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Topic: Help with circuit - why does this work? (Read 1 time) previous topic - next topic

gpsmikey

Yes, you may have let the magic smoke out :-)  A chip like that getting "really hot" is not a good sign.
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3

JimboZA

I must have screwed up something with my nano...
The ATmega chip got really hot for a while.  Now my arduino IDE doesn't see the board at all.  Maybe I shorted something on it.  This is quite the frustrating experience.
You need to change the thread title to "why DID this work".... :)

The frustration is all part of the fun.
Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)
Dr Perry Cox: "Help me to help you, help me to help you...."
Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

TomGeorge

Hi,
When you added the LED did you use a series current limit resistor?

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

shmish

#18
Feb 20, 2016, 06:06 pm Last Edit: Feb 20, 2016, 07:17 pm by bcphysics
Hi,
When you added the LED did you use a series current limit resistor?

Tom... :)
Yes I used a 150 Ohm resistor on each LED.
I also soldered a lead to the Vin on the arduino for a 9V battery strap. I'm guessing that I may have added too much solder and that it shorted with the gnd pin on the arduino. I checked connectivity between the two pins before powering up (they weren't  electrically connected) but maybe it was intermittent.  I don't know why this would cook the arduino though.

I'll pull out the arduino and put in a new nano.
What tests can I do with the multimeter to see that things are connected the way they are supposed to be connected?  With the soldered board, measuring current isn't going to happen so I'll I can do is check resistance and voltage. I think what I really want to measure is the current feeding into the base of the transistors though. Maybe I should de-solder these as well and measure current there?

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