White LEDs are questionable because they're typically blue LEDs with yellow phosphors. Whether the yellow light is within the "red" range that plants accept is not something I know.
Easiest would be to get some T8 led tubes.
Plug: fluorescents don't flicker either if you use a proper electronic ballast. Did I mention that I think fluoros are underrated?
White leds make absolutely no sense. If something is going to be DIYed, then it's just easiest to pick those deep blue and deep red (i.e., 445/450 nm and 660 nm) LEDs. There are specific "grow light" LEDs which are like white leds, but with red phosphor, but I can't see the convenience in using just one type of LED.
But speaking of flicker: If I did decide to use PWM dimming (either via an off the shelf controller, or a DIY Arduino solution), and I found flicker to be objectionable, is there any reason I couldn't use some electrolytic caps to smooth it out?
Easiest would be to get some T8 led tubes.
I wouldnt worry about red/blue leds. White lets are blue with phosphor. There is a lot of information about corals/weed using led lights. I would just look at someones build. Get some crees and a meanwell power supply. Supplement the day hours.
White is the wrong color for photosynthesis (t will work but you're throwing energy away...)
White is the wrong color for photosynthesis (t will work but you're throwing energy away...)I guess you didn't read either my original post nor the reply...
But speaking of flicker: If I did decide to use PWM dimming (either via an off the shelf controller, or a DIY Arduino solution), and I found flicker to be objectionable, is there any reason I couldn't use some electrolytic caps to smooth it out?No, it will increase the power consumption and could even damage the transistors.
Also note that PWM is not a very efficient way to control the brightness. LEDs are more efficient at lower currents so it's more efficient to just reduce the forward current. PWM is often used because it's more convenient and the spectrum of some phosphor coated LEDs can change with the forward current so sometimes it's better to keep it constant and reduce the duty cycle.
White is the wrong color for photosynthesis (t will work but you're throwing energy away...)I guess you didn't read either my original post nor the reply...
You're assuming that was what I was replying to.
(I messed up the quote... now fixed)
Do you need a different color for when humans are in the room? Won't it be enough to just switch on the LEDs when the humans are away? That would simplify things a lot (you even could have a light sensor and turn off the LEDs when there's enough normal light in the room)
One could, of course, have a motion sensor to detect human presence and automatically switch from the pink grow light to white when people are around. :p
this being an engineering forum, I think we can all appreciate "Because I can!" as a reason to do something unnecessarily complicated.
One could, of course, have a motion sensor to detect human presence and automatically switch from the pink grow light to white when people are around. :pYou mean like one of those new offices where you have to stand up and wave your arms every ten minutes to keep the lights on and not freeze to death?
this being an engineering forum, I think we can all appreciate "Because I can!" as a reason to do something unnecessarily complicated.The motion-sensor part in particular could get easily become... "interesting".
White LED are less efficient for grow but they are so much cheaper, especially when you want to build something bright, like this -> https://www.circuitsathome.com/diy-2/high-power-led-grow-light-a-build-log . This light is now ~3 years in operation; combined with hydroponics it gives outstanding results. Peppers are very happy.
Another thing I'm experimenting with are lightweight fanless fixtures made with small 100 mA emitters. I hang some of the lights vertically around the plant to provide intra-canopy illumination.
$20-30 for a 5m strip of 660/445nm grow light LEDs (totaling 72W) doesn't seem that expensive to me.
Yes, it's a lot more than white LEDs, but given how much more efficient it must be, probably makes sense in the end.
If they're cheapo 12V LED strips with built-in resistors then use an Arduino and a logic-level MOSFET.
If they're high-power LEDs then use an Arduino and an LED driver which has a PWM input.
But speaking of flicker: If I did decide to use PWM dimming (either via an off the shelf controller, or a DIY Arduino solution), and I found flicker to be objectionable, is there any reason I couldn't use some electrolytic caps to smooth it out?No, it will increase the power consumption and could even damage the transistors.
Also note that PWM is not a very efficient way to control the brightness. LEDs are more efficient at lower currents so it's more efficient to just reduce the forward current. PWM is often used because it's more convenient and the spectrum of some phosphor coated LEDs can change with the forward current so sometimes it's better to keep it constant and reduce the duty cycle.
If they're cheapo 12V LED strips with built-in resistors then use an Arduino and a logic-level MOSFET.Hence my still unanswered question: Could one use an Arduino to create PWM, smooth that to analog, and then use that to drive a MOSFET or whatever to allow flicker-free control of the LEDs?
Or were you suggesting PWM all the way to the LEDs?
If they're cheapo 12V LED strips with built-in resistors then use an Arduino and a logic-level MOSFET.Hence my still unanswered question: Could one use an Arduino to create PWM, smooth that to analog, and then use that to drive a MOSFET or whatever to allow flicker-free control of the LEDs?You could do that but it's tricky and there's no need.Or were you suggesting PWM all the way to the LEDs?
PWM all the way to the LEDs.
The standard Arduino "analogWrite()" function outputs a 1kHz PWM signal so you're not going to see any flicker.
Just PWM the LEDs. Filtration doesn't make any sense.
LED efficiency is practically constant unless you are near or exceeding recommended maximum current rating. Maximize efficiency, lifetime and ease thermal design by running the LEDs at slightly below recommended maximum current. PWM at high enough frequency so that you don't visually see the flicker. Anything above, say, 200-300 Hz, works. I guess the Arduino library uses something around 1 kHz which is optimal.
The standard Arduino "analogWrite()" function outputs a 1kHz PWM signal so you're not going to see any flicker.Unfortunately that's incorrect. It's around 490Hz, which at low duty cycles causes very obvious flicker.
I know from personal experience that I readily see annoying flicker with Arduino's 490Hz PWM at duty cycles below about 30%. I also routinely notice (and am annoyed by) flicker in dimmed LED lighting at bars and restaurants here, which I assume are using COTS LED dimmers. My concern about flicker, and willingness to go to significant lengths to avoid it, are because I know I am sensitive to it and know that it annoys the living shit out of me.