MrE's Compact Hood with Integral Light Trap - OG Save
Pt1.
---
The following are somewhat detailed instructions for constructing a shielded hood/ reflector w/ an integrated light trap and electronics, designed for a small cabinet. Can certainly be scaled up for larger lights, but a 70wHPS (Casa de Pot security light mod) was used here. Was built 4 months ago and is being used for 3rd grow now.
Note: when researching other hoods/ reflectors (jackerspackle, nimby, ngb, tick etc.) the question often popped up re: bending sheet metal w/out a proper press brake. The method shown works like a dream and requires only a few pieces of scrap wood, so maybe that will be of use as well.
-> Primary Tools:
-Tin snips
-Rivet gun
-Square / Straightedge
-Utility knife
-Drill
-Good marker for layouts
-> Materials:
-Sheetmetal - picked up large sheet of decent gage sheet for $8 at casa de pot.
-HPS light
-Glass shield
-Plug and wire
-Paint - white and black - use HIGH TEMP only, I used stuff suitable for bbq grills.
-Weatherstrip
-Foil tape
Image 1
Image 2
** Light Trap Subassembly **
Will start here, as this shows the bending and all. Looking at the second image (Image 2), you'll see a) the sketch on cardboard in the background used to plan hood to fit in the small filing cab, b) the dimensioned flat pattern layout on paper, and c) a section of sheetmetal w/ the layout - try to be accurate and definitely use a square.
Image 3: The pattern is then cut w/ snips and "scored" for bending. The scoring is important to get a nice crisp bend. Use the utility knife, and make like youRe going to cut on a "fold line" and take a few passes.
The score should be on the outside of the bend.
Image 4: Folding technique - using 3 scraps of plywood. Two sheets sandwich the section that will be stationary during the bend. The third sheet is placed as shown below the section to be bent, and butting up against the bottom of the sandwich, meeting right on the bend line. Be careful not to get any of the 3rd sheet below a section not to be bent yet.
Image 5: While standing on the "sandwich", pull the 3rd sheet up with confidence. The resulting bend is shown and is very crisp, accurate and straight - guided by the score.
Don't bend completely, just as shown as the remaining degrees in the bend will be completed by hand later.
Image 6: Continue bending. Here, you'll step where the hammer is sitting.
Image 7: A narrower piece of wood is used here (scrap from the cabinet drawer).
* Paint the inside with one or more coats of flat black prior to the finish hand bends.
Image 8: Bottom view of fully folded trap.
The final bends are made by hand - simply grip the sheetmetal with the V in the fold facing your palms and squeeze. It will bend easily, and again, the score will help here.
Image 9: Top view. Note that tabs have been drilled and riveted. Would be a good time to seal the seams w/ the high temp foil tape. I didn’t do this at first (was trying for 100% metal unit) and ended up w/ tiny light leaks, so added the tape later. With the airflow through the hood it runs fairly cool anyway.
Compact Hood - Pt 2 - ** Hood Subassembly **
Pt2.
---
** Hood Subassembly **
Image 10: Scored sheet ready for folding.
Image 11: Take note of this image. It is a square section used as an insert, bent into a V shape, for reflecting light above the bulb, and is an important element of the design. Hopefully you can see the detail of the scored lines here. BTW, the fancy Kett power snips were borrowed from AF and worked well, but hand snips work just fine, and are required for getting into the little corners anyway.
Image 12: Hood and vInsert folded. The bar on the top is used to secure a 90degree bracket on the inside for holding the light fixture (note the wires sticking out). It was salvaged from the security light housing (might have been from a 150w light though).
Image 13: Rivet the vInsert in place. You can see the light bracket on the left. The rivet gun has a fancy swivel head which was more useful than expected, but any one should work ok.
Image 14: completed assembly. The final steps to get here are:
* Join the two subassemblies together. Used a small sheetmetal piece at back end (end of bulb pointing toward it), and fashioned another piece for the end closest you in the pic.
* Paint assembly with flat white high temp paint.
* Install electronics (ballast, starter, power cord to timer). NOTE - view OG FAQ for details on wiring the security light. The ballast is shown up front here and worked fine for 1st grow, but have since relocated the ballast to the back of the unit where the exit is located, thought it would add a slight bit less total heat, maybe, and no longer use carbon scrubber cartridge. Looking at (Image 1) at top of thread, you can see the exit with weatherstripping around it that mates to exhaust port in cabinet. It is in here that the ballast is now located. Secured ballast w/ sheetmetal strap, and had a bit of issue w/ ballast hum - wedging a metal shim under the ballast to make it more snug eliminated the vibration and it's practically silent now, even at startup.
* Now might be a good time to test your hood assembly!!! Yeay.
Compact Hood - Pt 3 - ** Install / Conclusions **
Pt3.
---
** Installation, observations and layout dimensions
Image 15: Hood assembly installed in cab.
* The remaining triangular shaped space on right side is used for power junction box and in front of that the timer. Keeps all electronics upstairs and away from fluids. No separate utility room need for this cab!!
There is an air space above the hood.
* Install glass shield. Tempered is best, but using regular 1/8" here as it's fairly small and little stress is placed on it. A gap of 3/4" or so is left at far end for air to enter, pass across bulb, and then flow out hood and over ballast on way out of box. You might note the two channels bent along either side of hood for glass to slide in. Glass ended up a little too large, so just taped it on - works just fine.
* Seal front of assembly. Used a material called "Reflectix". Version 1 of the cab had Reflectix on the walls and door, and when closed sealed off the front. Now using mylar, so did it as shown for current setup.
Image 16: Light on!!!
Camera was placed on floor of cab for this shot. Each image is simply a different exposure. The left image gives a good idea of where most of the light goes. It is said little light is emitted from end of bulb, and this makes that fairly clear. The right image shows the imbalance in my light distribution a bit more clearly, due to about a 3/16" misalignment of the bulb over the vInsert.
Will tweak that before next grow when glass is removed for cleaning - however, it does demonstrate how important the vInsert is and also that accuracy does matter for some parts of the setup.
Image 17: Carbon scrubber insert - abandoned this for now.
This little module was made w/ flouro light fixture grill cut to triangles and stacked and glued to achieve about 4" length. Channels are filled w/ activated carbon for scrubbing odors. It was inserted into back of cab through the opening, and then slid in.
Caused too much static pressure for the single fan being used (had to go w/ active intake), so now use stacked scrubber modules on back of cab - oh well, so much for 100% containment w/in the little cab - still stealthy.
Images 18 & 19: Dimensioned layouts If youRe still reading this, maybe building one of these is in youR future, so the actual dims for a 70w bulb would be useful. Scale/ adjust to suit other builbs.
Image 20: Buds in first grow. Just a shot to show that this light and tiny cab will produce some decent smoke. Goal is to achieve 2oz in this cab, which seems doable.
Well, there you have it, an aircooled hood assembly w/ integral light trap - all for less than $100. This took me a full day and well into the night to design and build, however, the design part was probably 80% of the work. Also doesn't count a day of searching OG to see what others had done. Could probably build one of these in an afternoon now - or maybe just a bit longer than the time is took to prepare this post!
Conclusions:
Works for me! On third grow w/ this setup and it performs well. The temp increase is about 6 to 7 degrees above ambient. More fan power should bring this down, the flow is prolly a bit low now (only 1 rotron fan on intake at this point, another tiny one below glass in corner for circulation). An active exhaust would be an improvement, as there isn't airflow through the hood when the door is removed. Didn't have fans that would fit at the time this was built. Have since picked up some smaller Rotron DC fans that will be used to add an active element to the exhaust at some point. I'd recommend this from the start.
go kindly,
-MrE
---
MarvinM92 posts
Heres some detter diagrams for anybody intrested... Marvin
---
MrE posts
MarvinM,
Thanks for the contribution - very nice! The hood had worked very well for the past 10 months. The only change from the pics is relocation of the ballast from the front of the cab to the very back where the exit is, just inside the end of the light trap. If you look at the first pic, where the square opening is surrounded by tan weather stripping (light/air seal), the ballast is now attached to the inside right there.
Also, not sure how critical the 1/2 inch bends are (mine were somewhat smaller) that are meant to hold the glass. I've simply attached the glass with standard foil HVAC tape, and it works fine (glass was slightly wider than slot, so did that).
Go Kindly,
MrE
Pt1.
---
The following are somewhat detailed instructions for constructing a shielded hood/ reflector w/ an integrated light trap and electronics, designed for a small cabinet. Can certainly be scaled up for larger lights, but a 70wHPS (Casa de Pot security light mod) was used here. Was built 4 months ago and is being used for 3rd grow now.
Note: when researching other hoods/ reflectors (jackerspackle, nimby, ngb, tick etc.) the question often popped up re: bending sheet metal w/out a proper press brake. The method shown works like a dream and requires only a few pieces of scrap wood, so maybe that will be of use as well.
-> Primary Tools:
-Tin snips
-Rivet gun
-Square / Straightedge
-Utility knife
-Drill
-Good marker for layouts
-> Materials:
-Sheetmetal - picked up large sheet of decent gage sheet for $8 at casa de pot.
-HPS light
-Glass shield
-Plug and wire
-Paint - white and black - use HIGH TEMP only, I used stuff suitable for bbq grills.
-Weatherstrip
-Foil tape
Image 1
Image 2
** Light Trap Subassembly **
Will start here, as this shows the bending and all. Looking at the second image (Image 2), you'll see a) the sketch on cardboard in the background used to plan hood to fit in the small filing cab, b) the dimensioned flat pattern layout on paper, and c) a section of sheetmetal w/ the layout - try to be accurate and definitely use a square.
Image 3: The pattern is then cut w/ snips and "scored" for bending. The scoring is important to get a nice crisp bend. Use the utility knife, and make like youRe going to cut on a "fold line" and take a few passes.
The score should be on the outside of the bend.
Image 4: Folding technique - using 3 scraps of plywood. Two sheets sandwich the section that will be stationary during the bend. The third sheet is placed as shown below the section to be bent, and butting up against the bottom of the sandwich, meeting right on the bend line. Be careful not to get any of the 3rd sheet below a section not to be bent yet.
Image 5: While standing on the "sandwich", pull the 3rd sheet up with confidence. The resulting bend is shown and is very crisp, accurate and straight - guided by the score.
Don't bend completely, just as shown as the remaining degrees in the bend will be completed by hand later.
Image 6: Continue bending. Here, you'll step where the hammer is sitting.
Image 7: A narrower piece of wood is used here (scrap from the cabinet drawer).
* Paint the inside with one or more coats of flat black prior to the finish hand bends.
Image 8: Bottom view of fully folded trap.
The final bends are made by hand - simply grip the sheetmetal with the V in the fold facing your palms and squeeze. It will bend easily, and again, the score will help here.
Image 9: Top view. Note that tabs have been drilled and riveted. Would be a good time to seal the seams w/ the high temp foil tape. I didn’t do this at first (was trying for 100% metal unit) and ended up w/ tiny light leaks, so added the tape later. With the airflow through the hood it runs fairly cool anyway.
Compact Hood - Pt 2 - ** Hood Subassembly **
Pt2.
---
** Hood Subassembly **
Image 10: Scored sheet ready for folding.
Image 11: Take note of this image. It is a square section used as an insert, bent into a V shape, for reflecting light above the bulb, and is an important element of the design. Hopefully you can see the detail of the scored lines here. BTW, the fancy Kett power snips were borrowed from AF and worked well, but hand snips work just fine, and are required for getting into the little corners anyway.
Image 12: Hood and vInsert folded. The bar on the top is used to secure a 90degree bracket on the inside for holding the light fixture (note the wires sticking out). It was salvaged from the security light housing (might have been from a 150w light though).
Image 13: Rivet the vInsert in place. You can see the light bracket on the left. The rivet gun has a fancy swivel head which was more useful than expected, but any one should work ok.
Image 14: completed assembly. The final steps to get here are:
* Join the two subassemblies together. Used a small sheetmetal piece at back end (end of bulb pointing toward it), and fashioned another piece for the end closest you in the pic.
* Paint assembly with flat white high temp paint.
* Install electronics (ballast, starter, power cord to timer). NOTE - view OG FAQ for details on wiring the security light. The ballast is shown up front here and worked fine for 1st grow, but have since relocated the ballast to the back of the unit where the exit is located, thought it would add a slight bit less total heat, maybe, and no longer use carbon scrubber cartridge. Looking at (Image 1) at top of thread, you can see the exit with weatherstripping around it that mates to exhaust port in cabinet. It is in here that the ballast is now located. Secured ballast w/ sheetmetal strap, and had a bit of issue w/ ballast hum - wedging a metal shim under the ballast to make it more snug eliminated the vibration and it's practically silent now, even at startup.
* Now might be a good time to test your hood assembly!!! Yeay.
Compact Hood - Pt 3 - ** Install / Conclusions **
Pt3.
---
** Installation, observations and layout dimensions
Image 15: Hood assembly installed in cab.
* The remaining triangular shaped space on right side is used for power junction box and in front of that the timer. Keeps all electronics upstairs and away from fluids. No separate utility room need for this cab!!
There is an air space above the hood.
* Install glass shield. Tempered is best, but using regular 1/8" here as it's fairly small and little stress is placed on it. A gap of 3/4" or so is left at far end for air to enter, pass across bulb, and then flow out hood and over ballast on way out of box. You might note the two channels bent along either side of hood for glass to slide in. Glass ended up a little too large, so just taped it on - works just fine.
* Seal front of assembly. Used a material called "Reflectix". Version 1 of the cab had Reflectix on the walls and door, and when closed sealed off the front. Now using mylar, so did it as shown for current setup.
Image 16: Light on!!!
Camera was placed on floor of cab for this shot. Each image is simply a different exposure. The left image gives a good idea of where most of the light goes. It is said little light is emitted from end of bulb, and this makes that fairly clear. The right image shows the imbalance in my light distribution a bit more clearly, due to about a 3/16" misalignment of the bulb over the vInsert.
Will tweak that before next grow when glass is removed for cleaning - however, it does demonstrate how important the vInsert is and also that accuracy does matter for some parts of the setup.
Image 17: Carbon scrubber insert - abandoned this for now.
This little module was made w/ flouro light fixture grill cut to triangles and stacked and glued to achieve about 4" length. Channels are filled w/ activated carbon for scrubbing odors. It was inserted into back of cab through the opening, and then slid in.
Caused too much static pressure for the single fan being used (had to go w/ active intake), so now use stacked scrubber modules on back of cab - oh well, so much for 100% containment w/in the little cab - still stealthy.
Images 18 & 19: Dimensioned layouts If youRe still reading this, maybe building one of these is in youR future, so the actual dims for a 70w bulb would be useful. Scale/ adjust to suit other builbs.
Image 20: Buds in first grow. Just a shot to show that this light and tiny cab will produce some decent smoke. Goal is to achieve 2oz in this cab, which seems doable.
Well, there you have it, an aircooled hood assembly w/ integral light trap - all for less than $100. This took me a full day and well into the night to design and build, however, the design part was probably 80% of the work. Also doesn't count a day of searching OG to see what others had done. Could probably build one of these in an afternoon now - or maybe just a bit longer than the time is took to prepare this post!
Conclusions:
Works for me! On third grow w/ this setup and it performs well. The temp increase is about 6 to 7 degrees above ambient. More fan power should bring this down, the flow is prolly a bit low now (only 1 rotron fan on intake at this point, another tiny one below glass in corner for circulation). An active exhaust would be an improvement, as there isn't airflow through the hood when the door is removed. Didn't have fans that would fit at the time this was built. Have since picked up some smaller Rotron DC fans that will be used to add an active element to the exhaust at some point. I'd recommend this from the start.
go kindly,
-MrE
---
MarvinM92 posts
Heres some detter diagrams for anybody intrested... Marvin
---
MrE posts
MarvinM,
Thanks for the contribution - very nice! The hood had worked very well for the past 10 months. The only change from the pics is relocation of the ballast from the front of the cab to the very back where the exit is, just inside the end of the light trap. If you look at the first pic, where the square opening is surrounded by tan weather stripping (light/air seal), the ballast is now attached to the inside right there.
Also, not sure how critical the 1/2 inch bends are (mine were somewhat smaller) that are meant to hold the glass. I've simply attached the glass with standard foil HVAC tape, and it works fine (glass was slightly wider than slot, so did that).
Go Kindly,
MrE
