Switch from store bought LED bulbs to cob?

Hi

I stealth grow in a converted chest of drawers, and I am looking to upgrade my lights, so want to ask advice from the experts.

Drawers are 28"w x 15" d x 32" h so there is not a lot of room - 2.875 sq foot floor and 7.65 cubic ft.

Currently use 9x 2700k store bought led bulbs for 129w which give 1520 lumens each with covers on and approx 10%? more with covers off. That works out at average of 106 lumens/watt with covers on - some bulbs are 15w some are 13w but all are 1520 lumen. I know lumen details are not what you guys really use, but there is no info available on efficiency, par watts etc.

When these are in the cab I lose at least 8 or 9 inches of height. I top/fim, LST and Scrog but constantly battle for space. I had a couple of leaves bleach but overall no major problems, but I seem to spend most of my time moving buds away from bulbs.

Here are pics which show near the end of my last grow and help show what I mean.



I got 3.5 oz dry which I am happy with, but I want to ask if I can make life easier for myself and be more efficient.

My diy filter is at the top back of the cab internally (you can see the brown tape around it in the first pic) and my extraction fan, duct and electrics are all on top outside, along the back 1/3rd of the cab. I have boxes and crap on top along the front 1/3rd hiding everything, so I was thinking of 3 or 4 cobs running centrally, spaced equally along the length of the cab...... but have them external. Mount them on heat sinks and cut a small circular hole in the roof to allow the heat sink to go flush and the cob to shine through. That way hopefully there will be enough of a gap to not bleach the plants and also allow enough light spread to cover the area.

I am in the Uk and not brand led. We get battered on exchange rates and delivery at the moment which is why I would prefer items uk dealers can supply please.

Individual heat sinks seem the cheapest option, delivery charges for single bars is an arm and a leg, nowhere local does them as far as I can tell. I can *cough* 'borrow' some active CPU heat sinks from old pc's at work, but have no idea about the heat rating of the sinks. I don't mind buying pin sinks or new active ones if they would be better. I have about 8" space above the cab.

I don't mind spending money, but don't want to spend a few hundred quid on something that is no more efficient that my £60 worth of store bulbs just to gain a few inches. I can grow at the moment so if it is a stupid idea it is not the end of the world.

I have read that 50w per sq foot is a rough guide. What combo would you use - 3x 50w, 4x 35, 4x 40? Less, more? Any brand more suited than another for this situation? One driver for all or one per cob?

This is where you either laugh or suggest what you would do. Thanks.

You will gain about 2x the light for the same wattage switching to cobs. It looks like you can put some pin fin sinks in there and keep the same vertical space. Another option would be to use radial extrusions. It's not a common solution but they are about 3/4 of an inch thick and do a good job dissipating up to 15 watts of heat (running 50+% efficiency, up to 30w per cob). Running them less than that is gravy. It could give you an extra couple inches in your cab... not that you need it by the look of things but it might be nice to have the extra space.

I see a 5 pack for $65. Not sure what tax/duty would be for you, and you would have to machine the mounting holes. They will fit Vero 18, Vero 29, not sure about 3590s but you wouldn't want to use them in a small cab anyway. Some of the smaller citizens would work.

http://www.ebay.com/sch/i.html?_fro...S0&_nkw=50w++aluminum+heatsink+round&_sacat=0

The ones you want are the ones with the wide spacing between fins.

Wow, fast reply Rahz.

So you think inside the cab rather than outside with holes cut through? I was worried about being too close.

Good to read about cobs being 2x the light for same wattage though. I like the sounds of that.

It's not oregano said:

So you think inside the cab rather than outside with holes cut through?

Click to expand...

Mounting them outside would be good if stealth isn't an issue. OTOH, if you've got temps under control with the current situation you should be able to match the wattage keeping them inside. A 30w cob can be as close as 3-4 inches from the canopy, closer with less wattage. Those radial sinks would sit inside about the level of the board you have the bulbs mounted on, so you would gain 3-4 inches... ends up being about the same vertical space in the end. If you mount outside you will gain a few more inches... would probably use pin sinks in that case.

Rahz said:

You will gain about 2x the light for the same wattage switching to cobs

Click to expand...

not necessarily. those are 106 lm/W with the covers on and presumably ~130 lm/W with the covers off. so maybe 50% gain at most. id double the number of bulbs, rip off all the covers, and raise it 12"

To be fair to Rahz I altered my original post after his, as it wasn't too clear on the lumen watts.

Unfortunately the bulbs in the pics are about 1" away from being as high as they go, that horizontal brown bar just above the upside down white fan is the top of the cab. With pots and about 6" of stem before the scrog screen I only have about 6" for buds before they grow into the bulbs. Hence my thought of going through the top with the cobs, as I have enough room above for heat sinks and still keep everything stealth due to the boxes I put at the front edge of the top of the cab.

you can also pull those boards out and mount them on an aluminum bar or light duty heatsink

I've not done it yet, but I think the current cheapest option in the UK is a 'hack'. I picked up one of these for £60, in mint condition.....http://www.ebay.co.uk/itm/Mars-Hydr...869368?hash=item418c4f1d78:g:o~QAAOSw9IpXxj2O

I would get the cob's off Cobkits, but for the uk this is probably the cheaper option purely due to shipping http://www.ebay.co.uk/itm/5x-CITIZE...338747?hash=item1a1d46f33b:g:f5sAAOSwV0RXvaBz

I've not opened the light up yet to see what drivers and heatsinks are in there, so I'll hang fire on buying COB's until I've checked compatibility. I'm planing something like this by @Growmau5

Thanks to everyone for their help so far

@CobKits I have a spare bulb so I took it apart and there is some pretty intricate soldering onto the board - it seems to go from behind then 2x really thin wires, as in hair thickness, go through to the front of the board and connect to the front. I have zero soldering experience so will probably kill the boards or set myself on fire just trying to take them off. As well as that the driver electronics etc, behind the board and in the actual case of the bulb, was sealed in a virtually solid bit of silicon or similar. No way was that coming out without a lot of messing about. Great idea though, thanks for the suggestion, but I think I will give that one a miss.

@DonBrennon Those cobs look ideal, I have done a load of reading over the weekend and Citizen 1212's seem to be ideal for my purpose. Thanks for the link.

As mentioned, I have read a load of threads and I 'think' I am starting to understand how it all works. I used to think you just bought say 40w cobs like you would a store bulb, and a driver and away you went. I now realise that cob wattage depends on the driver, and I knew absolutely nothing

If I have understood correctly a CLU048 1212 cob running on a 1050ma driver is roughly 37W. So if I was to run 4x cobs I would need a driver that is 150W. I am from the uk so would something like this one work? http://www.mouser.co.uk/ProductDetail/Mean-Well/ELG-150-C1050/?qs=sGAEpiMZZMt5PRBMPTWcaZHCrgNWzuwCLfarMSMGi0QVfy8Ia5JXrg%3d%3d

If I got a dimmer version I am thinking I could dim it when I have got a seedling then bump it up when it is a bit older.

I don't know about converting to Par watts etc and what you need per area, so would somebody please work out what 4x cobs running on the above driver or similar would be like in my cab - dimensions 28" x 15" at a foot away. I don't want to be under powered but then again I don't want to be like the lights on scene in Saving Grace.