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Here is a simple example of what been happening to various pcbs when I play with them. I have an arduino powered by USB. Then a 5V and GND connected to a logic level shifter's HIGH and GND respectively. The VCC of the shifter is smoking and is hot. I cant understand why this is happening. I looked at the solder and it looks ok from the top and bottom of the pin. The board seems to work once the rest of the wires are connected. I stopped using it when I saw the smoke as I don't know where to go from here. What am i doing wrong?

https://www.sparkfun.com/products/12009 is the PCB of the shifter.

EDIT: added schematic from the fritzng EDIT: The intent was to drop the 5V IO to 3.3V to talk to a ESP8266. I didn't get that far when I saw the smoke.

enter image description here

enter image description here

example of simple device smoking

Circuit diagram of the level shifter:

enter image description here

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    \$\begingroup\$ I see smoke. whatever is on that small board doesn't like the 5V connected to those terminals. \$\endgroup\$ – Jasen Oct 4 '18 at 10:30
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    \$\begingroup\$ Could you update it with a proper schematic? Fritzing drawings aren't usually very well received as they are messy and quite frankly, they are not an engineering drawing. As engineers, we prefer to read proper schematics. Could you also state what it is you are trying to do, and what it is you are expecting? I see you have nothing connected to Lv, so what level are you actually trying to shift a voltage to? And what signals are you trying to shift? It's not complete. \$\endgroup\$ – MCG Oct 4 '18 at 11:05
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    \$\begingroup\$ Curious ... it appears that the smoke is originating directly from the pins, not from a component on the board. Did you assemble this board yourself? It would seem that there's a short circuit of some sort directly between HV and GND. \$\endgroup\$ – Dave Tweed Oct 4 '18 at 11:45
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    \$\begingroup\$ I think the question now contains everything necessary to answer it. It's still puzzling though. \$\endgroup\$ – pipe Oct 4 '18 at 11:47
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    \$\begingroup\$ Bizarre. Ground plays no part in the circuit - none of the components on the level shifter should have any connection to ground at all. Ground is only there to bind the grounds of the low and high voltage sections. There shouldn't be anything capable of shorting HV and ground. \$\endgroup\$ – JRE Oct 4 '18 at 11:54
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If your circuit is connected the way it is shown in the schematics, then there really shouldn't be any reason why it is emitting smoke. That is very strange. The first thing you should do is remove the leads supplying the power and check the board for shorts. If you can't find any, the to be safe, check your Arduino board by using it with something else, and make sure it is still working. Also, try moving the level shifter PCB to a different part of the breadboard, just to be safe as there could well be a problem there. Breadboards aren't 100% reliable.

If the Arduino is working, and you have found no shorts on the level shift PCB, and the same thing happens elsewhere on the breadboard, then the only thing I can think of is you have a broken board and you will need to get a replacement. Not entirely sure what would fail to make it smoke like that, but that would be the only thing left.

To be sure, you could always supply the board with a different 5V source, perhaps a 9V battery with a 7805, or if you have a power supply, then just put that straight on there too and see if it starts smoking.

It'll be a process of elimination between the 3 components you have: Arduino, Breadboard, Level shift PCB. Chances are you have a faulty Level shift PCB. It happens sometimes unfortunately.

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  • \$\begingroup\$ Note that a faulty level shift board would have to mechanically faulty. There are no components apart from the PCB itself and plastic tie bar of the headers which are in any way connected to both rails. \$\endgroup\$ – Chris Stratton Oct 4 '18 at 17:22

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