.

[averagemale2000]

love your debug story. nice to know the pros go through the similar bug hunts as us amateurs do, allbeit, your bug hunt involve non-amateur components.