fried my arduinoBT...

so i think I fried my arduinoBT.. :'( im still a n00b when it comes to electricity.

I plugged in a PING))) and a servo s03n all straight up, not paying attention :( I loaded up the program and the nex tthing I see is the ping led lighting up and smoke coming out of the 5v pin!!! dang it, im so pissed off with myself.

well I was reading up tryin to figure out why. The only thing I could come up was, the servo is a 100mA and the ping 30mA. Arduino only give me 50mA right? so I needed a resistor for the ping, and I guess an external power supply for the servo?

I don't get it just the day before I had two servos(same kind) plugged in and everything seemed fine. i need to study some more on resistors and transistors and what not.

I hooked up the batteries and the 3v3 led light up, altho the led was blinkin poorly, I then checked with a multimeter if there was any volts coming out and there was. Is there a way to check to see if the board is completly fired? I tried to pair it with my machine again, but I couldn't see the bluetooth. help! :'( :'(

Did the same with mine a while ago. But it went BANG then sparks flew out along with a trail of blue smoke .. very exciting!

Once there's smoke a few people here suggested there wasn't an easy way to fix it. So I bought another one = )

Arduino only give me 50mA right?

Wrong only 40mA, have you tried the other output pins?

humm. I tried output pin 6, seems dead... however, I 'm not sure I understand. I thought the other output pins wouldn't output anything unless they are programmed too do so.

Also, how do you know it outputs 40mA, is that something you can figure out by the schematic? The reason why I said 50mA is because thats what the duemilanove lists for the 3.3v power on the hardware page http://arduino.cc/en/Main/ArduinoBoardDuemilanove

I can't seem to find the specs of the arduinoBT anywhere, and I really don't know how to read schematics that well.

Check the data sheet for the ATmega168 (doc2545.pdf) from :

http://www.atmel.com/dyn/products/product_card.asp?PN=ATmega168

On page 302 in the section “Absolute Maximum Ratings” it says:

“DC Current per I/O Pin … 40.0 mA”

This is saying don’t try and draw more than 40mA continously from a single ouput pin without risking damage to the device.

Also note the line in the same section:

“DC Current VCC and GND Pins… 200.0 mA”

This says that the total current drawn by the ATmega168 AND the current drawn by all the things directly drawing current from it must add up to less than 200mA DC. So directly connecting 10 LEDs all drawing 20mA to the ATmega168 is pushing the limits of what you can expect it to handle without failing!

The graphs on pages 326 under section “27.8 Pin Driver Strength” show how the output voltage changes with current for sourcing and sinking current for different power supply voltages, which is also an important consideration in many applications. You can see that as the current goes up, the voltage goes down, which can effect the performance of many circuits.

Note that these graphs show much higher currents than 40mA but remember that 40mA is the maximum DC current, ie maximum continuous, it can and will momentarity go higher than 40mA when a signal is switching.

In general, you need too use a more rugged buffer device connected to the output from the Arduino to control devices that source or sink more than 20mA or so to be on the safe side.

The 3.3V 50mA max you’re talking about I think is for current drawn from the internal 3.3V regulator in the FT232RL USB <-> serial interface IC, it has nothing to do with the ATmega168.

I 'm not sure I understand. I thought the other output pins wouldn't output anything unless they are programmed too do so.

Precisely so program up a blinky sketch to make them do something and see if it does. There is no point in replacing the processor if you can shuffle the pins it uses and avoid the one you destroyed.

Grumpy_Mike:

I tried to pair it with my machine again, but I couldn't see the bluetooth.

thats not possible, my machine can't see the device anymore... its pretty much dead, but current goes through it, maybe its just the processor what got fried... can I salvage parts? like the bluetooth module?

letaage: Thanks for the link and your detailed explanation, that really helps out understanding what really happened. I was still a bit puzzled.

I know that but if you connect a serial lead from a USB to TTL serial board to connector JP2 you can program it just like a conventional board. In that way it can still be of use. You would then have to hack the Blue tooth software to use a working pin.

ohhh ok. I see I see, well, im defiantly going to try that! I'll let you know what happens.