UW camera plans
What this is: assembly instructions for a PVC pipe based case to house a small board video camera for use underwater. camcase.gif is the picture and exploded diagram to help explain the mumbling that follows.
background : This is my forth case. Case #1 and #2 was for a saticon tube based security camera using 6" pipe in the late 1980's. That camera allowed the use of a single coax cable as long as you placed a dc block before the 13" tv I used for the monitor. Case #3 and #4 were 2" pvc for a 1.5" square board camera purchased from Marlin P. Jones and Associates (www.mpja.com) when the camera cost $99.00. They're half that now. The competition is also greater and it seems as if "everyone" is selling an inexpensive video board camera now. The hobby magazine Nuts & Volts has at least 10 vendors listed.
Compare compare compare - prices vary wildly for the same model camera.
b&w cameras are cheaper than color cameras and have lower light requirements. (though that changes if you want to pay the bucks for a laboratory grade unit). I personally would stay away from the added cost of color unless I was using the unit during the day in shallow water conditions or for close inspection using lights.
I/R leds. I would ignore them. Sounds good, but the text I see mention that the I/R leds "allows camera to see up to 5ft in total dark" and that assumes in air. If you need to see in darkness which exceeds the camera, an external I/R source in excess of 6 LED's is probably required to do any good.
Some of the things I did might be overkill, but I've seen too many case designs leak during the test phase. Test the case in the water to depths much deeper than you intend and tow it at speeds in excess of that which you intend to use it. Do all of this before inserting the camera. I have yet to lunch a camera, and I've hit rock reefs with the 2" case, but luckily the zebra mussels must have saved the unit. The cheaper the video camera the less likely I'm going to cry when it finally happens. :^)
misc items required:
caulk (waterproof) used : everywhere
teflon tape - used to help seal threads on item 3 to item 5 connection
cement : I use generic multi-purpose PVC/ABS/CPVS cement. There are some concerns stated to me regarding it's use with lexan.
Determine your case length. If you intend to tow, you might want it a little longer to handle attachment of fins. I do not need fins, the unit towed nicely without it for me with a case length of 9" using 2" PVC.
Smaller pipe diameter might decrease the field of view of the camera. With a 2" pipe, make sure you place the camera lens as close to the case lens as possible to decrease the chance that the tube will be visible. In my case I have a slightly decreased view, but I like the smaller case size.
PVC cement sets RAPIDLY when used on PVC pipe. You have little time to adjust, so dry fit all pieces so you know what goes where. If you mess it up, you need to cut the piece off and start again.
adhere to proper anti-static procedures for camera, as specified by the mfg.
1) Cut your PVC pipe to length for the main body (item 8). I recommend having the pipe
much longer than required at first to allow for errors, and debug.
note: If you purchase an extra end cap (item 13) and add a few inches to the case length, you can cut the end cap off and put a new one in after you test the lens integrity. This way you can pinpoint the probable areas of leaks (lens, threads) and not have to deal with the electrical penetrations as a possibility at the same time.
2) Cut the lens (item 2) to size, to seat as tight as possible inside the male threaded splice (item 3).
3) Determine if the board camera (item 6) will fit inside the pvc tube (item 8). Some filing of the board corners might be required in small tubes. Be sure you don't file away any of the circuit traces.
4) Slide the female splice (item 5) onto the pvc pipe (item 8) so that the center seam of the splice is against the edge of the pipe (if it seems tight, once you apply glue it will slide much easier).
5) Experiment with the location of the board camera (item 6) inside the pvc tube (item 8) Mark the location that will bring the lens as close as possible to the opening. The goal is to be sure you can seat the camera atop item 7 once it is glued in place, through the opening in item 5. One thing to watch is the center lip might make this difficult if it's too close to the camera. Remember that the pvc parts will seat easier once glue is applied. What might have seemed seated when dry might go further together decreasing clearances.
6) Cut a 1" to 2" piece (item 7) of pvc pipe from the same source as item 8.
7) Cut a slice from item 7 as shown in uw_cam.gif (front view) a hacksaw works nicely. This might take a few tries, to cut the correct amount out. The goal is to reduce the diameter so that it slides easily inside the case (item 8) and contacts the interior sufficiently for gluing.
8) Glue camera mount ring (item 7) inside case body (item 8) in the location marked in step 5.
9) After the glue sets, either drill small holes in camera mount ring (item 7) to cement plastic fork tines (or ?) or drill holes to accept a couple of tiny screws. These holes should match up with the holes on the camera board. 3 pins secure my camera tightly.
10) Dry fit the female threaded splice (item 5) onto the case body (item 8). Making sure it is fully seated, test if you can install the board camera and secure it. Remove the camera from the case :^)
11) Apply glue to the inside of the smooth splice side of item 5 making sure that no glue contacts the threads, also apply glue to the outside of the case body (item 8). Attach the female threaded splice (item 5) atop the case body. It is recommended that you attach this with the threaded side facing up so that glue does not drip into the threads.
12) Dry fit lens (item 2) from the pipe splice side (smooth side) seating it against the center ridge inside the splice with male thread (item 3). Make sure it is as tight a fit as possible around the edges, and the contact surface on the inside face of the lens is smooth and even against the center lip of the splice. Remove lens.
13) If the lens is plastic : mask the center of the lens on both sides to protect from glue
and scratches. Apply a bead of glue against the center ridge, apply a bead of
glue around the edge of the lens. Keep glue away from the portion of the lens which
your camera will see through. Seat the lens against the center ridge.
You may have to provide pressure to the lens longer than normal since the plastic for
the lens probably isn't a perfect match for the glue being used.
If the lens is glass : mask the center of the lens on both sides. Apply a bead of caulk around the center ridge of the splice. Seat the lens against the caulk.
14) Apply a thin bead of caulk around the perimeter of the lens on the smooth side of the splice. This is the side facing away from the camera and will be exposed to the water.
Apply cement on the inside of the male threaded splice (smooth side) and the outside of the reducer bushing (item 1) or a piece of pvc pipe cut from the same diameter pipe as item 8. Seat item 1 inside item 3, pushing it tight against the lens.
*** if you want to play it semi-safe and intend to test the case before adding the electrical
*** penetrations continue from here ... if you want to get the thing over with, jump to *** step # 22.
15) Glue end cap (item 13) onto the case body (item 8). Let the whole thing air out. I am not confident that it's good to have the case sealed if you have a plastic lens and cement fumes inside the case.
16) Insert o-ring (item 4) against the ridge in the female threaded splice (item 5). Note: This is highly optional. If the end of the male thread doesn't contact the o-ring it isn't adding anything to the seal.
17) Wrap the male threads (item 3) with teflon tape. I used several wraps.
18) Screw the male splice/lens assembly (item 1 thru 3) into the female threads (item 5). If you use a set of plumbers wrenches, you'll be amazed at how far you can screw the thing down.
19) Apply a bead of caulk at the male:female thread juncture (item 3:5) atop the teflon tape,
sealing the seam. I also run a bead of caulk at the juncture of the end cap (item 13)
and the case body (item 8). I don't think it's required, but it makes me feel better,
and also smooths the visual lines resulting in a better looking case.
Let the caulk dry per mfg recommendations for wet locations.
20) Test Test Test. I attach light line around the case and leave a loop tied in it. I then attached a long anchor line which was weighted at the end. The theory being that if the case broke free (if it didn't flood) it would come to the surface and I'd have a chance to rescue it. I test 2-3x deeper than I expect to use it, and then motor along up to waterski speeds. When you do that, the case will rise due to friction against the line, but it's all just another piece of abuse before I think about installing a camera.
21) If it leaked ... assume the thread or the lens. Adding caulk at both locations might help. If it's dry ... it's time to pick the caulk out of the thread, unscrew the lens assembly and cut the end cap (item 13) off.
22) Drill and tap the end cap (item 13) to accept the bolts (item 9), one per electrical
connection. My camera has 3 wires (signal, power, ground) so I drilled 3 holes.
I spaced mine equally around the end cap, assuming the wires would all gather
into the center of the cap.
*** Make sure before drilling the hole that the location will allow the head of the screw or bolt to fit INSIDE the cap, and allow for the washers, ring terminal and perhaps the use of a nut driver. Outside the cap there isn't the same limitations. Drill the hole to accept the proper size tap for the bolt purchased. If you don't want to tap the cap, make sure the hole is not over size for the bolt.
23) Attach ring terminals to the wires provided with the camera. Solder all crimped connections. You might want to extend the wires and use a quick disconnect even if the camera leads are removable. If the wires are permanently attached to the camera you definitely want a quick disconnect. Remember that once this is sealed, the only access is from the lens side, so make all connections accessible from that side.
24) For each electrical connection to the camera harness (inside the case) assemble (items 9 thru 12) a bolt, star washer, ring terminal and captive washer (metal washer bonded to a rubber washer) with the rubber side towards the cap. A small dab of caulk on the rubber washer face is optional. Screw the bolt into the cap with the head on the inside of the cap.
25) For each electrical connection on the outside attach onto each bolt end (items 12 and 14) a captive washer (rubber side towards cap, dab of caulk optional) and nut.
26) Tighten each connection. Note : the bolt is left open on the outside to allow for ease of installation and replacement of external electrical connections. A nut is used to secure the captive washer and complete the assembly for test. Addition of electrical connections to the surface will not require removal of this nut.
Jump back to step 15 thru 21 to glue the end cap on and install the lens and in water TEST.
27) Assuming everything is dry you're ready to risk your camera (?) .
28) Attach external electrical connections via ring terminals (item 11) using star washer (item 10) and nut (item 14). Solder all crimps connections. Caulk or seal all exposed wires. Consider covering all crimps outside with caulk.
If you got this far, I doubt if you need me droning on :^)
!!! don't forget to remove the camera lens cap before sealing the camera in the case :^)
consider lining the inside of the pipe with black paper to decrease light reflections within the tube. Paint may (or may not) eat the pvc pipe.
Input on wire that will work. While coax cable is the best choice, for most short (100ft) lengths or there abouts (I didn't go past 100 ft) I found the least expensive answer is to use an exterior rated 3 wire electrical extension cable. The heavier insulation seems to work fine as a carrying member. If you don't want to risk it, add a tow line. Buying an 16 AWG extension cord is cheaper than buying wire. I tiewrap the cable to the threaded shackle that sits atop the tow upright (uw_cam2.gif for that drawing).
I put a small adjustable descender wing on the tow upright, it helped a little bit, but the case needs more weight to decrease the tow cable to depth ratio. I attach weight to the bottom of the case using chains. This allows the chains to rest on the bottom and the buoyant camera to remain off the bottom. And if you snag something on the bottom maybe you get to see what it was :^)
I also have some thoughts (not tested) on a tail assembly (uw_cam3.gif) that is sort of based upon my sidescan tow fish design and a pipedream.
good luck ... Ed
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