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Topic: 12-14v from motorcycle... @ Vin (Read 1 time) previous topic - next topic


Apr 20, 2013, 04:43 pm Last Edit: Apr 20, 2013, 04:59 pm by pcguru000 Reason: 1
So I hooked up my project for a quick test of the display to my bikes power- worked great for a 20 second test (just running through the numbers on my 7-seg display) .

Was happy with the results so I unplugged it all and went inside. Go to plug my arduino into the computer- nothing. power led is on, green usb led is, and yellow tx led is on- all just solid... but nothing happens... computer doesn't see it at all.

I pick it up to see if the plug is not seated well- and HOLY crap the 32u4 is scorching hot...

What happened? Is this toast?

EDIT- im only posting this because the spec says the limit is 20 volts-


I am 99% positive that i didn't even exceed 12.5volts- i never had the bike even turned on (When i know it throws 14.1 or so) - and if i did exceed 12 volts- it wasn't for more than half a minute...

I suppose I just need to invest in some of these https://www.sparkfun.com/products/107 or similar (maybe this http://www.radioshack.com/product/index.jsp?productId=12669026&filterName=Category&numProdsPerPage=60)

I apologize I am total newb at this- feel like I got into this stuff on the wrong angle... i can program but Im really just learning the electrical stuff...


You haven't provided a wiring diagram to show how you connected it to your motorbike so how can we give you any useful advice.

Two or three hours spent thinking and reading documentation solves most programming problems.


As I said- its really simple, just a straight soldered pair of wire (ground, power) to the Vin and Gnd on my board (I have the duino mounted on some female mobo headers so i can pull it off if i want)

The rest of the wiring is just basic LOW or HIGH digital pins, and a 3.3 v line to drive the common anode 7 segment.

It's so brutally simple I cant imagine how it went wrong- i mean it worked perfectly on the bike.

Bike 12v -> Duino Vin
Bike Gnd -> Duino Gnd

Duino 3.3v - > Common Anode 7-Seg
Duino Digital Pins 2-8 -> 7-Seg

Nothing more :/ - worked great before from my PC too. just guessing the 12v from the bike fried it somehow... Does this happen?


I'm guessing you can supply power at up to 20v into the power socket but I'm not sure you can connect 20v to the Vcc pin. My guess is there is a voltage regulator between the power socket and the Vcc pin.

If you did connect 12v to a 5v pin ... well ...

Two or three hours spent thinking and reading documentation solves most programming problems.


I'm surprised the Arduino chip got so hot, it's usually the v.reg chip, eg
(14V-5V)*100mA = 0.9 Watts, and maybe more considering you're driving
7 or more Leds.

Besides going to a "real" v.reg [as opposed to those teensey-weensey smt things],
you might just try using something in series in the Vin line to provide an IR drop.
Eg, a fat resistor or a 5 Watt, 5-8V Zener diode. Either one will get somewhat warm,
but will move the heat off the Arduino board.

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