# How do I power my 50 red 3-watt LED's and my 20 blue 3-watt LED's without using resistors to make a panel?? PLEASE HELP

I am no electrician and am having no luck searching the internet on how to power the LEDs.
I am trying to build a grow light with 50 - 3 watt Red LED lights and 20 - 3 watt BLUE LED lights. The total power consumed would be 210 watts.

Specs for Blue lights:
DC Forward Voltage (VF): 3.2 Vdc ~ 4.0 Vdc
DC Forward Current (IF): Typ 650mA

Specs for Red lights:
DC Forward Voltage (VF): 2.0 ~ 2.8 Vdc
DC Forward Current (IF): Typ 650mA

I know a lot of things on the internet call for resistors but for this project, resistors would give off far too much heat. I know that an LED driver can be used in place of the resistors, but I don't know anything about voltage or amps.
I have found a few 200W LED drivers that connect to an outlet and convert the power to a 24V DC, which is usable by LED's.

I just don't know if that's all I have to do: connect the driver to the LEDs in a parallel circuit.
Actually, I don't know how to find the Constant Current Module that I need at all.

PLEASE HELP ME!

mad-led-man2 years ago
your ansew to amps

1000 milliamps = 1 amp

if you have 20 x 3w led diod at 700ma we work this out

700 x 20 = 14000 milliamps then divide by 1000 = 14 amps

I'm making the best grow light on the market 40 x 3w 700ma leds

so that's 700ma x 40 lights = 28000 milliamps divide by 1000 = 28 amps so i need a 360w 30amp led driver to make this work even though it only uses 240w in theory .
so if your ring main is 32 amps you'll need to rewire a new circuit for these lights as itll draw to much amps.
lense angles. any led lense over 90 degrees will not grow very well. the lights i use is 60 degrees and 90 degrees for best results.
any led under 700ma will not dense buds on plants they dont tell you this.
if any one has a question ill be glad to help i make the best grow lights to order

1 year ago
40x 3w = 120w what do you mean your only using 240w ???
GoonyLex1 year ago
I just did a very similar setup and will be posting an instructables about it. To answer your question I personally used 5 of these drivers . When you buy 5 they drop the price from 14 dollars to 12 so it come to about 60\$ for 60 LEDs.
Here is the link: http://dx.com/p/waterproof-670ma-36w-power-constant-current-source-led-driver-85-265v-42906?item=1
This way you can add 5 switches and have individual controls for every 12 led.
This is good for growing and flowering cycles. I would also install a thermal cutoff just in case. The nice thing about these drivers is they are waterproof so you don't have to worry about humidity effecting electrical circuits.
1 year ago
hi Goonylex. i have a question about led drivers. could you use one led driver to drive more the one led? will say the driver has an out put of 12vdc and say 3amp, and I have 3 leds that run on 12vdc and are 1 amp each.
or use 4 ,3watt leds in series+12vdc [i think they were 3vdc ea.] and have 3 sets of those.
tks
John
iceng3 years ago
If you put all the 50 Red LEDs and the 20 Blue LEDs in series they will take from 200 VDC to 256 VDC.to lite up assuming you know how to cool them.
Next rectify the AC 120V Line with a 220 uF electrolytic capacitor for 170 VDC min...
Now add a 48 V 750ma transformer in series with the AC line and this rectifies to 268 VDC.max.
Add a 100 ohm series resistor 50 watt (or 10 5watt 10 ohm in series ) if the LED fwd is 200V Low.
if the LEDs fwd is 256V high, add a 12 ohm resistor 5 watt in series..

If I did this correctly you need a 300V 2A DC Bridge, a Radio-Shack 120/48V 750ma transformer, one power resistor, all your LEDs, and heatsinks, a 220uF 300VDC capacitor, and a 1amp slow blow fuse to grow your plants from line power.

I would check the current flow and adjust to the desired 650 ma by changing the resistance one resistance.
3 years ago
You really want more resistance than that, because a resistor <> constant current source, unless its value is >>higher than the load resistance.

Steve
3 years ago
Not to mention load resistance is varied with temperature, which 200 watts of power tends to ...vary.
frollard3 years ago
To echo what steve says, do NOT attempt to run 200 watts of leds with resistors. you'll just end up sad, and on fire.

You need a product like
http://www.dealextreme.com/p/3-0a-100w-power-constant-current-source-led-driver-85-265v-47306 100 watt
and/or
http://www.dealextreme.com/p/1-6a-50w-power-constant-current-source-led-driver-85-265v-47304 50 watt
and/or
http://www.dealextreme.com/p/1-7a-60w-power-constant-current-source-led-driver-85-265v-47305 60

There are many many options for drivers, but two of these will power your array quite happily.

Also consider - you'll need to bolt your leds to a MASSIVE heatsink, or a small heatsink individually to prevent the aforementioned fire.
You need some combination of series and parallel to absorb that power as evenly as possible.

Since there's an uneven number of red vs blue lights, you probably want dissimilar drivers...to match the totals of each and keep things simple.

"Specs for Blue lights: x20
DC Forward Voltage (VF): 3.2 Vdc ~ 4.0 Vdc
DC Forward Current (IF): Typ 650mA
Let`s say 3.5 volts each as a safe number
Total = 3.5 x .65 x 20 = 45.5

Specs for Red lights: x50 <<DC Forward Voltage (VF): 2.0 ~ 2.8 Vdc
DC Forward Current (IF): Typ 650mA
Let`s say 2.5v to be in the middle again...
Total = 2.5 x 0.65 x 50 = 97.5 watts

I'm trying to do the maths, and they don't add up - can you confirm your numbers? Every bit of data you have helps.
ammakrom (author)  frollard3 years ago
I'm sorry, I think I may have given you some faulty data; here is the exact data from the page. 3W Super bright Red LED and Blue LED. Blue=100 lumen Red= 80 lumen.

Red (50 diodes)

Forward Voltage (1.8-2.4)
Wavelength if 750mA (620-630)
MCD if 750mA (160,000-200,000)
Reverse Current(uA) Vr=5V ---> Max (10)

Blue (20 diodes)

Forward Voltage (3-3.2)
Wavelength if 750mA (460-465)
MCD if 750mA (250,000-270,000)
Reverse Current(uA) Vr=5V ---> Max (10)

Does that help?
3 years ago
a little -- but the numbers still don't add up. At absolute maximum voltage (which should be around 2.5 for red) the red leds use 2.5*.75 = ~1.9 watts.

Blue 3.2*.75 = 2.4 watts.

I'd be asking the seller for an official datasheet for those. Often the numbers are inflated to make the product look better and you might burn them out driving them at those currents. It won't hurt them to be under-driven however, in fact it's generally safer.
ammakrom (author)  frollard3 years ago
Ehhhh, I hope I didn't just get ripped off...
So what should I do to power them? I e-mailed the ebay company and they guarantee to get back with you in under 2 business days; I asked for the datasheet.

How much power should I feed them if the values you have are correct?

Thank both of you guys for helping me, btw.
3 years ago
It just means they're exaggerating the wattage it seems - a 3 watt led should draw over an amp at standard voltages for a red...

They might be under-driving them to make them last longer. Trouble is, most constant current supplies can only work within a 'window' of voltages to ensure the correct amperage is reached. When you get a reply, let us know, we'll be happy to help (or someone will)
ammakrom (author)  frollard3 years ago
I pulled this off of the specs from a similar item that looks very close to what I ordered, except the ones i ordered had a higher average forwaward voltage. These specs are for a different "3-watt" red led.

What do you think?

Electrical-Optical Characteristic (Ta=25oC)

Item Conditions Min. Typ. Max.. Unit
Forward Voltage VF If=700mA 1.8 2.0 2.2 V
Dominant Wavelength λp IF=700mA 625 / 635 nm
Luminous Intensity IV IF=700mA / 85 100 lm
50% Power Angle 2θ1/2 IF=700mA / 140 / degree
Note:

Absolute maximum ratings Ta=25℃
Tolerance of measurement of forward voltage±0.1V
Tolerance of measurement of peak Wavelength ±100K
Tolernce of measurement of luminous intensity±15%
Absolute Maximum Ratings (Ta = 25oC)

Item Symbol Absolute Max. Rating Unit
Power Dissipation PD 3000 mW
Forward Current (DC) IF 700 mA
Peak Forward Current IFP 1000 mA
Reverse Voltage VR 10 V
Operation Temperature Topr -40~100oC /
Storage Temperature Tstg -40~120oC /
Lead Soldering Temperature Tsol Max. 260oC for 5 sec.
3 years ago
I highly recommend reading http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/

It explains some of the math, and a few solutions.

As for driving 50 of them, you still need a big driver, but this helps it make sense.
ammakrom (author)  frollard3 years ago
Also, each diode has a heatsink built on to the back, here's the link for the diodes I bought ---> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120646862871&ssPageName=STRK:MEWNX:IT#ht_6042wt_1111
3 years ago
No, each LED has a panel that you have to CLAMP to a heatsink. The star tab basically isolates the electricals from the heatsink.

The usual thing is a piece of Extruded aluminium heatsink.
steveastrouk3 years ago
Don't forget the LEDs will ALSO dissipate power ....210W of it to be exact, so the contribution of the control for it may be pretty well negligible. These big LED's need a better control than a resistor anyway.

Look online for "200W LED driver" gets quite a few hits.

Steve
ammakrom (author)  steveastrouk3 years ago
Oh okay good. That's what I've been looking at, I just wasn't for sure that 200w LED driver is what I needed. I didn't want to go buy one and then be up the creek and have the wrong thing. lol

So If I put the driver on a panel, connect all of the LEDs in a parallel circuit, will the lights be at their optimal power? The only thing I know about is Watts. I was just going on the thought that if I have 70 3-watt leds, then I need a 200-watt driver.

Do I need any resistors or any other type of converter to connect the driver and the LEDs to the power outlet? The outlet is usually 120v, right? I don't want to blow all the diodes when I plug it up or have the driver overheat and have a big mess.

If possible, someone who has a few minutes to spare, could anyone explain or draw out a simple diagram of how I'd need to wire everything together?

Sorry I'm so helpless... lol
3 years ago
power leds like one thing, constant current within their voltage RANGE. ohms law states the current flowing through a load is proportional to the voltage divided by the resistance.. The thing is, the resistance changes with temperature (among a few other factors) -- so you need to regulate the current with a driver, meaning the voltage may float around a bit so long as the current remains the same.