Oh, one other thing, a suggestion. Put your location in your profile so it can show on the posts like mine. There are a lot of people here who can recommend local stores and what not, it may end up saving you money.

 

Mr Marsden yes heat is an issue I am in south FL. Is there maybe another brand of drivers that do what the Mean Well do but might be a lower cost? I really need to stay at the scale I am at now to match my needs. Again thanks for the time you all are taking helping me

 

You can stay at the scale you are, but my suggestion was to build something using a small bank of LEDs as a try it and see. You can always reuse the parts, but right now you don't have the experience to make an informed decision.

This thread is the closest we have come up with so far to yours.

http://forum.allaboutcircuits.com/showthread.php?t=32066

Post #28 has something I was thinking of for you. The whole thread has something for you though, I would recommend reading it.

Here is the deal, as with that thread I would design something specific, but you would build it. It is not a minor project, and if you do not want to dim the LEDs it gets much easier, as in post #3.

You tell me your needs, I will help draw a working schematic. I have no idea how you are at fabricating, some people enjoy it, some don't, and a lot are in between.

That is if you don't go with off the shelf, which is always a good option.

 

How many and what size (wattage) HPS units are you looking to replace? I'd think that many LED's is "roughly" equivalent to more than 1000 watts of HPS. Do you need that much?

Heck the power supplies are cheap.. You are looking at probably $350-500 USD on LED's..

Yes there are cheap Chinese knockoff LED drivers (constant current) out there too.. (Ebay/Deal Extreme).
Like Bill said...The biggest factor for going meanwell route (or similar knockoffs) is simplicity. You will spend MUCH more time with the circuitry for using constant voltage supplies.

Oh and don't think you can just bolt them to a flat piece of aluminum spaced 1 inch apart and be done with it. Maybe running them at 350mA but at 700mA you need a REAL heatsink with fins,etc... I needed a nice heatsink and I even added 2 small fans blowing across the LED's for extra cooling. Remember with LED's you want to keep them as cool as possible to extend life and reduce color drift over time.

 

Mr Marsden I have soldered before and I like fabing things together also. Mcgyvr from what I have seen with led grow lights the manufactures specs of led watts to hps watts are way over rated. I was using a 400 watt hps but really I think I could have used 600hps. From what I have seen on others sites of people growing with Leds even though it is not the same type of plants that I grow this number of led watts is really what I need. I have already purchase the leds and think I got a great deal 100 reds 20 blue 10 of each cool and warm white for 210.00 shipped. I was thinking of making two lights one to start with then a second later. I will use heat sinks for sure because I think I would like to run the leds at full power. Thanks again for all the time spent helping this noob

 

Ay! Full power ahead commander!

Go with post #3, and use a LM317. Put as many LEDs in series as you can, the idea is to distribute the heat as much as possible. You think you have a grasp on this, or do you have questions? I usually prefer to teach how to do something when I can, it's more fun for everyone.

 

I think I have a grasp on the drawing in post #3 of your link. The question I have is about the resistors. If I wanted to run the leds at 750mA would I just use 7 resistors after each LM317? If I drove 8 leds per LM317 I would be set with 10 LM317s. What size resistors would I need?

 

OK, if you take a 12Ω ¼W 5% resistor and use it with this circuit you will have 0.104A, and the resistor will be within its ratings. Put 7 of these resistors in parallel and you will have 0.729A. With electronics there are tolerance issues, so this is what I would go for. If you want to tweak it for exactly 0.75A you can add an 8th resistor of the appropriate value and measure it with a DVM.

The LM317 current regulator will drop around 3V, less than that and it isn't a current regulator. More that that and it get warm, very warm. One way to fight the heat is to absorb as much power elsewhere as possible, and keep it out of the current regulator. The less voltage the LM317 has to drop to regulate current the cooler it will be, and the power will be used by the LEDs, which is where we want it.

Each LED will drop a specific voltage, and the exact voltage dropped is partly a function of LED color. It is important to remember that the current is what lights the LED, but the voltage is what you have to calculate for in a long series chain. Each chain will have it's own LM317, but you can buy in quantity much cheaper over all. Radio Shack carries these parts, but they are not cheap, just handy.

Part of the reason I suggested a small build is so you could get a feel of the heat this is going to generate. You can build in sections anyhow. You may end up needing a few fans, but if everything is open to the air maybe not.

BTW, the metal tab on the top of the LM317 is tied to Out, the center pin. You want to make sure this metal tab is isolated, not in electrical contact with anything else.

 

A bit off topic here but, HPS lamps aren't the right spectrum for growing plants. The plants use mostly the blue and red ends of the light spectrum. HPS is right in the middle of what they don't need.

 

A bit off topic here but, HPS lamps aren't the right spectrum for growing plants. The plants use mostly the blue and red ends of the light spectrum. HPS is right in the middle of what they don't need.

HPS bulbs are commonly used during the flowering stage of plant life and MH used during the vegetative period.

 

Is that "commonly used" or "optimum bulb" for the flowering phase?

 

HPS is best for flowering because the spectrum of HPS is more reds and the MH has more of the blues.

 

Excellent! I know some people who are always on the watch for things that make the flowering part grow better.

 

There are techniques to use a common chunk of aluminum to mount several LM317's and have them still isolated from each other. Do you need to go over this?

The 7 12Ω resistors can be soldered together for best effect, don't just wad them together, keep some separation between them to allow air flow. Basic air cooling 101.

 

Thanks Mr Marsden I think I might do a heatsink for each LM317 unless the one block of aluminum is better. Could you point me to a photo of what the resitors should look soldered togother? The leds shipped today from Hong Kong so that is good news. The regulators I need are they LM317t per your diagarm? I need to order the regulators,resistors and some heatsinks. Thanks again for the help

 

The exact LM317 is not that important, as long as it is a high current model. They have versions designed for much less current, which for you would be a bad thing.

Separate pieces of aluminum are fine. If they don't already have heat sink fins you can buy some and bolt them on later, the fins are very effective at removing heat.

Are you going for that power supply shown earlier on the first page.

 

Use something like this...

I don't have high power LEDs drawn for my library yet, so I made do. You can insert a DVM set up to measure current anywhere in the LED chain, top, bottom, or in between. The current will be the same throughout.

Funny side note, the power supply shown is also a constant current source, but it got the point across.

 

Mr Marsden the power supply your asking about do you mean the Meanwell? I am still on the fence I would like to find a lower priced option but if that is the best way to go I guess I might go with those. I did see this on ebay what do you think I would need three I believe? http://www.ebay.com/itm/90W-LED-Dri...276?pt=LH_DefaultDomain_2&hash=item256891b824

 

Hello,

The shown model of the powersupply is designed for 2.6 A.

The driver supplies use a constant current topology and feature the following specifications:
Output voltage: 34VDC
Output current: 2.6ADC

You state the leds you used need 0.75 A.

Bertus

 

If you go that route you will not need the LM317's. That is a constant current supply, similar to what was shown by mcgyvr. Bertus spotted a problem while I was writing this post, which would seem to be a showstopper. With a little work it would be possible to split this supply 4 different ways for 650ma each.

The power supply I was referring to was in post #6. It is a constant voltage power supply, not a constant current supply.

The difference between 650ma and 750ma drive is less significant than you might believe, as LEDs are pretty nonlinear devices. You would have trouble telling the brightness apart.