Go Down

Topic: Arduino on a Breadboard: problem with 7805 voltage regulator, blew up LEDs! (Read 2496 times) previous topic - next topic

BernieG

What you SHOULD have learned:
1-there was no "surge" to begin with. It was your inexperience using the meter, nothing more.
2- the LM7805 WAS regulating on power up, just as I said.
Ys, I actually learned that.

3- you miswired the first 330 ohm resistor causing the led to "blow up"
No, you are wrong about this. The first led blew up, cerainly because at my first attempt I had the LM7805 in reverse, and sent 12 volts to the Led.

4- You are too inexperienced to be using a 12V power supply capable of delivering 20 to 30 A because the first time you miswire something you're going to blow something up or start a fire. Get a different supply and get that computer power supply far away from your electronics before you hurt someone.
I will get a better power supply, when I can. Even if I consider myself as being inexperienced, I have been using this computer power supply since about 2 years without any kind of problem. Not saying it cannot happen, but puting things in perspective.

raschemmel

The first resistor is still connected with both leads in the same row.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

BernieG

Yes it is true. Zoom in on the both photos. The led is on because your connected the SECOND 330 ohm resistor correctly. You can see the first resistor with BOTH leads in the SAME ROW ! (in both photos ).
No, you are wrong on this, sorry. I removed the 2nd resistor, and it is still working just fine. The pictures do not show the connection well enough.

You need to stop listening yourself and start paying attention to the experts you are consulting. You have been wrong on all counts from the start:
1- You blew up the led. The led didn't blow itself up.
2- there was no surge
Sorry man, but YOU should get down from your horse, and stop insulting my intelligence! Where did I say I was not wrong somewhere? I don't need you to tell me that. I know I am a beginner, and as such feel that it is perfectly right for me to make some mistakes.

Obviously the led did not blow itself up! Telling me that is borderline with an insult.
Yes, there was no surge. But as a beginner, I did not know I had to setup the range BEFORE measuring, as most of the time, the measure is just fine with auto-range.

So, among the important things I learned today with this, one of them is to stay far away from you.

ChrisTenone

I think it's very frustrating to continue to say the resistor is not miswired. Here is a section of your picture that clearly shows both leads from the resistor plugged into the same row on the breadboard:


What, I need to say something else too?

raschemmel

Look at the first photo you posted. The resistor has both leads in the same row.
The led was still working because the second resistor is connected correctly.
Removing the first resistor doesn't affect the led because the first resistor had both leads shorted to each other.  Being angry with me for telling you that you still do not see the reason why the first resistor has nothing to do with the led still working doesn't change the fact tgat Mike was right about the resistor. I'm not insulting your intelligence. I'm criticizing your powers of observation ( or lack thereof. You are very stubborn   this will work against your in your efforts to learn electronics. What you should be saying us "Oh, now I see it ! Thank you Mike for pointing that out " instead of "No, you're wrong, I removed the first resistor and ithe led is still working". (obviously because of the second resistor) We are going to keep repeating this dialog untill you admit your error .Why .?  Because you can't learn electronics if every time you make a mistake you deny it and sweep it under the carpet by removing the miswired part  and saying it's not relevant.  I didn't insult you. You over reacted.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

BernieG

Look at the first photo you posted. The resistor has both leads in the same row.
Yes. And?

That's were I fail to see a mistake. If I want to get 660 Ohms resistance with 2 x 330 Ohms resistors, should not they be connected serially, one behind the other? Here is a quick draw of the connection, as it was when I took the picture.



Sorry it's on the side and not straight up.
If this wiring is wrong, I will be happy to learn why, but to me it's just 2 resistors added one to another.

And I did believe this was basically impossible to see on the picture. But I fully accept to be wrong, as soon as I know why.

You over reacted.
Sorry then.

ChrisTenone

All of the holes in a row on a solderless breadboard are connected. The row labled 2 has one side of the resistor in hole 2a, and the other side in pin 2c. 2a and 2c are connected under the surface by a strip of metal.

So in effect that resistor is not in the circuit. If you had the current limiting resistor hooked up like that, it did not limit the current, and explains why your led burnt out.
What, I need to say something else too?

BernieG

I realized that afterward, during this discussion, that 2nd resistor has no effect. But it IS a 2nd resistor, otherwise there would have been no current at all going to the led. The connection between power + and the led is being made by the 1st resistor, so this mistake (wiring a 2nd resistor believing it would double the Ohms) cannot be a reason for those Leds problems.

ChrisTenone

12 volts is less likely to blow up your LED than is no resistor. The mis-wired resistor must have been the only resistor when you first tried it. Sometimes these things happen.
What, I need to say something else too?

raschemmel

Quote
But it IS a 2nd resistor, otherwise there would have been no current at all going to the led. The connection between power + and the led is being made by the 1st resistor, so this mistake (wiring a 2nd resistor believing it would double the Ohms) cannot be a reason for those Leds problems.
Wrong:

Your statement should read:



Quote
But it IS a 2nd resistor, otherwise there would have been no current at all going to the led. The connection between power + and the led is being made by the 2nd resistor, so this mistake (wiring a 2nd resistor believing it would double the Ohms) cannot be a reason for those Leds problems.
This statement would be the same as saying :
"the 1st resistor had both leads connected to the same row , the circuit was OPEN.
Adding the 2nd resistor created a current path to light the led.
If the original led had been burned out by the reversed 7805, then the led we see lit must be a replacement led that did not light until the 2nd resistor was added.

In this respect you are correct that the miswired first resistor only resulted in an OPEN circuit and could NOT have burned out the led but WAS responsible for it not lighting because the circuit path was not complete.

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

be80be

If you look at that picture the led is in roll 1 the resistor is in roll 2.
Roll 1 has a black wire going some where thats not shown.

I put some lines on it so you can see it more clearly His beard board must not be connected on the the plus and minus rail.
 

Grumpy_Mike

If your initial fault was the regulator being wired wrong you should have admitted it as soon as it was pointed out to you.

The fact that you blew up an LED means you did something else wrong. With only one resistor of 330R and 12V you had 36mA going through the LED. Most LEDs are only rated for 20mA so you exceeded the maximum current. That might be enough to blow it up, especially if it a cheap one from the Far East.

However given the OP's response to the information he has been given, it is likely he is totally unaware of any other wiring errors he made, so in that case a rigorous analysis is impossible.

It is not the schematic that is wrong but how you converted that schematic into physical wiring. In other words what you wired with the second resistor is not how it is connected in the schematic.

raschemmel

Quote
a rigorous analysis  
I like that term.

sounds like a Newbie's worst nightmare... ;D
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Go Up