led casing made of mdf? (260Watt)

I have 5 Cree CXB3590. 4 of them run on 50Watt maximum (2700K). 1 of them run on 60Watt maximum (6500K). They are on actieve cooled pin heatsinks and never got hotter than 52C• (126F•). The temperature of the cobs is measured on the Tc point with ds18b20 sensors. the auto ignotion point of mdf is somewhere between 200-275C• (392-527F•). I can make an awesome casing for a 60x60cm (2x2feet?) growtent from mdf with a cnc lasercutter. Would it be nice to make a casing from mdf/wood, measure temps and automatically dim down if necessary or is it a stupid idea and to much risk for fire.

Gromax 3590B said:

I have 5 Cree CXB3590. 4 of them run on 50Watt maximum (2700K). 1 of them run on 60Watt maximum (6500K). They are on actieve cooled pin heatsinks and never got hotter than 52C• (126F•). The temperature of the cobs is measured on the Tc point with ds18b20 sensors. the auto ignotion point of mdf is somewhere between 200-275C• (392-527F•). I can make an awesome casing for a 60x60cm (2x2feet?) growtent from mdf with a cnc lasercutter. Would it be nice to make a casing from mdf/wood, measure temps and automatically dim down if necessary or is it a stupid idea and to much risk for fire.

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ive seen COB lights made with plastic so mdf should be ok,
are u gunna paint it

The plan is to dim down If the cobs get hotter than 85C• (185F•) for a longer lifetime of the cobs. I guess that the cobs only get that hot If a cooling fan gets defect. The sensors where on the led to calculate the lumen output in the first place. Then convert lumen to ppf for the given cob.

verticalgrow said:

ive seen COB lights made with plastic so mdf should be ok,
are u gunna paint it

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Yes because mdf swel up in moist places If not treated. I could use plywood too but it would be nice to give it a transparant finish.

What would be a good varnish with no toxic fumes for the ladys?

Gromax 3590B said:

What would be a good varnish with no toxic fumes for the ladys?

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Linseed oil

Great. Thank u.

Should be fine with that level of heat, but like you said, watch out for swelling if they get too damp/wet

Gromax 3590B said:

Yes because mdf swel up in moist places If not treated. I could use plywood too but it would be nice to give it a transparant finish.

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good point, interesting though most kitchen cabinet doors are MDF sealed with a melamine paint. Maybe thats the anti-moisture trick. no idea if it would hurt plants tho

Just paint it with a fire retardant paint and be done with it. A transparent finish on mdf is kind of pointless because it's ugly, there's no grain like real wood. It's also very soft and flexible so making an mdf frame that's too long in one direction will flex in the center depending on how you support it. I would use real wood, like birch which is pretty light and sturdy. MDF uses urea formaldehyde adhesive to bond all the particles unless you can find some that's made without, so there's that too. It's also horrible for putting screws into because it breaks apart so easily.

Gromax 3590B said:

The plan is to dim down If the cobs get hotter than 85C• (185F•) for a longer lifetime of the cobs. I guess that the cobs only get that hot If a cooling fan gets defect. The sensors where on the led to calculate the lumen output in the first place. Then convert lumen to ppf for the given cob.

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You can use this simple and easy to use bi-metal switches. They are available in normal open(NO) and normal closed(NC) for any temperature you want. The picture below is an automatic 85°C NC switch and you can wire them in series with the COB and mount it on the heatsink. If heatsink temps hits 85°C the switch opens the circuit and close it again when 70°C are reached. There are automatic and manual switches with a small reset button on the backside.

formaldehyde will off gas in your space with heat=bad choice for a humid hot grow space you think?

Who knows maybe?! I've not tried.
But there are still enough other woods that you can use ... without formaldehyde.

Randomblame said:

You can use this simple and easy to use bi-metal switches. They are available in normal open(NO) and normal closed(NC) for any temperature you want. The picture below is an automatic 85°C NC switch and you can wire them in series with the COB and mount it on the heatsink. If heatsink temps hits 85°C the switch opens the circuit and close it again when 70°C are reached. There are automatic and manual switches with a small reset button on the backside.

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Meanwell states that it is not good to power the driver without load. Dont wire the thermal switches in series with the cob. Wire them to the A-C input of the driver to switch the driver of.

I have the ds18b20 already on my cobs and I dont want to switch the lights to out If not necessary. I want to dim the lights with a microcontroller to a point that they are cool enough in case of fan failure.

Here are some pictures.

http://www.aton-growroomautomation.com/photos/IMG_0424.JPG
http://www.aton-growroomautomation.com/photos/IMG_0422.JPG
http://www.aton-growroomautomation.com/photos/IMG_0421.JPG

MDF is a horrible choice in a damp environment, but here is a trick that makes it much more suitable:

Mix 50% PVAc glue for outdoor use with 50% water and paint your MDF with that. You will see it very quickly getting sucked into the material, because MDF acts like a sponge with moisture. Keep painting with the mixture until the MDF stops sucking it in and leave it to dry for 24 hours.

You will now have made your MDF much more suitable, and the PVAc does not produce any harmful fumes. If you want to paint it, it is very compatible with acrylic paint, too. But honestly, I would advise you to use something more suitable to begin with, like plywood for instance.