Current rating of COB?

[bobulak]

Hi. Im looking to build a DIY COB grow light and Im a little confused. The cob im looking at states that the voltage and current requirements are 30 - 34V and 1500 mA for a 50w cob. Does that mean that 1500 mA is the max current or the operating current of the COB. Could I run a COB like that with a led driver that provides 1400mA constant current? Thanks

 

[Stunned]

@Old Salt
Would be a good person to offer advice on this

 

[Old Salt]

Without knowing the part number of your COBs so I can look up the specifications, I can't answer your question.

I'm using Citizen CLU048-1216s with a maximum drive current of 3680mA, and voltage of 36.8VDC. Looking at the specifications, all the performance measurements for this COB are taken at a constant current level of 1440mA. I have four in series on a Meanwell HLG-240H-1750B. Although the COBs are rated at 135W each, I'm running them at about 40W. With that driver I can go from about 2W, up to 68W each. Note that the efficiacy (lumens/watt) drops as the power is increased.

As a guess, I'd say your COBs should be run at a maximum of about 20W, so a 700mA driver is called for.

 

[bobulak]

Thanks for the info. Quick question . Why do some cob chips have a current range listed in their data sheets and some have fixed forward current values?

 

[Old Salt]

It depends on how the manufacturer wants to present the data. Citizen provides the maximum current, and the current where they measured the performance their COBs. To find out the COB's performance under other conditions, you need to consult the various graphs they provide.

 

[bobulak]

Thanks Old Salt. Im confused as to why the Chinese chip sellers insist that if the forward current says 3000ma then the chip needs 3000ma to run and that the chip wont run with any less than that amount of current. There are even a few sellers that sell a constant current driver with a chip that is powered at its max current rating. Why would they do this if running it at max current will burn out the chip?

 

[Old Salt]

It could very well be the sellers have little to no knowledge of electronics. If you want to use those chips, I'd get one or two, and also get a cheap regulated power supply to test them.

 

[bluter]

Thanks Old Salt. Im confused as to why the Chinese chip sellers insist that if the forward current says 3000ma then the chip needs 3000ma to run and that the chip wont run with any less than that amount of current. There are even a few sellers that sell a constant current driver with a chip that is powered at its max current rating. Why would they do this if running it at max current will burn out the chip?

cob rigs can be set up either constant current or constant voltage. some cheap chips and and cheap chip makers have a bias to one or the other. the goods ones can be run either way depending on how comfy you are with the different wiring.

 

[bobulak]

Well i think because it can be quite confusing Ill just bite the bullet and get either 4 Cree CBX 3070's or those Citizen CLU048-1216 that Old Salt was talking about. Mostly because I can find all the information I need from their data sheets to build the lights I want. The cheaper Chinese chips dont give me the info I need. 10 years ago when I was growing with MH/HPS lights I went with 2700k and 6500k. Does it work the same way with the cobs?

 

[Old Salt]

Well i think because it can be quite confusing Ill just bite the bullet and get either 4 Cree CBX 3070's or those Citizen CLU048-1216 that Old Salt was talking about. Mostly because I can find all the information I need from their data sheets to build the lights I want. The cheaper Chinese chips dont give me the info I need. 10 years ago when I was growing with MH/HPS lights I went with 2700k and 6500k. Does it work the same way with the cobs?

That is something that has almost as many answers as builders. Mine is 8 x 3000°K for flowering. You can see the results in my journals. I did harvest almost a lb (15-1/2oz / 440gm) from a 2' x 4' (60 x 120cm) tent. Others are building to mimic the sun as closely as possible. The Mars Hydro TS series are around 3690°K, and are used from seed to flower. If I were to build one for veg it would be in the 4500°K - 6500°K range.

I ran the numbers almost two years ago and found the cost to purchase the COB and the power (15¢/Kwh) to run it was the same over a five year period. I chose the cheaper Citizens over the CXBs.

 

[bobulak]

Ive looked at those Mars Hydro TS series lights. I dont think Ive seen to many bad reviews and most reviews are pretty positive. I also like the Spiderfarmer quantum boards as well. They both have descent par stats and can be used for both veg and flower. My friend had to get rid of 7 fem seedlings and I grabbed them. He gave me his light but tbh his seedlings look sickly and Im not sur if it was the light or something he did before he gave me the plants. I might just grab a couple of the ts 1000s and along with this philizon 1000w (250w from the wall) cree cob light im using should probably be enough.

 

[Stunned]

I used 4 X Quantum 288 Boards and have gotten more then 20 ounces off 4 plants more than once
I use 7 now

 

[bluter]

@bobulak check out led gardener dot com.

can't link to the site due to forum rules. led gardener will teach you the basics on led, the different set ups for cob, quantum, and strip lighting, and how they are wired. they have calculators for figgering out what drivers to use, and a lot of pre-loaded build suggestions with the most popular cobs and chips, as well as example builds.