low budget build using laptop charger

[psycadelia]

I've been reading quite a bit on the site and have gotten excited about giving indoor gardening a try. I'm looking to start small in 1-2 square foot area (1'x1' to 2'x1'). I'm mostly interested in growing herbs (mint, basil, thyme, etc) and maybe moving on to leafy greens (lettuce, kale, arugula) at some point in the future. I was originally thinking of throwing together something using a bunch of 5mm LEDs, but this site has gotten me thinking about using strip lights instead.

Since I won't have very high power demands, I was hoping I could get away with a power supply I have lying around. I have a 65W power brick from an old laptop rated for 18.5V and 3.5A http://www.primelec.com/hp-compaq-65w-1 ... Be5PflKhaR. That sounds like it would give me enough power based on what I've read (30-40W per square foot), but I wanted to double check. I also wanted to check if this would act as a constant voltage driver and how that would influence which LEDs to use and their wiring.

If the power supply can give me enough power, I was hoping someone could give me a recommendation for some cheap led strips that I could buy in Canada. I was thinking of getting some EB2 strips and wiring them in parallel. However, their forward voltage seems to be 19.5v and I'm not sure my 18.5V charger would be enough. Any ideas?

[ubuntuuser]

I have thought about this too. The strips may send the PSU into thermal shut down. You might do some more research on that. Otherwise go for it but be prepared to fail and have a plan B.

[unkle_psycho]

30w per sqfoot will be overkill for herbs, probably half would be more appropriate. How long hours do you plan to run your lights per day?

There's a post here on cheap thomas research products drivers, there are a bunch of drivers in the 50-75w range that cost about 10-15$, so even if the laptop charger does not work, it shouldn't break the bank.

Bridgelux makes cheap strips, checkout the EB gen2's and the Vestas. the 1 foot strips are 3-5$

[Hydrofood]

I Definitely recommend Bridgelux Eb series strips, and Thomas Research drivers like Uncle said.

Here's a thread on alt power supplies
viewtopic.php?f=15&t=471

30w sq/ft is much much much more than you need.

[psycadelia]

Thanks for all the replies. I didn't realize I could get away with such a low wattage/inexpensive driver. The Thomas Research driver/EB strip combo looks very affordable. As far as light time goes, I was thinking 12-16 hours a day, but I would be willing play with that a bit depending on how the plants are doing. I'm ready to buy, but I was hoping someone could check my math first:

• 2x: EB Gen2 2-foot strips BXEB-L0560Z-35E2000-C-B3 (700mA, 19.5V each)

• 1x: Thomas Research Product driver LED40W-022-C1820-D(7-22V, 1.82A)

If I hooked up the strips in parallel, that would require a maximum of 1.4A and the 22V maximum of the driver would be sufficient to run the strips. Correct?

I also have a 50K potentiometer. Would this have enough resistance to work with the analog dimming feature on this LED driver?

Thanks again for all the help!

[unkle_psycho]

If you connect that driver with 2 strips in parallel, each strip should receive around 0.91A, and you should be well within the voltage range.

On page 3 of the drivers manual you can see dimming for the d & d3 models... do you know which one this is?

[psycadelia]

Thanks Unkle. The driver I selected seems to be the D rather than the D3 model, so I think it requires a current-sink wall dimmer (IP710). If that is indeed the case and I am unable to just use a 50k potentiometer, then would you suggest getting a lower current driver since I would be putting 0.91A through strips with a nominal current rating of 0.7A? It seems like they have an absolute maximum current rating of 1.4A, but will driving them at 0.91A for 16h a day hurt their lifespan significantly?

[unkle_psycho]

They are certified to 50000h at a certain temperature, I guess their max rated temp... I'd imagine its somewhere between 55-80c.

If you have any aluminium that its attached to it should easily handle 60% of max.. Without any heat sinking it would be too much. Any L or U shaped extrusion, or even some flat baking tray would be great.