What circuit to use?

[arKzeRo]

Hi guys! i would like to build my own efficient grow lights for my own usage! i could just go out and buy a ready made unit of course but that would be no fun at all would it! and would be more expensive i gather!

so what i would like to know is your recommendations for a good efficient led driver circuit, I would hope to fully light at least 156 x 1 and 3 watt leds of various spectrum!

what say you all?

thanks - Jay

[Mad Scientist]

One think to keep in mind is that LED's are not created equal.

I have over two hundred LED's all around the house for supplemental lighting. I have these lamps connected in series in groups of three lamps each. I then connect these series circuits in parallel and run them with an adjustable voltage regulator (LM317) set to 9.6V. Thus each LED should only be seeing a nice safe 3.2V and in theory should last forever. Wrong!

I have had numerous failures. What I have found it that the voltage drop across these lamps is anything but consistent. If I inadvertently put together a string with widely varying voltage drops that string will eventually fail.

So for long life you will want to individually match the voltage drops so that you but only these LED's that have the same voltage drop are in series with each other.

[citfta]

A dangerous circuit.

Guys that circuit posted is a dangerous circuit to mess with. First of all even when the circuit is working like it should be all parts of that circuit are hot in reference to the neutral except for the wiring going from the R2 resistor back to the neutral. In other words if you touch any part of that circuit while it is energized you will get a nasty or even fatal shock. This circuit has been discussed on this forum before.

Secondly if the current draw of the circuit changes the output voltage will change also. So if one of the Leds fails the output voltage will go up which will then most likely cause more of the Leds to fail until the voltage goes high enough for all of them to fail. Also if the cap should fail you are going to blow all the Leds at one time.

A much better circuit is to use a transformer and reduce the voltage to a lower level which will also give you more current. Then you could use a voltage regulator like the LM317 that was suggested and set it for the right voltage for your Leds. The LM317 will adjust to changing input voltage and to changing loads so it can keep the voltage steady to protect your Leds. You could then wire all the Leds in parallel and not have to worry about matching them as long as they are all rated for the same input voltage.

Respectfully, Carroll

[plasmahunt3r]

Dangerous Circuit

I deleted the AC circuit for powering LED's. AC is dangerous and lethal. If someone wants to pursue AC powered LED's on their own, do a search for "AC POWERED LED CIRCUIT" on google and you will find a wealth of information. I use AC power source all the time for my experiments, but inexperienced testers may not be as careful as I am.

Also:
I read a few years back about NASA testing LED's as grow lights for possible extended space voyages. They found that LED's worked well, drew less power, but had one side effect. Due to the different light spectrum of LED's, Lettuce turned blue instead of green. They were using LED Traffic Lights as grow lights. Simple, off the shelf components. If some of the LED's fail on the traffic light, the other leds would keep going, so they wouldn't need to carry spare lights.