justanoob
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Shortcircuiting...

Sun Nov 17, 2013 10:34 am

So I was doing this assignment for school where I'm supposed to light up a LED and then at first, I got it to work, and then I started unplugging it to try something else out for the next part of the assignment and I kept forgetting to use the poweroff command like I was told. And I think I might've shortcircuited something to the point where no matter where I put the LED, it doesn't turn on anymore. So I was wondering if this is something that I could potentially fix, or if it's permanent damage that'll require me to buy a new breadboard or the actual pi board or both. :(

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DeeJay
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Re: Shortcircuiting...

Sun Nov 17, 2013 12:20 pm

Does the RPi still boot up and run?

Does the LED light up if you connect it, and its protective resistor in series, between Pins 1 (3.3v) and 6 (Ground) of the P1 GPIO header?
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justanoob
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Re: Shortcircuiting...

Sun Nov 17, 2013 12:33 pm

Yeah, it still boots up perfectly and everything runs the way it did before, but it's just that no matter where I move the LED and resistor to, it doesn't even light up anymore like it did earlier. I'm doing the same exact thing as before, and nothing happens to it. But when I make the 3.3v touch the + end of the LED, it resets the pi (and I guess short-circuits it, right) the same way it did earlier when I was trying that out. I hope that doesn't mean that I screwed it up really badly just by doing that a few times.

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DeeJay
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Re: Shortcircuiting...

Sun Nov 17, 2013 2:01 pm

DeeJay wrote:Does the RPi still boot up and run?
Answered that bit - so you haven't 'fried' the whole of your RPi. That's good.

Now try answering this specific question:
Does the LED light up if you connect it, and its protective resistor in series, between Pins 1 (3.3v) and 6 (Ground) of the P1 GPIO header?
And yes, if you make what is effectively a short-ciruit between the 3.3v pi and ground nearly all the current available from the power supply flows through that path not leaving enough to run the processor, so it shuts down.
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klricks
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Re: Shortcircuiting...

Sun Nov 17, 2013 2:28 pm

Remember an LED has polarity, it won't work if turned the wrong way around.

If you connect a standard LED to power and ground without the proper resistor, even for a second, then the LED will be destroyed.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

justanoob
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Re: Shortcircuiting...

Sun Nov 17, 2013 5:45 pm

DeeJay wrote: Now try answering this specific question:
Does the LED light up if you connect it, and its protective resistor in series, between Pins 1 (3.3v) and 6 (Ground) of the P1 GPIO header?
And yes, if you make what is effectively a short-ciruit between the 3.3v pi and ground nearly all the current available from the power supply flows through that path not leaving enough to run the processor, so it shuts down.
So I guess the answer to that question is no, since I connected the resistor with it and it still couldn't light up. So is there anything I can really do about this? Like what part(s) do I have to replace?

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DeeJay
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Re: Shortcircuiting...

Sun Nov 17, 2013 6:10 pm

Try just replacing the LED as a first step.
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justanoob
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Re: Shortcircuiting...

Sun Nov 17, 2013 7:13 pm

DeeJay wrote:Try just replacing the LED as a first step.
Sadly I've just tried replacing the LED again and it didn't do anything. Now that I think about it, I might've short-circuited the 3.3v pi and ground more times than I should've, and I think that might be the cause of all the damage. So would excessively short-circuiting basically mean that there's never gonna be enough power to light up the LED then? What can I really do now?

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rpdom
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Re: Shortcircuiting...

Sun Nov 17, 2013 7:42 pm

If you'd short circuited 3.3V and GND on the GPIO too much your Pi wouldn't boot properly, so I doubt that is the case.

I'd check your wiring. The basic test is:

Pin 1(3.3V)----[Resistor]------|LED>|-----Pin 6(0V)

The resistor should probably be somewhere roughly around 470 Ohms (off the top of my head without checking - it depends on the LED you are using).

Make sure you put the LED the right way around. Typically it will have a flat spot on one side and that should go to 0V.

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FTrevorGowen
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Re: Shortcircuiting...

Sun Nov 17, 2013 7:43 pm

justanoob wrote:
DeeJay wrote:Try just replacing the LED as a first step.
Sadly I've just tried replacing the LED again and it didn't do anything. Now that I think about it, I might've short-circuited the 3.3v pi and ground more times than I should've, and I think that might be the cause of all the damage. So would excessively short-circuiting basically mean that there's never gonna be enough power to light up the LED then? What can I really do now?
Does the Pi still boot-up? (w/o your "LED circuit")
What value of resistor were you using with the LED(s)?
Do you have access to a multimeter?
(See also @rpdom's post just before mine)
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

justanoob
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Re: Shortcircuiting...

Sun Nov 17, 2013 8:17 pm

So I'm pretty sure I had the LED in the right position, and I basically just did what I was told by my TA. But I ended up messing around with too much I guess. To be honest, I don't know what the value of the resistor is, since we just got all their Raspberry Pi stuff in a bundle and we weren't given any specific info about it. The Pi still boots up perfectly and I can do everything else I want to do on it besides lighting up the LED.

Here's some images of what it looked like when it worked:
Image
Image

And no, I don't have access to a multimeter.

klricks
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Re: Shortcircuiting...

Sun Nov 17, 2013 9:36 pm

Hard to see from the image but the red wire looks to be very close to the other leads on the LED and resistor. As I already mentioned if red wire accentually touched the LED or resistor lead then the LED would have been destroyed as the resistor would have been bypassed.

(Hint use macro mode on your camera for close-up photos so they will be in focus).
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

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DeeJay
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Re: Shortcircuiting...

Sun Nov 17, 2013 9:40 pm

klricks wrote:Hard to see from the image but the red wire looks to be very close to the other leads on the LED and resistor. As I already mentioned if red wire accentually touched the LED or resistor lead then the LED would have been destroyed as the resistor would have been bypassed.

(Hint use macro mode on your camera for close-up photos so they will be in focus).
justanoob says he/she has replaced the led...
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justanoob
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Re: Shortcircuiting...

Sun Nov 17, 2013 10:14 pm

klricks wrote:Hard to see from the image but the red wire looks to be very close to the other leads on the LED and resistor. As I already mentioned if red wire accentually touched the LED or resistor lead then the LED would have been destroyed as the resistor would have been bypassed.

(Hint use macro mode on your camera for close-up photos so they will be in focus).
I had the red wire touching the LED/resistor. So does that mean that I shouldn't be doing that then? Cuz I don't get how else you can do it.

klricks
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Re: Shortcircuiting...

Mon Nov 18, 2013 12:33 am

justanoob wrote:
klricks wrote:Hard to see from the image but the red wire looks to be very close to the other leads on the LED and resistor. As I already mentioned if red wire accentually touched the LED or resistor lead then the LED would have been destroyed as the resistor would have been bypassed.

(Hint use macro mode on your camera for close-up photos so they will be in focus).
I had the red wire touching the LED/resistor. So does that mean that I shouldn't be doing that then? Cuz I don't get how else you can do it.
Your circuit should be something like this. I have labelled the connection points A, B, C

Black Wire----- (A)------[LED]--------(B)-------[Resistor]--------(C)------ Red Wire

From your photo it looks like the red wire at (C) is dangerously close to touching point (B). If you let the red wire touch point B then the LED(s) would be blown out.


.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

justanoob
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Re: Shortcircuiting...

Mon Nov 18, 2013 1:46 am

klricks wrote:
justanoob wrote:
klricks wrote:Hard to see from the image but the red wire looks to be very close to the other leads on the LED and resistor. As I already mentioned if red wire accentually touched the LED or resistor lead then the LED would have been destroyed as the resistor would have been bypassed.

(Hint use macro mode on your camera for close-up photos so they will be in focus).
I had the red wire touching the LED/resistor. So does that mean that I shouldn't be doing that then? Cuz I don't get how else you can do it.
Your circuit should be something like this. I have labelled the connection points A, B, C

Black Wire----- (A)------[LED]--------(B)-------[Resistor]--------(C)------ Red Wire

From your photo it looks like the red wire at (C) is dangerously close to touching point (B). If you let the red wire touch point B then the LED(s) would be blown out.


.
So are you saying that the red wire should never directly touch the LED or the resistor then?

obcd
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Re: Shortcircuiting...

Mon Nov 18, 2013 7:19 am

The red wire should never be connected to the led directly. You probably blew your second led as well by connecting it to GND and 3V3 directly. The red wire should be connected to the resistor, and the other end of that resistor should be connected to the positive side of the led.
A led always needs a resistor in serie to limit the current.
The holes of your breadboard are connected to each other, usually in a line pattern.
Not all breadboards are equal when it comes to that.

klricks
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Re: Shortcircuiting...

Mon Nov 18, 2013 2:00 pm

justanoob wrote: So are you saying that the red wire should never directly touch the LED or the resistor then?
No. I am saying you must keep the leads of all the components from accidentally shorting together or making contact where they shouldn't. Either rearrange the components on the bread board so there is more space between the leads and no danger of shorting, and/or add insulation to the LED and resistor leads.
What I do is to strip insulation from some spare wire and slip that over the component leads. Or you can buy insulator tubing or 'heat-shrink' tubing.

The LED must have a resistor in series (in-line). The resistor and LED can be swapped however.

Like this:
Black Wire ----- (A)------[LED]--------(B)-------[Resistor]--------(C)------ Red Wire

Or like this:
Black Wire ----- (A)------[Resistor]--------(B)-------[LED]--------(C)------ Red Wire

As long as the LED is oriented correctly, either of the above circuits would work.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

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