What happens if I don't use a resistor on my LED? Short term Arduino Test
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- เผยแพร่เมื่อ 20 ธ.ค. 2020
- People smarter than I am say that you ALWAYS need to put a resistor inline when you attach an LED to an Arduino. But what happens if you don't? I made a light-hearted, non-scientific 24 hour test to find out.
How do YOU think I could do a better long term test?
This is Will It Blow Up Episode 2
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Damage is not really a quantifiable value, instead just measure the current drawn. Check it against the data sheet for the led and the mcu. If you are exceeding the maximums then you can assume you are doing damage. By how far you are exceeding the max should be roughly proportional to the damage caused and inversely proportional to the expected life of the parts.
Right. In the simple 1 day test since it didn't "blow" there's no real way to quantify that damage.
Oh and current measurements are coming in the next video.
@@AnotherMaker I like to collect LEDs from around 1990, either pristine, or used constantly for 30 years. They are different. Gotta say, they *do* wear out and go dim. Have done visible damage to fresh ones too, even briefly, at less than 25mA.
How do you connect 8 led to close and outer using 1 resistor?
Staying in the safe Operating range is important....You can also take into account the current draw vs the luminous intensity.... I try to maintain a consistent LED brightness for certain product lines.. Depending on the LED, you can get away with no resistor if you place a Duty Cycle on the GPIO pin... ie 20% Duty Cycle @ a frequency that the human eye does not detect as flicker.. This will reduce the average current but may still have peak currents to tend with depending on trace inductance ..
That's a great idea. Thanks for this. More testing coming soon.
you could put an amp meter in series between the Mega's pin (positive) and the LED's cathode pin to see what current the LED got to chew ?
100% - My best two meters died so hopefully right after Christmas I'll get a new one and can take readings that I trust.
@@AnotherMaker that'd be a nice christmas gift :)
INA219 perhaps
@@bigpickles yeah that'll do fine. I ordered an INA216 for other use myself but not yet received it (pesky Ali :D)
@@maicod lovely. I have a bunch of 219s in use at the moment. Great little modules. I believe the shipping globally is slow, but if there is no local stock there, perhaps an opportunity for you to import and resell parts locally :)
by mistake i connected 2 LEDs in parallel with the 5v and GRD pins from the arduino board and one of them burned does that will affect the arduino board or my laptop (the arduino was connected with the laptop) ?😢
Since all the leds care for is the voltage, you could power two leds in series instead as well and it would be just fine
If I use bread board, Arduino mega, 8relay, 6 pumps, 6 moisture sensors. Do I need transistors?
You normally don't. The relays and sensors (USUALLY) have built in resistors or you can use the pullup resistors in the arduino, but that would depend on the instructions for the sensor itself. MOST moisture sensors normally come with a little circuit board that handles all that and you just run 3 or 4 wires from that board to the arduino.
Have you uploaded basics of coding a ARDUINO on TH-cam or some other application. Please tell, I want to learn coding skills.
If you want a good breakdown of the basics, check out Paul McWhorter on TH-cam.
I agree with Miles. Paul is fantastic for breaking stuff like that down step by step. I do have the code for all my recent videos here github.com/mudmin/AnotherMaker but Paul is the best when it comes to teaching.
By the way,I would really like to see more Videos like this.
Thanks. They're goofy, but they're fun to make.
Which resistor should I use?
Loving the Bee Gees humor :)
That means a lot! I'm glad someone gets it!
@@AnotherMaker its probably my age :) I like the Bee Gees
You should compare the brightness of these LEDs before and after connecting them without resistors. But you would have to use a constant current source to check if the brightness changed, to get accurate results.
Yeah. They looked the same with the eye test but I need a more scientific way for round two :-)
@@AnotherMaker Could you use a sensor like a photoelectric resistor to measure their brightness?
Some boards have an internal resistor. Do these?
I'm sure there's something in the chip but the resistors that most people think of are pull up resistors that I BELIEVE are only available when the pin is set as an input.
how much ohms required if a connect a battery of 3.6Volt and then touched it with a led of 3V of 1 W ? is it 2ohms ?
R=Resistance/Ohms
U=Volts
P=Watt
I=Ampere
P = U x I
1 = 3.6 x I so I = 3.6 : 1
R = U : I
R = 3.6 : 3.6
R= 1 Ohm
I have a uno in front of me right now with a dead pin (stuck on) due to not using a resistor. It killed that pin, but not the others.
It definitely happens. It didn't happen here, but I've heard of it happening.
I do agree with you about using a resistor with the Arduino, as each pin can only supply so much current. In my case, I am perfectly fine with using 1K resistors with my LED's. I have a feeling that if you hooked the LED's straight to a 5V power supply, the LED's may be fine with it at first but won't last very long.
If the LED is bright enough for your needs, then you won't go wrong with a 1k resistor.
It depends on the rating of the led and the supply. Most normal leds can't handle 5V and will burn out immediately. When your 5V supply can't handle more than a few milliamps of current at the rated voltage, then the voltage drops, which will then be safe again for your led.
Can I use a 1k resistor for 6 led lights im using 3v led lights atm will 3v work ok with a 1k resistor on 7.4v batterie
You can probably get away with it but you should use one resistor per LED because when they are in series like that the first one may be drawing more current than the one after it. So you may not get the protection you are hoping for
@@AnotherMaker im using 1 resistor connected to 2 led lights its ok so fah
If you had put the LEDs across a five volt supply with no current limiting, the LEDs would have been killed quite quickly (in a few milliseconds). Obviously therefore, the MPU is limiting the output current, and I'd expect that to be at or slightly less than the 20mA limit for the 2560. I don't believe this kind of current is going to damage a GaAs low intensity red LED in any short amount of time, however it *might* cause them to dim or fail over many months.
More importantly though, you don't know how the 2560 is limiting the current internally. The manufacturer recommends using a resistor to limit the current, so there's probably a good reason for that. You're much more likely to damage the 2560, and there's no way to quantify that damage except "it works" or "it's broken" even if the damage from doing this happens slowly over time. Perhaps the internal current limiting is there to prevent damage in cases of a short inrush current to the downstream electronics (eg capacitance) and without causing the processor to reboot, but it's definitely not there so you don't have to use a current limiting resistor.
Fantastic response and I totally agree.
Damage is due to thermal/physical deformity of the physical structure of the components
It can be molecular - misalignment of doping, thermal expansion, or even chemical rebonding, or just melting apart and oxidising (burning)
It can be macro - a capacitor essentially being pulled in on itself til it contacts and shorts
In the worst cases, it literally explodes from repelling electrical force
I just want to know: Why do you NEED a resistor, rather than feeding the LED it's rated input DC voltage and current? Like, surely neither the LED nor the Arduino cares if the LED is getting it's ideal input power - but everyone, EVERYONE, says to put that LED in there, and for a couple LEDs I don't see that being a huge problem but for projects with lots of LEDs it kind of seems like that could potentially bea pretty significant power waste. :/
The general rule is that you need a resistor for 1 of 2 reasons. The LED will draw as much current as it can get so if the device can offer a lot of current, the LED will draw so much that it will eventually burn out, or in the case of an arduino, it will try to pull more current than the pins are designed to provide and could damage the arduino
@@AnotherMakerThat is actually a bit misleading. The current is not simply given to the led and the led will not just draw unlimited current without a resistor. The current will be determined by the internal resistance of the led and the voltage given to it. It will not burn out when the voltage for the led is within it's capabilities.
A resistor is not actually limiting the current. Is simply drops the voltage down depending on the resistors value, which leads to the current being reduced as well, but not limited. For the led it doesn't matter if there is a resisor in front of (or after) it or not present at all, as long as the voltage is low enough, so that it's power rating is not exceeded.
in a sense an led is also a resistor, which can not hold much current, due to its small wire inside.
Whe the "little resistance wire" in the led breaks there can be two scenarios. Either the wire breaks and opens the circuit or it welds the anode an cathode together, which is a short circuit, that heats up and burns out.
@@Noxoreos That is a better explanation. Thank you.
I did an experiment with LEDs and NO resistors: th-cam.com/video/bLnyO4rOOlc/w-d-xo.html No arduino used in mine but the LEDs have been working fine for about 4 hours every evening. I think since they are flashing LEDs each one is only on momentarily and there are around 95 LEDs sharing the current.
That's really awesome.
not easy to plug in
Resistor rather. Lol
I have no clue what I’m doing…. Lol
Ok, this is clever, I appreciate it. You are gaslighting. Am sure the current on each pin is limited by the MPU so it does not burn the the bonding wire. Put a little 0.2 ohm resistor in series, and lets see the draw.
Agree. That's the next step. I've actually had my best meters die in the last few months. My fluke screen went out and my big meter's been flaky. I'm hoping to find a new one under the tree this year so I can take measurements that I trust.
I burned my self because I didn’t use one
Ouch. Sounds like it was drawing a lot of power.
@@AnotherMaker yea I striped a usb cable plugged it in to my computer and I was holding the wires together and it burned me. Wasn’t that bad probably 1st degree burn.