Grow light for in house plants with Arduino using LED

Hello everyone! I am trying to build a little grow light for some plants to help them grow in the winter times and with the little available light from a gloomy window.

I already have an Arduino Mega 2560 for this project so I will be using this one.

I was wondering if anyone could advice in what would be the best way to approach this project in particular what "source light" would be best.

I already have a strip of Warm White LED 12v 3528 left from another project. I reckon the strip will be around 75 LED long. Ideally I would like to use this so that I don't have to buy extra materials but I also read that the best light to for plants are Deep Blue, Deep Red and White. So I am also considering the following options:

  • 16x Single strong 3W or 1W LED (8x red and 8x blue). Like these
  • Buying another strip of 12v RGB LED and have it permanently set to Violet/Purple. Basicly following this tutorial minus the smartphone part as I only want the Arduino Program to Turn the power ON for 12h and then OFF for 8h, nothing else.

I understand that all these options I will need a 12v power supply for the strip to be configured with the TIP31 Transistors like in the tutorial and this brings me to the next 3 questions:

  • What sort of wattage should the 12v LED strip power supply have 24,36,60...?
  • What power supply should I get if instead I decided to use the Single 1W or 3W LED?
  • Will any of these power supplies will be able to also provide current to the Arduino Mega? I would just like to have the all system taking up only 1 plug from the wall XD

Thanks a lot for any help you'll be able to give me!

Are you wanting to do this for fun or are you just wanting this done? You could just get an outlet timer and power a lamp if its the latter.

If its the former, im not sure where the power rating comes from as it would have to be dependent of the number of LEDs you are running, but any wall-wart style 12DC power supply with >1A should be plenty to power an LED strip.

I think the spectrum is important for best results - so the selection of light types might be best for a forum that deals with inside growing - or get some standard grow lights and then a simple program for the time with large enough relays or Triacs to switch the load

But the time inside the Arduino seems to creep a bit so a real time clock might keep you from needing to fine tune the time settings - or you could just go with a simple program of X time / minutes on and Y time / minutes off - would be also straight forward

@Dustin, I do want to do the project and learn more about Arduino. Plus I really enjoy these diy projects.

@Saildude, I tried to look up grow light but they are all either too expensive or not suitable for the space I want to put them. This said they all seem to follow the same configuration of LED (80%red 15%blue 5%white) so I am thinking of buying some single LED and try to replicate this mix.

What sort of wattage should the 12v LED strip power supply have 24,36,60...?

It depends on the power rating for the LED strip(s). If they don't give you a power rating they should give you current rating. Power is calculated as Voltage x Current.

Give yourself some safety margin... Don't push the power supply to it's limits.

What power supply should I get if instead I decided to use the Single 1W or 3W LED?

High power LEDs (1W or more) require a special [u]constant-current[/u] power supply. That would be separate from the Arduino's "normal" (constant-voltage) power supply.*

Will any of these power supplies will be able to also provide current to the Arduino Mega?

The regular 12V supply can power the Arduino and LED strips (as long as the power supply can supply the power/current). 12V [u]commercial/architectural LED bulbs[/u] have the constant-current power supply built-in, so they can also run from a regular 12V power supply if you find one that runs on DC. (Most of these are designed as plug-in replacements for incandescent bulbs that run from a 12VAC transformer.)

  • Regular little LEDs require constant (or "controlled current") too, but the current is limited with a resistor. Most LED strips use a resistor on each LED. But since the resistor often dissipates more power (as heat) than is consumed by the LED, a resistor as a current-limiter isn't efficient with high-power LEDs and of course you heed a high-power resistor. Resistors in LED strips are not efficient either, but at least the heat is spread-out.

For growing under LEDs you need special grow light LEDs, not the ones you use to light up your home.

They come in various colours mostly the blue+red variation (making your plants look purple), there are also full spectrum grow light LEDs which are rather close to white to our eyes.

Your "warm white" LEDs most likely give very poor results for providing the wrong spectrum. Good old T5 "daylight" fluorescent tubes are still popular as well with growers.

Keep in mind that there is a HUGE difference between having an RGB led put out the right mixture of it's three frequencies to trick the human eye into seeing a particular color and having an LED that actually puts out that particular frequency.

If you mix red and blue to get violet, you don't really have any of the violet spectrum in there. You've just got red and blue. If you want something that will actually grow a plant, then you need to get LEDs that are meant to grow plants. Look up the term PAR and find leds that put out a lot of PAR.

Thanks everyone I found some grow oriented Led strip that seems perfect for my purpouse.

I also already have a 12v - 3A power supply to drive it.

My question is now the following:
Can I have the whole system running with only one power supply?
will this circuit FRY my Arduino? I followed an example I found online and this is the circuit I currently have drafted but I can figgure out if it will blow it or not. Or even if it works XD.

A TIP31 is totally unsuitable for this. It would need 300mA base current for a 3Amp strip, something an Arduino pin can't supply. Better use a logic level mosfet, or a relay module if you don't have to dim your strip.

If you go for a relay module, note that the Arduino can only power ONE 5volt relay module if you power the Arduino with 12volt (on the DC socket or V-in). Another option is 12volt relay modules. Leo..

Thanks Wawa, much appreaciated!

What Logic Mosfet would you recommend for the job? I have never used them before. Would the rest of the circuit work fine once I get the right one?

That's a Fritzing wire diagram, not a circuit diagram. Don't mix them up. One is a clearly readable representation of the electrical circuit, the other is mere eye candy.

The IRL540 is a good MOSFET, can easily handle the current. It goes low side (between the strip and GND).

Rovers: @Dustin, I do want to do the project and learn more about Arduino. Plus I really enjoy these diy projects.

@Saildude, I tried to look up grow light but they are all either too expensive or not suitable for the space I want to put them. This said they all seem to follow the same configuration of LED (80%red 15%blue 5%white) so I am thinking of buying some single LED and try to replicate this mix.

You only think the LEDs are expensive. Compare to grow lights.

I have a customer doing the same commercially and they pay to have custom LEDs giving the wavelengths required for maximum plant growth. No idea what they cost.

Paul

My original germination was pretty good around 75-80%. I had trouble with unexpected growth (cannabis is such a wonderful plant http://www.ilovegrowingmarijuana.com/blueberry/, and indoor growing environment proved too small. Plants which survived this growth congestion were then allowed to grow and mature outdoors. A majority (18 of 30) proved to be males, but the 12 females produced good smoke as well as the F1 generation seeds. Not sure if this was wind pollenation from native hemp, but I suspect that I failed to recognized the male traits in several plants before they were removed. Last year I used this F1 seed with good result, high germination rate, grew fewer healthy plants, and minimal seed production (F2 generation). I did master cloning techniques but lost the mother plants due to technical errors.