Hi,
I´m starting my first project with Arduino Uno, so beginners question coming..
I was wondering which is the best way to drive 5*5W infrared leds simultaneously from a single pin of Arduino Uno? And yes I´m using them only simultaneously.
Do I just put 100 ohm resistor (or maybe 47 ohm?) in front (Ground) of every single led? Or do they need a resistor at all? Maybe there´s some better way better way to do this.. I bet there is.
Thanks for your answer.
,Tomi
Do you mean turning on/off or dimming.
Arduino can control small 20mA LEDs, but not 5watt LEDs.
You need a power transistor (logic mosfet) or constant current LED driver to control five 5watt LEDs.
How are you going to power them. Batteries or mains power.
You also need serious heatsinking for 25watt of LED.
Leo..
An IR LED can be run at 1A with 5V to get the 5Watt figure.
However, this is only if the duty cycle is below 1%, as it is when the IR is used to send remote codes.
Regardless, the Arduino will not push anything near 1A.
If this is your first project, you should do something you understand a little better. Or at least explain to us what it is you're trying to do.
I´m working on grow led light and it needs IR leds. I use external power to run them of course. No dimming, only ON/OFF. I guess I understand the code better than these old school electronics. I got one mosfet here, but it is IRF641.. is it something like IRF530 you are talking about? how do I connect that mosfet then? And I got a big heatsink with 3* 12v fans to cool the leds.
,Tomi
What role does the Arduino play in this.
Maybe a mains powered LED driver and a plug-in timer is all you need.
Do you have a link to these IR LEDs.
Leo..
I´m going to use WS2812B´s along with IR leds, so that´s why I need to use Arduino. Here´s the link to Ebay where I bought the IR leds:
(5W with PCB)
Not the easiest project for my first one I admit, but you got to have some challenge right? Well, I did the blinking led-sketch aka "hello world", so I guess I´m good to go :). Done tons of research though.
,Tomi
Seems these LEDs have a Vf (working voltage) of ~2.4volt and a working current of ~2Amp.
If you would power them from 5volt (WS2812B supply) with current limiting resistors, you would need 10Amps and loose half of the power in the CL resistors.
Five LEDs in series on a 12volt/2Amp supply (5 * ~2.4) isn't possible, because you need some extra voltage for the CL resistor.
A 24volt supply (or old 19volt laptop supply) could work.
You need a switching constant current (2Amp) LED driver with PWM input (on/off) with that.
Couldn't find one on ebay.
Leo..
I got 4 * (70-90V, 540-560mA)-power supply´s along with one 12V-supply, which I was planning to use. I measured that one of those gives me 97V without charge. And I´m never going to drive those WS2812B´s full white.. Only red, green or blue and sometimes some mixed colors. Going to use 50pcs of WS2812B´s.
What do you think? Do I got enough power for this set?
,Tomi
Samsara_Exit:
I got 4 * (70-90V, 540-560mA)-power supply´s along with one 12V-supply, which I was planning to use.
??
WS2812B LEDs expect a regulated 5volt supply.
Anything over 5.3volt is going to fry them.
50 WS2812B LEDs * 60mA = 3000mA = 3Amp.
You need a 5volt/3Amp supply for those LEDs.
Leo..
I´m never going to run them in full white as I said. 20mA each if red, green or blue, am I right? That´s how I calculated it. Even if I run those leds 40mA each it should be enough. I connect those leds in series.
Am I totally wrong here?
And does those leds really need regulated 5V? I´ve thought they would´t. If this really is the case, I have misunderstood it somehow. 13*5V=65V. My power supply gives me 70-90V. Could I use some sort of resistor to cut the extra current from them? Or do I need to add couple of extra leds to one serie?
Does those "normal" 5W-leds handle extra current differently?
You can't connect digital LEDs in series.
Leo..
Ok, well that´s good to know :). I mistakenly thought that WS2812B act like a normal 5W led. Good thing is that, I didn´t fry my new leds and that I actually didn´t paid anything of those 70-90V supplys , but now I really need to find the correct 5V, at least 2.5A ( would´t hurt if more) power supply for those. Thanks for this advice Leo.
Actually it might be easier to find and maybe cheaper to use 2 or more smaller power supplys. We´ll see.
But now once this voltage-case is closed, I´d like to go back to my first question. How do I drive those IR-leds from a one pin? Just ON/OFF and no dimming. 5 * IR-leds to one pin. Which kind of mosfet and connected how?
And Leo.. Where did you get that 2A current for one IR-led? I see only 700mA. By the way.. Yesterday after reading this:
I tested one IR-led and powered it straight from USB using 100ohm resistor and it worked just fine. How´s that possible if it takes 2amps? I just don´t get it.
And one more thing.. Why do I actually need PWM with these? I thought I use only HIGH/LOW.
,Tomi
So you want to switch the LEDs with a mosfet, not with a constant current driver.
The mosfets mentioned in a previous post are no good.
They need ~10volt at the gate to turn fully on, something the Arduino can't deliver.
You need logic level mosfets.
You mentioned 5watt LEDs.
If LED Vf is ~2.4volt, current must be 5watt / 2.4volt = ~2Amp for 5watt.
~700mA through the LED would be 2.4volt * 0.7Amp = ~1.7watt.
Less current is ok, but you will get less light too.
The link explains how to drive a 20mA IR LED. 1.2volt * 0.02 = 0.024watt.
20mA is not a problem for an Arduino pin. >40mA is.
The LED would get ~0.0624watt when powered from USB through a 100ohm CL resistor.
Leo..
Thanks. That explained a lot.
Maybe I should really think about that constant current instead of mosfets. I found this pic linked below. Gets a little confusing at first sight I´ve to say. Now I understand why I need PWM at least, but how do I calculate those values of resistors, transistor and diodes for 5*5W leds? This is the hardest part for me.. never gone this deep to electronics.
Well, It´s just good to learn new things I believe.
So I will need to use some led driver because of Arduinos limited 40mA per pin.. Am I right? Which kind of led driver I´m not sure.
Oh,Wawa said that above: "constant current (2Amp) LED driver with PWM input". Is that the only way out here?
Would this help?:
Here´s a 10amp version, but I´m not sure does it come with PWM:
Here´s some Youtube link to control 4W led. In this video a mosfet is still used to connect the Arduino to this circuit. Not sure if I need that or not:
All help is appreciated with these calculations.
Thanks a lot already.
,Tomi
To sum it up, is it easiest for me to reduce the amount of IR leds to 4 and buy 2 of these 5amp PWM led drivers:
So what else would I need? Which voltage should I give to this led driver? Is it somehow possible to take those 2 extra amps in use and connect fifth IR led? Pretty confused here, but I feel that this is the way to go.
,Tomi
You want your power supply voltage to be a couple volts above the Vf of your LEDs if you want the best efficiency. If you're going to put all four, 2.4V LEDs in series then you'd want something above a (4 * 2.4) 9.6V supply, so a 12V supply would be good. If you're just using two in series, with two drivers, then a ~6V supply would be good.
But since you're building a grow light you really want to be using mains power for these LEDs, and then you can just use a relay to switch the mains power to the LED driver on/off. LED drivers powered from mains are widely available and inexpensive, but you do need to make sure you find a driver with the same Vf and amperage to your LEDs.
The big problem here is the dubious specification of your IR LEDs. They're described as 5W but the product page states that they are 2.6Vf and 1.2A (or 3.12W). I would suggest sucking it up and buying a 3W driver and underdriving the LEDs -- or find some LEDs with some intelligent documentation.
So you're making grow lights, that only need a simple on/off function?
Or are you specifically trying to control timing and exposure to manipulate node spacing and flowering for some particular experiment? You did say you only want them all on simultaneously but then you're buying smart LEDs for some reason.
What are you growing and what wavelengths do you need to hit?
Guidance you get will be a lot more relevant if you give pertinent details on what your goal is instead of cluing us in when you're already halfway concluded in things you erroneously made your mind up on.
What power sources do you have available? What total light output per wavelength are you aiming for? How much control do you need over timing and brightness? Is this an automated system involving sensors? Why do you want this to use an Arduino if it's likely not necessary? What's with the 1-pin restriction?
Allright,
I´ll try to make this as clear as possible.
My aim was to build 300W grow led light. I want simultaneously control (ON/OFF, no dimming) 4 or 5 5W IR leds and to be able to do that via Arduino. I also want individually control 50 pcs of WS2812B´s via Arduino, cause I want about 25/50 of them to be ON when growing (or HIGH, no dimming, other 25 then LOW) and when blooming 50/50 to be ON (or HIGH).
The reason why I need to use Arduino for this job is because I want total control to wavelengths of every of those 50 pcs of WS2812B´s. Right now I´m not going to be able to measure the exact wavelengths of those leds, but I´m going to be in the future. Right now I just want to build a grow light with this feature. The possibility of changing individually the colors of 50pcs of RGB leds and turn them individually ON/OFF as well (no dimming). For IR leds, only possibility to turn them ON/OFF at the same time or as a group and of course no possibility to change the wavelength (no dimming).
This first project will do just that. No timer, no nothing fancy. Oh well.. one button to change the light to be on GROW or in BLOOM state. In the future, if i ever succeed in this first project, then it´s possible that I add some sensors and other stuff. But not right now. "What's with the 1-pin restriction?".. well, I could just as well use 4 pins or 4 leds, but I just want to learn to do that. Maybe in future I need to use even more IR leds in one light. Then this skill will become more important.
I really hope that this made it clear for you.
By the way.. I already have ordered 5pcs of 12V relays. I might have use for them now.
,Tomi
Thanks for the further details.
A few things to know-
You cannot "pick wavelengths" with an RGB LED. An RGB LED is simply 3 LEDs in one package. Imagine 3 separate LEDs, red-blue-green. You cannot give your plants yellow wavelengths just by turning on a red and green LED. It may appear yellow to your eyeballs, but that's in your head, literally. You understand you cannot change the wavelength of the IR leds, the RGB ones are the exact same scenario.
Again, this application does not call for WS2812's. I know all the cool kids are using them, but let it go. You are much much better off finding white LEDs with known spectral power distributions.
Are you aiming to dump 300W into the LEDs or is your 300W figure based off of an incandescent lighting equivalent? There is a huge difference.
Of course I cannot pick wavelenghts.. I know what RGB led means. 0-255. And I don´t need a single white led in my light. If you don´t understand why, then you don´t know much about grow lights. And if I understood the last line right.. 300W to leds. Yes. right now it´s going to be a little less.
And the reason I picked these IR leds, was because they were the only ones with the right wavelength.
Am I this bad in explaining things.. I don´t know, but this starts to feel hard.
,Tomi
