24 Watt LED Grow Light With Brightness Control

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Introduction: 24 Watt LED Grow Light With Brightness Control

About: Autistic person who's interests include utility cycling, recreational cycling, cycling safety, electronics, gardening, Arduino, and LEDs.

Food growing is one of my favourite hobbies because I am a big fan of organic foods and healthy eating. This Instructable will show you how to build an LED grow light with red/blue brightness controls to suit your growing needs and allow you to experiment.

LED grow lights are a relatively new method of growing plants. They are very efficient because they produce only the wavelengths needed for photosynthesis and very little heat. Most grow lights produce a lot of green light, which is reflected by the leaves. It costs less than $40 to make and doesn't cost much to run. Since it produces little heat, it's safer for your plants.

In this Instructable you will learn:

  • How the colour of light sources affects the growth rate of plants
  • How to make a grow light system with high power LEDs, PC heatsink, and other electronic components
  • Why it's crucial to drive high powered LEDs properly
  • Why a light meter is essential when designing a grow light system
  • How LED performance can be optimized
  • How to create an LED grow light system so that plants receive more light

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Step 1: Things Needed

Greenhouse

  • Aluminum foil
  • Large box
  • Plastic board

Grow lamp

  • 2 x 3W royal blue LED (445nm)
  • 6 x 3W deep red LED (660 nm)
  • Heatsink with fan
  • Thermal paste
  • Epoxy
  • Solder (lead-free when growing edibles)

Note: You can get LEDs at e-Bay for as little as $2 each when you purchase them wholesale.

LED Driver

  • 1A fuse with clips
  • Resistors (0.33, 0.56, 1, and 100k ohm)
  • N-channel MOSFET (e.g. IRF540N) with heatsink
  • General-purpose NPN transistor (e.g. 2N3904)
  • Enclosure
  • Switches
  • 1A adapters (see below)
  • DC adapter socket
  • Wires

Finding the right voltage adapter
You can find adapters at a low price at used computer stores, second-hand stores, electronic stores, and eBay.

Tools that you may need:

  • Multimeter capable of measuring several amps
  • Light meter
  • Electric timer

Step 2: Grow Light

Use a Current Regulator
High power LEDs require a constant current source so that they last a long time. That means they'll need an LED driver. I used the MOSFET regulator below. Before soldering, you should test the circuit on a breadboard. The second diagram included the brightness settings. I used an on-off-on two-pole switch.

Mount to a Heatsink
These LEDs also require a heatsink, or they will get extremely hot. I attached them with epoxy. The heatsink I used can hold a maximum of 8 LEDs. You can strain relief the wires with hot glue. With the heatsink fan, the heatsink doesn't get hot.

Tie the Wires Together

Step 3: Housing for Plants

I used an enclosure to hold the grow light and increase the lighting with aluminum foil.

Step 4: Cost and Power Consumption

Watts Used by the System (High Setting)
Red LEDs: 14.55V x 0.68A = 9.89W
Red LEDs with driver:16.13V x 0.68A 10.97W
Blue LEDs: 6.98V x 0.64A = 4.47W
Blue LEDs with driver: 10.24V x 0.64A = 6.55W

Watts used by grow light: 17.5 W*

Cost to run the grow light: 17.5W x (1kW/1000kW) x $0.10 per kWh x 16 hours x 365 days per year = $10.22 per year

Watts Used by System (Low Setting)
Red LEDs: 13.13V x 0.32A = 4.20W
Red LEDs with driver = 16.19V x 0.32A = 5.18W
Blue LEDs: 6.28V x 0.31A = 1.95W
Blue LEDs with driver:10.64V x 0.31A = 3.30W

Watts used by grow light: 8.48 W*

Cost to run the grow light: 8.48W x (1kW/1000kW) x $0.10 per kWh x 16 hours x 365 days per year = $4.95 per year
*Power supplies are excluded.

For conventional 250W grow lights, the cost is about $146 with similar schedules.

Measuring Power Consumption
The power consumption can be calculated by measuring the voltage across the circuit and measuring the current across the switch while the LEDs are off and solving the equation:
P=IV.

If you want to know the LED's voltage drop, measure the voltage across the LED's. The current across the LED(s) is similar to the current across the entire circuit because the resistance of R1 is very high. Note that the power dissipated by LEDs is not always equal to the labelled voltage.

Cost of the Grow Light
LEDs: $16
MOSFET with heatsink: $7
NPN transistors (per package): $1
Resistors (4 packs): $2
PCB: $0.75
16V laptop charger: Free
12V adapter: $3
9V adapter: $3
Switches: $2.50
Fuses: $0.60
Fuse clips: $1

Total: $37.30

Step 5: How Much Light Does This Put Out?

Measurement of Light Output
You can use a horticultural light meter to measure the light output objectively in the useful range.

Ways to Increase Performance
Use lenses
Use low footprint LEDs to pack more power into the same space.

Step 6: Other Tips

Adjust Length of Day
With an electric timer, you can actually "change the seasons" by adjusting the length of the dark period. Cool-season vegetables prefer approximately 12 hours of sunlight. Warm-season plants like roots and most fruits and flowers require longer days, like 16 hours. Please feel free to experiment.

Use a Heating Mat
Since grow LEDs produce very little heat, heating mats are useful in cold conditions.

Use Far Red (730 nm) LEDs
If you can find far-red LEDs, you can try using them to control flowering. When exposed to far-red at the end of the day, plants would think they were to red light for a shorter period than actual.

Step 7: Results With Photos

Step 8: Results II

Make It Real Challenge

Participated in the
Make It Real Challenge

Education Contest

Participated in the
Education Contest

1 Person Made This Project!

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36 Discussions

0
Rorschach72
Rorschach72

3 years ago

What is "overhead voltage"? I have tried searching the term and can't
find a definition anywhere. Google doesn't even recognize the term for
some reason and only gives results involving overhead power lines.

0
xsizhe
xsizhe

5 years ago on Introduction

How do I calculate the current passing through the LED? for example,

Watts Used by the System (High Setting)

Red LEDs: 14.55V x 0.68A = 9.89W
Red LEDs with driver:16.13V x 0.68A 10.97W
Blue LEDs: 6.98V x 0.64A = 4.47W
Blue LEDs with driver: 10.24V x 0.64A = 6.55W

why the current for Red LED is 0.68 and for blue LED is 0.64

0
uncledj
uncledj

Reply 4 years ago on Introduction

Me, confuse too, 3W red/blue led consume 600-700 mA from datasheet. math does not match

0
lionelbond
lionelbond

5 years ago on Introduction

Not only the instructable but the conversation that it is going on down here. Excelent!!!! Thanks Everyone!

0
mrdudej
mrdudej

7 years ago on Introduction

What can you suggest for growing a citrus tree indoors during the late fall to early spring?
Is 24 Watts enough and is your current configuration acceptable?

0
hanlin_y
hanlin_y

Reply 7 years ago on Introduction

Citrus trees require full sun. In full sun, my light meter reads G to H but you will need lenses for similar lighting more than a few inches from the LEDs. Narrow angle lenses provide greater light penetration. For a small area, 24 watts might be enough. What kind of citrus tree are you growing?

0
mrdudej
mrdudej

Reply 7 years ago on Introduction

I have one meyer lemon tree which will grow its first fruit this winter and a persian lime that hasn't flowered yet despite being taller than the lemon

0
ylinggarjati
ylinggarjati

6 years ago on Introduction

can u give me ebay address to buy LED 3W royal blue LED (445nm) and 3W deep red LED (660 nm)?

0
hanlin_y
hanlin_y

Reply 6 years ago on Introduction

Sure no problem.
Royal blue LED:
http://www.ebay.com/sch/i.html?_odkw=royal+blue+led+3w&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.Xroyal+blue+led+3w+445.TRS0&_nkw=royal+blue+led+3w+445&_sacat=0

Deep red LED:
http://www.ebay.com/sch/i.html?_odkw=royal+blue+led+3w+445&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR9.TRC1.A0.Xdeep+red+3w+LED.TRS0&_nkw=deep+red+3w+LED&_sacat=0

0
660
660

7 years ago on Introduction

Interesting review. Respect. But ... This is not the full range! My plants live a long time. They do not see the light from the window - only the LED. I use the 3 wavelengths, 445, 620 and 660 Nm. Important - the right combination of range, or a great result for the start and the finish of the collapse. You can use different combinations of range and get different results. I grow pelargonium, a caprice plant is very sensitive. However, 90% I was able to give the right light for the plants.
If you are interested, I can show my picture plants that all life under the LEDs.

0
Alex 77
Alex 77

7 years ago on Introduction

Why did you use 4 deep red (660nm?) + 2 bright red (630nm?)?

0
bobking144
bobking144

8 years ago on Introduction

does anyone know why when you use a power supply with higher or low voltage why the amps go up with higher voltage and down with lower voltage. It just makes it hard to get the amperage right.

0
bobking144
bobking144

Reply 8 years ago on Introduction

your right I breadboard it and it works fine somehow I have been making it wrong.

0
hanlin_y
hanlin_y

Reply 8 years ago on Introduction

In my grow light, changing the voltage had little or no effect on the current. You may want to check if you wired it correctly. I tested the circuit with a breadboard and measured the current before soldering.

0
hanlin_y
hanlin_y

Reply 8 years ago on Introduction

The N-channel MOSFET used here has a different pin configuration from that of the NPN transistor.

TO-220.jpg
0
cidly24
cidly24

8 years ago on Introduction

do you know Apollo led grow lights from cidly? i think it is better than this.

0
bobking144
bobking144

8 years ago on Introduction

Thank you hanlin_y for the help. one more question in the schematic the led are wired in series would it be ok to do the led in parallel?
Thanks.