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DIY HPS Light Reflector Hood.. Expertise Needed!

Discussion in 'Grow Room Design & Setup' started by Mr.McNooby, Jan 19, 2012.


    Mr.McNooby Member

    So i was looking for a nice HPS Light kit.. Found Lots of prefab ones for $100's of dollars... Then I found this article http://www.icmag.com/ic/showthread.php?t=54817

    It shows how to build a Reflector out of a Mailbox.. But i am wondering.. Does Chrome spray paint have good reflectivity regarding the proper light wavelengths, UV, and IR radiation reflect-ability? Or should i line the inside of the hood with Tin Foil? lol... Seriously tho... should I???

    ALSO!!!.. I want to modify the plan in this article to fit TWO lights. One 150w HPS, and one 175w MH. Both under this one reflector hood. IS THIS SAFE???
    Can I put HPS and MH bulbs that close together without explosions or other adverse side effects?..

    I also want to try to make this thing air cooled.. I have a couple extra PC case fans laying around. I have been brainstorming about this all day. It shouldn't be too hard.. I'm just getting inventor's block :P

    Anyone else have any ideas on how to modify this mailbox rig to handle 2 lights and a fan?...

    growmastercheesey Well-Known Member

    no dont put them that close just swap them one you change to 12/12
    dont use chrome or tinfoil do to the fact that it will create hotspots and actually burn your plants go to your local hydropnics store and just ask them for reflective lining they will def be able to help you out

    Mr.McNooby Member

    why would i swap them when plants need both Blue AND Red spectrum throughout the whole growth cycle?.. isn't it better to have both lights on them?

    And I can space them out.. how far apart is safe?..
    Mr Hollywood

    Mr Hollywood Member

    How's it going? Hopefully this will help with a few of your questions. I prefer making as much of my own equipment as possible, just something I enjoy doing. A few years ago when I was ready to purchase an air cooled reflector of some type I first began planning how to make my own. I ended up purchasing a prefabbed cool tube as everytime I would start designing my own, I would second guess the design, not sure if it would be up to par with a prefabbed one or not. So I said screw it and bought one. After receiving it and being able to physically hold it and mess around with it, I realized I had been over thinking and since then have made my own. Anyways, as for how close together the bulbs are I do not have a definitive answer, but I would think as long as proper ventilation were present so as to prevent overheating, it should be fine. Again, I have no proof of this so perhaps someone with more knowledge will chime in. My reasoning is simply that there is no warning on the label or website for an hps or mh bulb pertaining to the distance it must be from other HID lamps. Heat warnings sure, but not distance from additional lamps. Also look up a Son-T Agro bulb. It's an hps with a blue filament inside the same housing. I do not know if the blue portion is technically a metal halide, but it does show additional of some type can be extremely close. Again, take it with a grain of salt and research more first. :)

    As for another option that I personally would feel safe doing without question, would be to simply purchase a second mail box, and when building the reflector leave one end of each off and connect the two together making one big long reflector. Or make two separate reflectors, set them side by side, and attack the edges together, again making one big reflector only this one would be wide as opposed to long and would have separate bulb compartments.

    As for the chrome paint I wouldn't suggest it. Something very similar that I would suggest would be to swing by your local auto store and pick up a can of flat white high temp engine paint. Uber durable and flexible, and is designed to withstand temps up to 500 degrees. If you think you need something "stronger", get the brake caliper paint instead, typically good to 1000-1200 degrees. You could also go even higher and get header and exhaust paint, advertised as and considered flame proof, designed to withstand up to 2000 degrees.

    As for making it air cooled, take a trip to your local hardware store. I'll use menards as an example. Find the section with home duct work and pick up a pair of what ever size hole flanges you want. You can attach these to the ends of your reflector and can now hook up the appropriate size duct work. As for the wires you could relocate them to come out of the top, side, or travel a short length down your duct work and then exit through a hole you poke in the tubing. You could also reverse the wires and duct work if it suits your set up better and have the ducts attach to the top of the reflectors and the wires coming out the ends. Doing this will provide superior cooling capabilities as heat rises and will want to naturally enter the duct work on it's own, but will sacrifice some amount of lux as there is now a large hole on both ends which used to be reflective material. Whatever works for you.

    Also at your local hardware store with be many different size duct work. I use 6" and it was $12 for an 8 foot flexible section, getting cheaper the more you buy. Also in the same section will be multiple sizes of inline fans, typically sold as "boost-a-vent" or something similar. I have a 6" 250cfm in line fan and it cost me $25 brand new from menards. On the shelf below it was also a temperature controlled outlet made by the same company as the fan. It's designed to screw onto duct work (which is how is figures out the temp) and then has temp controls and an outlet on it. Screw it to the outside top of your reflector or vent tube, plug it in, then plug your inline fan into it. Using the thermometer in your grow area you can adjust the temp controls on the controller unit so it turn the fan on and off as needed to keep the perfect temp.

    Lastly to seal your reflectors, look in the window section of the hardware store for a piece of glass the correct shape and size. I've had luck specifically looking at basement windows and there are plenty of interesting shaped and what not.

    To attack it I suggest picking up a tube of Red RTV High temp gasket maker from the auto store when your there. Then when making the reflector, fold the bottom 1/4" of metal inwards on the two long sides. This makes a flat shelf like support for the glass on both sides. I also suggest using a couple scraps and riveting or otherwise attaching them to both short ends of the reflector and then bending them over to be used as safety tabs just in case :) Apply a small bead line of RTV the full length of both edge supports you just made and set the glass in place. Apply a small amount of RTV to your safety end tabs as well and fold up to meet the glass. Use aluminum duct tape to seat and reinforce any edges, areas, or connections that may need it.

    And there you go, sealed, air cooled, homemade reflector. Hope this helps and didn't just confuse you! :)

    Oh! I've also had fantastic luck going to Good Will and other second hand shops as well as antique shops and picking up old style candle holders and oil lamps for cheap. Many of these used an open ended glass tube for safety. This tube can then be used to make a cheap and easy cool tube reflector. The last one I made utilizing stuff I had lying around the house and garage, cost me grand total $.25 (for the candle holder) Just FYI!

    mrmadcow Well-Known Member

    if you plan to RTV your glass in place,make sure you have a way to get to the inside to clean it.

    1 more important thought. DIY is great & I prefer it over spending $$ but when it comes to electric,your homemade rig won't have a UL tag. homeowners insurance wont pay out if the fire started due to an non ul appliance & it won't matter where the fire started,your light will be blamed. & if renting, the landlord or his insurance co will sue to recover damages.
    almost 2 yrs ago, my buddy's garage burned & even though the fire started in front, (grow was back corner) he needed reciepts to prove all was UL and a statement from an electrician that all wiring was done to code befor they would pay out. this was in NY where it is illegal to grow. they couldn't arrest him because the plants were burned as well but enough of the room survived to be obvious what it was. nobody runs 4 600 watt HPS w/ hydroponics and CO2 to grow tomatoes but without the plants....

    Mr.McNooby Member

    Excellent post! Thank you very much Mr.Hollywood for taking the time to provide some quality advice. I have been thinking this whole reflector thing over and i think i'm going to just use a bit of duct tube, add a fan in the end, put the ballast in a round circuit box on the end of the unit, wire up the light and voila!.. Is glass really necessary tho?..
    Mr Hollywood

    Mr Hollywood Member

    The glass is by all means not necessary although you will have increased cooling and other benefits by having it sealed. I would suggest making it without the glass first and use it/mess around with it. During this time begin to develop and build an improved glass sealed version. By the time you're done you'll probably be ready to grow with more advanced techniques such as Co2, in which case the glass will be required. Additional benefits to a sealed reflector include being able to grow in extremely small spaces and still use massive HID lighting and being able to bring that hps in real close and just about love tap that bud. :)

    As for removing the glass to clean it when using RTV, I just use a razor blade, make a few quick slices, and the glass is free. Pull the old RTV seal off, and apply a new one after cleaning. I've used the same bottle of RTV for over a year since it doesn't really use up that much. I've also used 3m double sided tape, as well as nothing more than metal support tabs and aluminum duct tape. Although a little more costly, I would highly suggest a slightly more advanced version in which you use metal scraps to make a frame around the glass. Then use a couple small cupboard hinges and a latch or something similar to attach it to the reflector. It now opens and closes for easy cleaning, bulb replacement, etc. To make it seal pick up a roll of closed cell vinyl tape available at your local hardware store for a few bucks. One side is adhesive, the other not. Water and weatherproof. Perfect for an airtight seal. This is actually the same product I use to seal all of my hydro/aeroponic systems. It's great stuff to have around!

    Mr.McNooby Member

    OK.. I've saved your previous posts to my journal for future reference. It's a bit more than i think i can accommodate at the moment.. Here's the cabinet I'm working with:
    DSC00008.jpg DSC00001.jpg (I have gutted it since this pic.) It's about 3 feet wide x 4 feet tall x 2 and a quarter feet deep. I have a new board in the floor, and there are a few little gaps for air intake.
    And I have the back piece cut, I am just waiting to figure out a definite plan before i cut holes out of it for fans and whatnot.

    I was thinking of putting a 150 watt HID and a 175w MH bulb in there at the same time. I'll be vegging and blooming in the same box. And both blue and red are good all thru the grow. But that's not set in stone.

    IF this were your cabinet, and you HAD to work with it, what would YOU do with it?... and I'll try to follow your advice to the T.

    The materials i already have are:

    - 250w Power Supply (for a computer).
    - 4 x 250mm Computer Case Fans
    - 14 Gage wire (max 300 volts)
    - Indoor Timer (for Lights)
    - $16 Mailbox from Home Depot (for reflector hood)
    - Small chain link to suspend lights.
    - And a big old TV cabinet :P

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