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Challenge: find twelve design faults

gophert

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Most Helpful Member
Each element in the circuit is labelled ( c1, c2...) There are twelve design faults can you find them ?
Q2 i one of them

Yup, I count 12 design issues. Not exactly a "challenge" (boarderline stupid).
 

dknguyen

Well-Known Member
Most Helpful Member
I found 14, but that might be because of whether you count something as a single error or two separate errors. The 13th thing was a little bit ambiguous due to lack of info about where the connector was going, or maybe because I don't trust internal pull-ups.
 

schmitt trigger

Well-Known Member
In addition to the naive mistakes like inverted caps and diodes, why would anyone use a 144 pin microcontroller if all you are going to use is about a dozen ports? What a waste.
 

dknguyen

Well-Known Member
Most Helpful Member
In addition to the naive mistakes like inverted caps and diodes, why would anyone use a 144 pin microcontroller if all you are going to use is about a dozen ports? What a waste.
Maybe they have code and PCB layout from somewhere else and don't want to redesign?
 

schmitt trigger

Well-Known Member
In other words, they are lazy enough to just copy and paste from other design, and insert some silly mistakes while doing so.
 

MrAl

Well-Known Member
Most Helpful Member
Hi,

I didnt even look at the schematic yet, if that is what that is, all i had to do was read the other replies and i can see that there is only one mistake:
They hired the wrong guy for the job :)
:)
 

gophert

Well-Known Member
Most Helpful Member
Hi,

I didnt even look at the schematic yet, if that is what that is, all i had to do was read the other replies and i can see that there is only one mistake:
They hired the wrong guy for the job :)
:)
I'm thinking he ask us to do his homework so he could spend more time at the pub. Or, he already spent too much time at the pub and NEEDED us To get it done for him.
 

Beau Schwabe

Active Member
I didn't think this was asking for help.... it sounded more like a "Golf Challenge" or puzzle you already had an answer to. I found 36 issues, but could probably find more if I looked harder.
 

Beau Schwabe

Active Member
Here is the schematic with the 36 potential problems... dots indicate nodes that are not connected in the schematic or wrong connections. Lines indicate a wrong component ... i.e wrong kind of MOSFET, backwards MOSFET, wrong schematic symbol, wrong diode direction, resistor value too low (EEPROM)
 

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dknguyen

Well-Known Member
Most Helpful Member
Yeah I think you found the oscillator issue though I don't entirely agree.

I thought it looked funny the first time I saw it but am not good with oscillators. I think C32 and C33 shouldn't be there. I think C28 AND C29 are required though. I also think the oscillator itself is completley wrong too...pins 1 and 3 should be going to the MCU. But maybe there is more than one way to wire an crystal to an MCU. I wouldn't know.
 
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Beau Schwabe

Active Member
C28 and C29 are required but they are too small .... 18pF is typical, however look at the datasheet on that oscillator part, it might have the proper caps built in. (Don't know didn't look myself). If so, then he wouldn't need any caps there. The two pins on the oscillator I have dots on should be swapped. C32 and C33 should be removed. It is nit picky I know, but there are several nodes left unconnected... if left to an auto router, the connections would not be made. That is the main significance there.
 

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