[djimb]

I'm planning a new cab in which I'll be using a Mars Hydro LED panel (nominal 300w, actually pulls closer to 150) and I'm trying to decide between screw in led bulbs or a pair of DIY COB lights to supplement it. I was originally set on the bulbs, as building a fixture using 10 15w units seems like it would only cost about $60-80, but I started looking at cheap Chinese COBs and drivers on eBay, and I could conceivably get 10 100w COBs and 3 100w drivers for the same amount or less. This has led me to a few questions:

Does anyone have much experience with these cheap COBs, and could they be reliable running at roughly 33w?

I'm thinking running 3 COBs per driver (wired in parallel?) might be sufficently under powered to be reliable, and two fixtures built like this would leave me with enough spares to replace anything that burns out.

If that configuration does work, would it run cool enough to be able to use similarly cheap passive heatsinks, or would they need fans?

Would it be better to use more COBs at lower wattage?

Would it be better to stick with LED bulbs?

Ideally, in another year or so I'd replace this setup with either better COBs or a CMH (or both?), so this won't be a permanent solution. I'm just trying to keep initial costs on the low end while still getting better results than I've had with the Mars Hydro panel alone.

Thanks!

[Koondense]

You're going the right way, the chinese cheap cobs are not good but can be better than household leds when driven softly. I'd suggest around 30-40% of max load.
CMH is obviously much better.

Cheers

[DJXX]

Originally Posted by djimb

I'm planning a new cab in which I'll be using a Mars Hydro LED panel (nominal 300w, actually pulls closer to 150) and I'm trying to decide between screw in led bulbs or a pair of DIY COB lights to supplement it. I was originally set on the bulbs, as building a fixture using 10 15w units seems like it would only cost about $60-80, but I started looking at cheap Chinese COBs and drivers on eBay, and I could conceivably get 10 100w COBs and 3 100w drivers for the same amount or less. This has led me to a few questions:

Does anyone have much experience with these cheap COBs, and could they be reliable running at roughly 33w?

I'm thinking running 3 COBs per driver (wired in parallel?) might be sufficently under powered to be reliable, and two fixtures built like this would leave me with enough spares to replace anything that burns out.

If that configuration does work, would it run cool enough to be able to use similarly cheap passive heatsinks, or would they need fans?

Would it be better to use more COBs at lower wattage?

Would it be better to stick with LED bulbs?

Ideally, in another year or so I'd replace this setup with either better COBs or a CMH (or both?), so this won't be a permanent solution. I'm just trying to keep initial costs on the low end while still getting better results than I've had with the Mars Hydro panel alone.

Thanks!

if you see the pics below these are Bigeye LEDs and they needed some cobs replaced, so i bought the 100 watt chinese cobs and at 7.99 each they do pretty good, if you got the money i would buy Cree CXB3590 at $32, using the same drivers, but at the 7.99 price if you are ok with changing them, those work pretty good, they start goin out a row at a time after bout 2 yrs use....also look on ebay, they have really cheap cob led grow fixtures and verses buy the parts, just buy a fixture already put together....another thing you might check out is DIY Quantum Boards, check out Lapides thread on those, they are pullin some insane yields with those cob strips...and they are pretty simple builds..DJXX

[Killkingkong]

I built this light for just over $50 using cheap china cobs, cheap china heatsink and a cheap china 50w driver.





I'd recommend spending the extra money on the LEDs, the cheap (300mmx140mm) heatsink and driver are fine. The cheap one was the first light I made with the cheap $14 heatsinks from china/ebay. The higher quality lights come from digikey. they were made by lumiled, but I wish I saw the samsung ones that are thinner ( you can fit 6 instead of 5 on the heatsink). the samsung ones are 11v, so I would run them 3 series 2 paralell to get to 33v which is in the range i currently use.

[DJXX]

sweet cking you out...you are way more advanced than i am...did you ck out Lapides DIY Quantum Boards...not near as cheap as you have done, but really insane yields done with them..DJXX

[Killkingkong]

Originally Posted by DJXX

sweet cking you out...you are way more advanced than i am...did you ck out Lapides DIY Quantum Boards...not near as cheap as you have done, but really insane yields done with them..DJXX

He's how I found out about the strip cob lights. I don't post much anymore, but I keep up with the latest technology and they're way more efficient and spread the light out much better. I just applied what he did to my cheap style. I was mostly using those square LED cobs before, but they put all the light in a single spot. I've tried all kinds of LEDs you can think of, those strips are the best purchase you can make for the money. BTW, the strip lights don't require soldering at all. Either screw or glue them down, then push high quality wires into the slots.

[djimb]

Thanks for all the feedback, everyone!

Killkingkong, that looks about like what I was planning on, only I'd split it into two fixtures to hang on either side of the Mars Hydro panel. I was thinking of doing 3-4 per 100w driver. I'll look into those Samsung strips, too.

DJXX, I'll definitely look into the quantums, too. I like the idea of strip LEDs for more even coverage. I've also looked at the Sol Strips that ReikoX is using over in the micro grow forum. Those seem pretty affordable save for the drivers they sell.

Koondense, thanks for the tip about running them light. I figured pushing them at the rated wattage would only burn them out.

[bsgospel]

Originally Posted by Killkingkong

He's how I found out about the strip cob lights. I don't post much anymore, but I keep up with the latest technology and they're way more efficient and spread the light out much better. I just applied what he did to my cheap style. I was mostly using those square LED cobs before, but they put all the light in a single spot. I've tried all kinds of LEDs you can think of, those strips are the best purchase you can make for the money. BTW, the strip lights don't require soldering at all. Either screw or glue them down, then push high quality wires into the slots.

So the cheap chinese panel was ~$50- how much would you estimate the samsung strip panel you show costs? My guess would be ~$120 from what I've been seeing online.

[Killkingkong]

Originally Posted by bsgospel

So the cheap chinese panel was ~$50- how much would you estimate the samsung strip panel you show costs? My guess would be ~$120 from what I've been seeing online.

The last time I bought cheap cobs (~2-3 years ago) a 10 pack cost me $27 free shipping. The samsung quantum board light strips that fit on a 300mm long heatsink cost $8/each and you can fit 6 of them on there, so only $21 more (before shipping cost) for much much better quality and slight spread than cheap cobs or screw in LEDs. However on digikey you get a price break at 10. so you can get 12 light strips for ~$80 (not including shipping) and build 2 of them for ~$120.

Parts List:
LED: https://www.digikey.com/product-deta...282-ND/7562240

Heatsink: https://www.ebay.com/sch/i.html?_fro...tsink&_sacat=0

Various Wattage Drivers: https://www.ebay.com/itm/10W-20W-30W...-/192014536760

End Result:

Closet Light being run at 100w, so I went overkill with fans. I'm overdriving these lights a ton, but the results are great.




PC Light being run at 50w. side fans blowing hot air toward the exhaust.

[bsgospel]

*high five* Thanks for sharing! Something in this vein will be my next project. Sorry for hijacking OP. Hope it helped you too!