Introduction: Bat Signal - Made From LED Floodlight, PVC Frame, and Whiteboard
You can make this bat signal lamp entirely from parts you can buy at Lowes, Home Depot, and Walmart. As you can see in the pics, it's very bright, even in the office during broad daylight. The shell is made from dry erase whiteboard (yes you can write on it!), the frame is made from PVC pipe, the lamp is an LED flood light, the lens is a magnifying glass, and the bat symbol was carved from a sheet of acrylic. The back panel slides up to access inside the lamp so you can adjust the focus, change the bulb, or even change the symbol.
- Dremel and grinders/sanders to carve the bat symbol
- Screw driver
- Circular saw
- (optional) PVC pipe cutter
- 4' x 8' whiteboard (also called white hardboard, dry erase board, or smooth white board)
- small black acrylic sheet (12" is more than enough)
- 1" PVC pipe ( a single 10' length should be enough)
- 1-1/4" PVC ( a single 2' length is more than enough)
- corner molding (12' total length)
- (8) PVC 1" 3 way elbow
- (4) 1/4" 20x1in thumb screw
- (8) 1/2" corner braces (also called L brackets)
- (8) 1/2" long 1/4" wide machine screws and nuts (and washers if necessary)
- (4) #16 clamp (1" to 1-1/2")
- LED flood light (NOT A CFL OR INCANDESCENT LIGHT, any heat from the light could melt the acrylic bat symbol that sits on top)
- Flood shop light fixture
Step 1: Make the Frame
First, cut the frame from 1" PVC pipe. I used a PVC cutter (1" to 1-1/2" sized) to make burr-free cuts, but you can also use a jigsaw or hacksaw.
I built the shell from whiteboard which was 3' wide, so I cut the 1" PVC pipe just short of that minus the length of the two elbow corners.
Fit the pipes into the elbows to create the frame as shown, don't glue them yet, you'll need to add the locking slide later. Actually, I've found it's held together perfectly just by squeezing them together, even after carrying it back and forth to work and different office locations, so I've never glued mine.
Step 2: Cut Bat Symbol From Acrylic Sheet
I printed out a bat symbol onto paper, then adjusted the size and reprinted until it fit on the flood light bulb (about 3-3/4"). Then I cut out the symbol and traced it onto the acrylic sheet. Using dremel tools, I carved the symbol out. It came out pretty rough, but it shows up fine on the ceiling because the edges are a little blurry anyways.
Step 3: Attach the Flood Lamp
The flood lamp fixture I bought was 7" high so I drilled holes about 7" up from the elbow fitting to raise the lamp fixture and give clearance for the electrical cord above the table. I removed the workbench clamp from the flood light fixture (it just unscrews with a wing nut) and drilled 1/4" holes in the fixture's cone. Screw in some 1/4" wide 4" long screws through the hole in the cone and into the holes you made in the PVC pipe to seat the lamp fixture. Screw in the LED flood light bulb (NOT A CFL OR INCANDESCENT LIGHT, those get way too hot for the inside of a hardboard shell).
The LED bulb still gets a little hot, so I cut a sheet of clear acrylic sits above the bulb away from it's heat. I attached the acrylic bat symbol to the clear acrylic sheet with electrical tape so it won't slip loose if the lamp gets bumped or moved.
Step 4: Create the Bat Symbol Plate
We'll need to raise the bat symbol off the bulb to improve the crispness of the image, smooth out the light, and reduce the amount of heat on the acrylic. The LED bulb doesnt produce much heat, but it still gets too warm for me to feel comfortable letting it run all weekend when I'm not around.
Cut a plate of clear acrylic to the size of the frame. Using a piece of 1" PVC, push the edge of the pipe against the corner of the plate and trace a circle for each of the corners. Cut them out with the jigsaw (the scrolling sawblade works great on acrylic).
Drill holes for the corner braces and attach with screws and nuts as in the picture.
Place it in the frame with enough clearance that you can remove the bulb when necessary.
Now place the bat symbol in the middle of the plate dead center over the bulb. I just attached it with some electrical tape so it won't dislodge while moving the lamp.
Step 5: Create the Focusing Mechanism
This is the clever part that transforms your ordinary lamp into a bat signal that shines a symbol of justice into the heavens (or ceiling tiles). If you turn on your lamp with the bat symbol on it, you'll notice that it's really just a shadowy blob because the light is diffused and unfocused. You'll need a way to not only focus the beam but you'll also need to easily adjust the focus every time you move the lamp to a surface with a new height. I was able to focus the beam with a large (7" wide) magnifying lens I found at Walmart (in the optometrist section at the front of the store) for about $15. Then with the focusing mechanism you'll build next, you can easily adjust the focus when you move the lamp to another table or demo it to your friends at work.
First, cut the handle off the magnifying lens so it fits in your frame, and trace the magnifying lens' shape on a piece of hardboard (leftover whiteboard or thin lauan plywood) that fits flush across the bottom of your frame. Drill a hole large enough to fit your jigsaw blade and using the jigsaw, cut about 1/4" inside the circle you drew, so you leave a shelf for your lens frame to rest on. Place 4 corner braces equidistant around the hole and drill holes through the plywood and affix with machine screws and nuts (and washers if necessary). Just to be safe, I wrapped electrical tape around the magnifying lens and the brackets to keep it from slipping in case you tip the lamp while carrying it or moving it.
Now cut the holes for the locking slides by resting your 1-1/4" pipe against the corner and tracing the partial circle. Cut out those circles with the jigsaw.
Cut 4" sections of 1-1/4" PVC pipe (these slide smoothly over the 1" pipe). Drill 1/4" holes in the middle of each of the sections. Using the #16 clamps, attach a corner brace (L bracket) to the top of the section with top facing up.
Slide the locking slides over each of the 1" PVC posts of the frame and screw in the thumb screws until they are snug with the inner 1" pipe.
Mark the hole location in the bottom of the cut hardboard/plywood and drill a small hole so the small screws fit. Bolt the locking slides' corner brace to the plywood using a machine screw and nut (and washer if necessary).
Now you can loosen the thumb screws and slide the whole focusing mechanism up and down with one hand to get the bat signal in focus on the ceiling. Once it's focused, tighten the thumbscrews a little so it doesn't lose focus if someone jostles or bumps the lamp.
Step 6: Create the Shell
There are a million different ways to skin a bat signal, but I chose whiteboard so I could jot notes on it with dry erase markers.
Measure the width of each side of the frame (or just one width if it's square) and mark the width on the two ends of the white board. To make a clean cut, stick painter's tape to both sides of the whiteboard at that marking point. Use a straight edge, mark the line and cut with a fine tooth saw blade (manual or circular saw). Cut a total of 4 sections to fit around the frame (but the fourth sheet should be a little narrower than the others so it can easily slide in the frame).
On 3 of the sheets, drill holes through the whiteboard into the frame and fasten with wood screws. I only needed one screw for the top and bottom corners. The fourth sheet will not be fastened and will slide freely so you can easily access the focusing mechanism and bulb later.
Cut corner molding to fit over the corners (including the empty wall) and fasten with wood glue. Use just a little because if too much is applied it will drip over the whiteboard as it dries and could ruin it. Let the glue dry over night and remove any visible drips with a razor.
Finally, slide the final wall into the groove created by the glued corner frame.
Plug in the lamp and you're done!
Participated in the
Unusual Uses Challenge
7 years ago on Introduction
What's the furthest you have projected the signal clearly?
Reply 7 years ago on Introduction
It was able to easily focus at the top of a large conference room which had a ceiling height of at least 10 feet. The height is really dependent on the size of the magnifying glass, the size of the bulb, and the length of the vertical supports in the PVC frame.
I wanted to limit the build to what you can find in local big box stores (Lowes, Home Depot, Walmart), so I had to stick with the magnifying lens and floodlight I could buy there, but I'd love to try a large fresnel lens and/or a larger bulb you can buy online and see if I could shine the bat signal in the trees or across the street. Let me know if you try it.