Hi Bill, I've measured the voltage drop and its roughly 2.2v.
(should I be concerned that the leds barely lit up?)

I'm not sure if the 24v power supply is regulated or not, its got a bunch of symbols.. would one of those indicate it?

 

With a 1k resistor limiting the current to 6.7mA from a new 9V battery the LED should be fairly bright. With a 24V power supply the lED will have a current of about 22ma and will be bright.
If you used a new 3V battery then the current is only 0.7mA and then the LED will be barely lit up.

 

How about the blue? I suspected 2.2V for the red, it is pretty close to the norm. I'm betting the blue is around 3.6V, also the norm.

 

yes the blues are 3.6v.

 

My ordinary red LEDs are typically 1.7V like this:

 

Show me the source posting for the 24VDC. I'll take a look and see what I can see.

I don't like this thought since you new, but we could make some solid state current regulators. This should be a case of last resort, if the supply is not regulated.

Total Current = 0.38A

 

My ordinary red LEDs are typically 1.7V like this:

Those are old LEDs (no comment about your age).

I prefer the older models, but you can't get them as easily. They are less efficient (bright). I don't think they make them anymore.

Part of the reason I like them more is for things like the LED bargraph in my article. That and it takes less battery voltage.

**********

Looking at the datasheet they show up as new. I didn't think they made that style anymore. Most the ones I've bought lately are 2.2V Vf.

 

here's a pic of the power supply...

 

Hello,

As the powersupply is "only" 3 VA, the max current will be 3 / 24 = 0.125 A = 125 mA.
This will probably be not enough for the leds.

Bertus

 

You are going to want something more like a printer or a laptop power supply.

They will give you the amperage you require.

Just a question.. Is this a grow light?

If so, there will be a few changes you may wanna throw in. It will not change the design at all.

 

Hey all,

I'm getting kind of confused because I said i'm one of my previous replys that the 24v was 3 VA and Bill asked if that as the one I wanted to use...

I do have a laptop psu thats 12v 3.8A... But I may just buy a psu if none of those are suitable.

And yes Retched it is a grow light...What changes where you thinking of?

 

And I thought I had explained why we couldn't use anything less than 20VA. You need to think in amps, I've gone over this in great detail.

Last part of the conversation you were talking about buying a power supply unit. The units you have just don't have enough juice, read the previous posts.

To repeat again, higher voltages are more efficient. They have fewer LED legs, and each leg is a bit more efficient than a lower voltage power supply would use.

You will need 2A or more (more is better) for a 12V power supply. You can use less than an amp for 24V. Please stop using the VA rating, it doesn't apply well and confuses the issue. Max current is what matters.

I've shown how to do this with 24V. I've also shown how to do this with 12V before the total numbers changed. I'll show how to match 12V to the current numbers.

I can help, but you're the one doing the work. If you buy a power supply (like the 12V shown) we'll need full information on it. If you buy a power supply 24VDC is better, fewer parts, more efficiency. If you buy a unregulated power supply you need to measure the voltages, and you can't test sections like you could with a regulated version.

 

ok, how about this one:

50W 24V 2.1A Regulated Switching Power supply

here's the link on ebay:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280403359248&ssPageName=STRK:MEWAX:IT

 

That would be good, use the 24V layout I showed on post #26. I added some info on that post, it will use 0.38A. Since you need to double that for reliability, a 1A supply is the minimum.

I had just finished the 12V layout, so I will post it as a basis of comparison.

Total Current = 1.03 amps

 

You will want to exchange an orange for one of the reds. Following Bills pattern, add an orange like this:

For photosynthesis, your major wavelengths are covered by the red and blues. During vegitation cycles, plants "look" for seasonal changes to transistion into flowering cycles. The orange will balance out the equation and allow the plant to follow natural cycleing without "confusing" them into a one season year.

Some plants will not transition into flowering cycles without an "outside" influence.

 

ok... so to try and simplify the wireing I have come up with this...

7 rows of blue and red (7 red + 6 Blue)
6 Rows of Red (6 Red + 7 Red)
1 Row Blue (6 Blue)

That would use 127 Reds and 48 Blues

See diagram below:


Would that work the same??

 

Yes, that looks good. I ran through the numbers, it works.

Orange is typically similar to red in voltage drop.

 

Thats great!! I can get started...

Just one other thing, what resistor would I need for the fan??

btw, thanks for the input Retched, But I was reading that seasons can be simulated simply by the timers.

 

Heh, I forgot about the fan. A 150Ω or a 180Ω 2 watt resistor would work (I calculated it is 171.4Ω at 0.07A and 12V). You could also use two of these fans and put them in series. Or you could get a 7812 voltage regulator and a 0.1µF capacitor and power the fan with it off the 24V. The regulator will get quite warm, make sure it is in the open (a small heat sink wouldn't hurt).

 

btw, thanks for the input Retched, But I was reading that seasons can be simulated simply by the timers.

Not all true. Some plants change there cycles from the changes in light times, however, you can shock you plants by not offering the orange. The plants expect the orange to be there. It is obviously your call.

The reason time cycling works with white lights, is because all of the colors are present, but the only ones that matter are red, blue, and orange.