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Topic: Resistors not needed (Read 599 times) previous topic - next topic

carmelagarcia

I have looked a few different tutorials to do a simple get the LED to blink.
They all include resistors and I did it exactly like the picture.
I tried it WITHOUT the resistors (ground to the short end of the LED) and it worked perfectly.
I've read in other places that it can cause damage to the LED if you don't use a resistor.

I'm now trying to do a project where you push a button to get the LED to light up (using resistors) but that's not working.


Any advice would be appreciated

Thank you!!
Carmela

Paul__B

#1
Nov 14, 2019, 12:29 pm Last Edit: Nov 14, 2019, 12:30 pm by Paul__B
I've read in other places that it can cause damage to the LED if you don't use a resistor.
And you will read about it everywhere here.  Damage to the LED and/ or the Arduino.  And you do not necessarily know straight away.  The LED may appear to work but slowly die, and the Arduino may do the same on the pin you were using.  How's that for a plan?  :smiley-eek:

I'm now trying to do a project where you push a button to get the LED to light up (using resistors) but that's not working.
Well, when and if you gives us the details (hint - read all the instructions for how to do so) someone just might be able to figure out why.  If there is enough information to do so.  :smiley-lol:

carmelagarcia

Thank you!
Is it possible to post a video/pictures of how it is/isn't working?
I know the code is right to do an LED blink (because it works when I don't use resistors), so it's just how you hook up the breadboard. I've looked at many examples and they don't seem to work. 

slipstick

Post the code that you know is right (then we'll know it's right too). Post one picture which shows exactly how your LED and resistor are wired and tell us the type of LED and the value of the resistor.

No videos needed...a video of an LED not lighting up is spectacularly useless!

Steve

MrMark

I tried it WITHOUT the resistors (ground to the short end of the LED) and it worked perfectly.
I've read in other places that it can cause damage to the LED if you don't use a resistor.
The output pins of the Arduino (and indeed any transistor) have some effective on resistance which limited the current enough that the LED was not immediately destroyed.  The current likely exceeded the rated limits of the Arduino and/or the LED so it is not good practice to do this sort of thing.

groundFungus

#5
Nov 14, 2019, 03:33 pm Last Edit: Nov 14, 2019, 03:34 pm by groundFungus
We need to know how the switch is wired.  An improperly wired switch (no pull-up, pulldown resistor) will not "work" right.

carmelagarcia

Post the code that you know is right (then we'll know it's right too). Post one picture which shows exactly how your LED and resistor are wired and tell us the type of LED and the value of the resistor.

No videos needed...a video of an LED not lighting up is spectacularly useless!

Steve
Happy to post a photo but how do  you upload the photo?

Grumpy_Mike

Quote
Happy to post a photo but how do  you upload the photo?
Read the how to use this forum sticky post, he bit about attachments.

larryd

No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

Paul__B

The output pins of the Arduino (and indeed any transistor) have some effective on resistance
About 47 Ohms in fact for the ATmegaxx8.  Figure from that.

noodlespinbot

thebigbrainorg.co.uk

JohnRob

I think you are confusing "working" with "working within the specifications of the parts".


Consider you have a 50# bag of cement.  Your friend Bill is working with you, you hand him a bag of cement.  He is able to hold it fine, so you conclude that it is OK for Bill to hold the cement bag.   You come back some hours later and the cement bag is on the ground.   Bill says:  " I couldn't hold it"  of course this conflicts with your observation that he could holding it fine earlier.

Use an LED without a resistor and you will discover your Arduino output is likely like Bill in the above scenario.

Now you have to decide if you want to use a resistor.

Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

12Stepper

Or use leds with resistors built in, which is (of course) still "using a resistor" just not a discrete one external to the led.

Downside is that they are "resistored" for a specific voltage.


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