# Can anyone review my plant growth circuit?

#### mw-b

Joined Mar 14, 2019
11
Hi there. I need 660 nm red light for plant growth. I don't have any experience with electronics but I have the following setup from my research on the internet:
What are the adjustments that I need to work this circuit properly?
How many resistors do I need to drop the voltage to the 9-11 V?
Should I consider heatsink without a fan?
How much amper power source should I buy?

I am planning to buy :

• Power source: 220V to 12 V adaptor (I will use basic charger adaptor)

• 10 pieces of 10 watt 9-11 V 900 mA 660 nm LEDs(Will be connected parallel) (Link)

• 12v 0.06 A fan (Will be connected serial after the LEDs) (Link)

• Aluminum Heatsink

#### djsfantasi

Joined Apr 11, 2010
6,718
Ok, reading the technical specs, each LED assembly has s forward voltage of 9-11V and will draw 900mA. Ten such packages need 9A to run.
.
First, is your power supply strong enough to supply over 9A? You also need power to run your fan and your supply should supply more than the minimum. Say a 12-15A supply.

You can’t put the fan in series with the LEDs. It needs 12V and the LEDs will take 9-11 volts from the supply, leaving only 1-3V for the fan. Wire it in parallel with the LEDs. Ask if you don’t understand why.

It’s obvious to me that each LED must be wired in parallel with the others. But how to reduce the 12V to say 9V?

Your supply (Vs) is 12V. The Vf is 9V. And the current is 0.9A. The equation for a current limiting resistor (which is actually what you do. You don’t limit volts to control LEDs as they are a current controlled device)... the equation is

R = (Vs - Vf ) / I
= (12 - 9 ) / 0.9
= 3 / 0.9
3.333Ω

Using standard resistor values, I’d use a 3.3Ω resistor.

But wait! There’s more. What size resistor do you need? ...Where size is measured in Watts.

W = I^2 * R = V * I
= ( 0.9 ) ^2 * 3.3
= 2.67W

You always want some headroom in resistor wattage ratings, so I’d be looking at a 3.3Ω 5W resistor for each LED.

#### mvas

Joined Jun 19, 2017
537
The fan will be in parallel, not serial

#### DickCappels

Joined Aug 21, 2008
6,534

The 900 ma version takes 6 to 7 volts. Using a resistor to limit the current would result in over 5 watts per LED extra dissipation. I suggest finding a constant current LED power supply that can supply the 9 amps and an extra volt or two so resistors can be placed in series to spread out the current so the lower voltage LEDs don't hog the current.

If you find a suitable 6 volt fan, it can be placed in parallel with the LEDs. If you can't find a 6 volt fan, a small separate power supply can be used to power the fan.

There may be some confusion about the terms parallel and series, so:

#### mvas

Joined Jun 19, 2017
537
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#### mw-b

Joined Mar 14, 2019
11
Instead of using a 12 Volt 9 Amp Power Supply and "Dropping" Resistors,
You can use a 900ma Constant Current Source LED Driver and connect the LED's in Series

This particular model can support 4 LED's in Series without any Current Limit Resistor
https://www.amazon.com/d/Low-Voltage-Lighting-Transformers/Constant-Waterproof-Lighting-Transformer-Aluminium/B01MR98KCE?th=1

When illuminating several identical LED's, a Constant Current Source and SERIES connected LED's is the way to go ...
Thanks. I don't know led drivers existed. What type of 900ma constant current source LED driver should buy to support 10 LEDs in series? For my calculations, I need 6-7V *10=60-70Volt. Does 60-120 Volt LED driver overpower(more than 10 Watt) the LEDs?

#### shortbus

Joined Sep 30, 2009
7,849
He had a thread over on ETO about the same thing. He still isn't addressing the big problem with the chosen LEDs. That is the fact that they are ball type connections, like a computer processor, and that they need a big heat sink for each one. But the price for them looks good.

#### Raymond Genovese

Joined Mar 5, 2016
1,658
He had a thread over on ETO about the same thing. He still isn't addressing the big problem with the chosen LEDs. That is the fact that they are ball type connections, like a computer processor, and that they need a big heat sink for each one. But the price for them looks good.
That same place/add chain sells aluminum heat sinks https://www.aliexpress.com/item/CHANZON-1W-3W-5W-LED-Aluminum-Base-Plate-PCB-Board-Heat-Sink-Substrate-20mm-Star-Kit/32682359288.html?spm=2114.10010108.1000023.3.3ac04555xHUs5j and transformers for their lights https://www.aliexpress.com/item/LED-Driver-Adapter-Light-LED-Power-Supply-Lighting-Transformer-1W-3W-5W-10W-20W-30W-36W/32756673848.html?spm=2114.10010108.1000023.2.3ac045556F6b9D at least apparently so.

#### shortbus

Joined Sep 30, 2009
7,849
But he isn't able to do the ball connections. and after buying everything needed and doing the work, the price of off the shelf grow lights is probably cheaper and they will work out of the box.

#### mvas

Joined Jun 19, 2017
537
He had a thread over on ETO about the same thing. He still isn't addressing the big problem with the chosen LEDs. That is the fact that they are ball type connections, like a computer processor, and that they need a big heat sink for each one. But the price for them looks good.
The image from the URL Link in message #1 appears to show a ( + ) Tab and a ( - ) Tab ?
https://ae01.alicdn.com/kf/HTB1JkW2RpXXXXcHaXXXq6xXFXXXh.jpg
Am I not interpreting the ( upper right ) image correctly for the 10 Watt LED ?

#### Raymond Genovese

Joined Mar 5, 2016
1,658
But he isn't able to do the ball connections. and after buying everything needed and doing the work, the price of off the shelf grow lights is probably cheaper and they will work out of the box.
I'm never afraid to ask about what I don't know. Can you explain the "ball connections"? I see from the advert "Type: Ball" https://www.aliexpress.com/item/High-Power-LED-Chip-Deep-Red-LED-660nm-Plant-Grow-Light-1W-3W-5W-10W-20W/32633843531.html?spm=2114.10010108.1000023.3.80f43b86L5pgpY

But, I confess that I am not appreciating the significance. I will say that I have purchased something like these https://www.banggood.com/9W-E27-200-LED-Grow-Light-Full-Spectrum-Indoor-RedBlue-Hydroponic-Plants-Veg-Lamp-p-1061960.html?rmmds=category&cur_warehouse=CN since I already know how to screw in a light bulb (with help).

PS:
Q: How many engineers does it take to change a light bulb?
A1: None. They are all too busy trying to design the perfect light bulb.

A2: Only the one with the instruction manual.

A3: One. But she would insist that the way she did it was distinctive.

A4: Three. One to hold the ladder, one to hold the light bulb, and the third to interpret the Japanese text.

A5: Five. One to design a nuclear-powered light bulb that never needs changing, one to figure out how to power the rest of the USA using that nuked light bulb, two to install it, and one to write the computer program that controls the wall switch.

A6: None. "According to my calculations, the problem doesn't exist."

http://www.inflection-point.com/jokes/50.htm#top

#### mw-b

Joined Mar 14, 2019
11
So my conclusion is :
1 piece 100W AC85-265V To DC 20-39V 3000mA Constant Current Power Supply()
1 piece100W 20-24 V 3000mA LED(Here)
Multiple Aluminum Heatsink which can cover the surfaces of the device (Here) (still looking for better alternatives)

Can I connect the input(AC85-265V) of the Current Power Supply to EU plug to make the product more portable? So I can carry it in my suitcase and plug it everywhere I go.

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#### mw-b

Joined Mar 14, 2019
11
If the UE Plug can supply 85 - 265 Volts AC at 100 watts then OK.

Which Heat Sink does Ali Express or Mfr suggest for your specific model 100 Watt LED ?
I don't know if this Heat Sink ( below ) is perfect match ( spacing of the 4 LED mounting screws ) for your LED or not ...
I think, your heat sink is way too small?
Thanks. Why I need 100 watts AC input? Does it just need 85 - 265 Volts AC from the cables coming from the electric socket? Also, any other idea makes it portable is important for me. because I cannot connect wires from electric socket to constant current creator everywhere I go

#### Alec_t

Joined Sep 17, 2013
11,526
I cannot connect wires from electric socket to constant current creator everywhere I go
Why not? Plugs and adapters are available for various mains outlet sockets.
Are you planning on taking your plants with you on holiday abroad?

#### mvas

Joined Jun 19, 2017
537
Thanks. Why I need 100 watts AC input? Does it just need 85 - 265 Volts AC from the cables coming from the electric socket? Also, any other idea makes it portable is important for me. because I cannot connect wires from electric socket to constant current creator everywhere I go
Portable idea ... 12 Volt ( Lithium or Sealed Lead Acid Battery ) + DC-to-AC Inverter = Portable

#### shortbus

Joined Sep 30, 2009
7,849
Am I not interpreting the ( upper right ) image correctly for the 10 Watt LED ?
I don't think you are. That is another one they sell, not the one he was linking to originally.

Can you explain the "ball connections"?
I guess I was using the wrong term, one I saw elsewhere for this type of IC. The real name is BGA , ball grid array - https://en.wikipedia.org/wiki/Ball_grid_array

#### mw-b

Joined Mar 14, 2019
11
Why not? Plugs and adapters are available for various mains outlet sockets.
Are you planning on taking your plants with you on holiday abroad?
Hehe funny. It is not just for my plant I will use it for red light theraphy

#### Audioguru

Joined Dec 20, 2007
11,249
The 6V to 7V deep red LEDs will not produce all the other colors needed for plant growth and for blue light therapy.
The other colors need 9V to 11V.

#### oz93666

Joined Sep 7, 2010
737
I consider myself a bit of an expert on this subject ... I've been using leds for plant growth for many years ... constructing my own units from chips , and dismantling and testing many units that are on the market ...

First question is why are you using 660 on it's own?? You need a balance of blue and red...

The main thing I've realized , which I've never seen covered well on the web, is efficiency !! This is very important since these lights will be on many hours .... The smaller the component chip the more efficient ....

You can buy very cheaply 100W single units for a few \$,

you won't find any cheaper per Watt, they contain the right balance of blue and red ....But the efficiency.... lumens /Watt is terrible (Don't believe any manufacturers figures for lumens output or Wattage)

The type pictured below are excellent ....

They have many well spaced small leds the efficiency is the best since the leds are well spaced and small . I remove the led plate from these units and run at a lower voltage .

Running at low voltage increases the efficiency still more by 30% !!!

The 10W chips you say you are using are not the best for efficiency , if you do already have them then run them at about 25% recommended current with a good heat sink, they will last 10 times longer and you will get 30% more light per Watt , if not enough light running at reduced current then buy more leds.... using this method no noisy fans are needed , which are expensive and waste more electricity.

Self adhesive strips are also excellent and probably the best product for most people since they are very easy to set up...

well spaced small leds in these strips allows heat to dissipate well , giving high efficiency and long life, particularly when run at reduced current (between 60 and 30% recommended current )... eBay is the best place I've found for variety and low price ....

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