LED Driver for 60 x 3 Watt LED's? ( DIY Grow Light )

[lilsammy]

Hi all,

This is my first post I could of asked on another forum but I thought I would get more educated responses if I asked here.

I am currently building a DIY LED grow panel for testing the difference in growth rate between LED grow lighting and HPS lighting.

So on my shopping list so far I have

20 x 3 Watt 445nm LED
DC Forward Voltage 3.8V - 4.0V
DC Forward Current 700mA

40 x 3 Watt 660nm LED
DC Forward Voltage 2.7V - 3.0V
DC Forward Current 750mA

My question is I am trying to do this on a budget so far I managed to pick the LED's up for $108 (£66).

I am now at the stage where I need to get a driver for these I have been looking online and to be honest the LED driver seems to be very expensive when compared to the cost of the LED's is there any way to make my own LED Driver that would cost less than what I have found online?

I am very new to the whole theory side of electrics I mean I can wire appliances and solder componentes to circut boards etc I just haven't had to deal with sort of thing before so if you could "dumb down" or explain any technical response that would be good.

Also I live in the UK so the voltage in my house is 240V~

Thanks All.

 

[mister_rf]

In order to start implementing such a very low budget project, do you have access to some cheap/old/unused power supplies ? :-D

 

[lilsammy]

I have some 300Watt desktop PSU's I have heard people using laptop power supplies for this type of project but I am not sure how to go about it.

I was wandering how do you calculate how much power you need etc and how to give the right amount of power. I mean when I calculate the power needs of the LED's (see below) it works out as alot of power will I just need to wire them up in series so they use the right amount? but then what happens if one of the LED's in the series dies?

Blue LED's
60 Watts
78 Volts
14000 mA
14 Amps

Red LED's
120 Watts
112 Volts
30000 mA
30 Amps

 

[mister_rf]

It’s more efficient to connect the LED’s in series, but that’s true, there’s no backup for that situation.
For a classical series connection: LED’s + resistors, the amount of total power needed is the sum of the LED’s power plus the power dissipated in the limiting resistors.

---------- Post added at 11:32 ---------- Previous post was at 11:14 ----------

So, you may start connecting the LED series to accommodate the available power supply and obtained set of strings to be combined later in parallel. The resistor value in each string is computed by subtracting the LED’s voltage drop from the supply voltage and then dividing by the desired LED operating current. Usually, for a SMPS need to consider a minimum 1.5-3V voltage drop on the power resistor and the rest of the voltage to cover LED’s, trying to minimize limiting resistors wasted energy.

 

[lilsammy]

Ok this is a diagram I knocked up of how I intented to lay the LED's out but with the calculations for each series done.

So now I just need to find resistors that will take my input voltage from the house socket down to these levels?

Ok so I will need to read your post a few times before I get what your saying but thanks for explianing it to me.

 

[mister_rf]

In practice it doesn’t matter how the physical LED’s layout was designed, the electrical connections may be completely different for an operational circuit.
The main question still active: have you any SMPS available for this project ? (the total combined power rating> 200W)