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Support Forum » big trouble in little china

December 20, 2010
by vespertilio
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Hi there,

I recently posted in another thread looking for help with making a digital music box. I got the impression from the post that I should proceed to make the other projects in the nerd kits guide before I could really sink my teeth into the higher level projects. So I started working on the blinking LED project.

At first when I plugged the battery into the bread board, the LED would blink on for a second. I figured that was a good thing. But when I plugged the board into my computer and ran the make file for the blinking led, it would give me an error that I took to mean it couldn't find the chip. After fiddling about, the LED would stop lighting up when I plugged in the battery. Assuming I had a low battery, I went to the drug store and bought some more 9V batteries. When I plugged in a fresh one, the LED came on! But I got the same error, and after the first attempt I got nothing. I tried switching USB ports too, but that didn't seem to change anything.

Now here's where the problems start: I gave up figuring I'd try again tomorrow. I plugged my mouse and keyboard back into the USB ports and guess what? They didn't work. I figured maybe something was holding them up in the background or something so I rebooted. Guess what? I can't tell if my computer is doing anything, but the screen is completely black, the camera (which it uses for logging in) doesn't light up and I'm pretty concerned my computer just got bricked, not to mention my MCU is probably fried.

What do I do now?

December 21, 2010
by Rick_S
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Hopefully bad things did not happen ... :(

  1. If you still have access to a computer (I assume you do since you posted here) can you take an overhead shot of your troubled circuit and post it here? That would help tremendously.
  2. You didn't have the USB power and Battery power plugged into the board at the same time did you?? That is never a good practice and can make bad things happen.
  3. When you turn on your computer (Laptop or Desktop?? MAC or PC??) do you see anything at all like the initial bios screen. Does the power LED light up? Do fans start? Does the Hard Drive make sounds?? Or is it totally dead.

I'll be honest with you, while I hope you didn't accidentally kill your computer, based on your description it doesn't sound good.

Rick

December 21, 2010
by vespertilio
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Thanks for the response Rick,

  1. I do have a second computer, a macbook air (Which actually got rebooted when I tried working on the circuit with it.) Here are some pictures of my circuit: http://img705.imageshack.us/i/circuitx.jpg/ http://img191.imageshack.us/i/circuit2.jpg/ http://img406.imageshack.us/i/circuit3.jpg/

I would've embedded them here but they turned out to be pretty massive.

2.I did in fact have the USB and battery plugged in at the same time X_X. Was there a warning about that somewhere that I missed? When I constructed the initial project I sort of figured it was a bad idea and didn't do it. But then from reading different posts on the forums here, I kind of got the impression that I was supposed to have them connected if something wasn't working.

  1. It's a PC and I don't get anything. I know it's on because the keyboard lights up(it's an alienware laptop) and the fans turn on. But the screen is pitch black. I have a monitor I plug my laptop into too, which is also black when I boot up my computer.

It's kind of weird I think that this problem didn't manifest til I shut down my computer isn't it? Man, this is so depressing, this computer is barely a month and a half old :(. What should I do about this?

December 21, 2010
by Rick_S
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If the red and black wires on the right side of the 1st picture are the ones going to the 9v battery clip, you wired your battery wrong and sent 9V to your circuit and the USB port on your laptop. That is about the worst scenario you could have. That could have sent 9V through the laptop's 5v rail and at the least blown the USB power on the ports it was connected to. But unfortunately it sounds as though it may have done more.

The ground wire of the 9V battery should go to the ground rail as you have it, but the red wire should go to the input pin of the voltage regulator so it can drop the 9V down to 5V. With the 9V red wire on the rail, it has the effect of connecting the 9v to the output side of the regulator - it probably got quite warm - and that's what most likely killed the battery.

If the laptop is less than 2 months old, is it still under warranty? You might get lucky and get it fixed / replaced under that.

You could try wiring it properly to see if the parts still work -- there is a chance (maybe slim) that they will.

Rick

December 21, 2010
by Rick_S
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And one last thing, NEVER have your battery connected to the circuit when the USB power is in place.

December 21, 2010
by vespertilio
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Ho man, that makes sense but it sounds like I really messed up. That means my chip probably is burned out then eh? Definitely learned a few things from this experience X_x...

Thanks for the help Rick, I'll definitely never attach a battery to a circuit board connected to my computer ever again, and maybe never attach a battery to anything I'm plugging into my computer X_x.

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