Thursday, May 26, 2005


Here's a short bit of video from a new monitoring system I've developed. It consists of a camera mounted in a watertight housing looking upwards through the bottom of a clear acrylic plate. I had several barnacles to settle on the plate over a year ago, and now it is possible to make out the movements of the barnacles inside their shells.

This is a screenshot of the video. Inset on the left is a view of the area where BarnieCam is mounted in the field, though you can't make out the plate in this view. The main screen has 3 barnacles in it. The simultaneous view allows you to see incoming waves and then see the barnacles feed at the same time.

The next image shows the three barnacles outlined. Also note the green arrow which points to the cirral mass of the top barnacle. This is the portion of the barnacle which you can see moving while it is feeding in the video.

Finally, there's a few seconds of video:

Monday, May 09, 2005

More McMaster stuff

For getting wires in and out of sealed housings, these liquid-tight fittings work quite well. They are black nylon, and are installed using a normal NPT pipe tap into the housing wall. They have a neoprene ring inside which clamps tightly around the jacketing of your cable to create a water tight seal. We haven't used these for subsurface projects, but they work very well for the equipment we put out in the splash zone.

Part number 69915K61
Nylon Liquid-Tight Cord Grip Fitting Straight Flex, 3/8" NPT, .16"-.31" Cord Dia
Approx $2.50 each

There are many different sizes including right-angle fittings.

Wednesday, May 04, 2005

Field equipment

The following is a list of materials we commonly use for installing experiments in the rocky intertidal. All of these can be purchased from McMaster-Carr. At the McMaster website you can enter the part numbers in bold below to take you to the corresponding catalog page, where you can find other choices on sizes and quantities, along with pricing.

My McMaster-Carr part number list:

Part number 95482A145
PVC Tri-Lobe Screw Anchor 1/4" Screw Size, 1-1/2" Length, Packs of 100
The wonderful and ubiquitous blue anchors you find left behind in the rocks everywhere. These require a hole 5/16" in diameter to install into the rock. Use the 5/16" drill bits listed below. These have no internal threads when first installed, so the first time you screw a bolt into them it will be a little stiff.

Part number 30425T18
Type 304SS Wood Thread Wire Screw Eye 7/32" Wire Dia, 1-1/8" Shank Length, 39/64" Eye ID, Packs of 10
The screw eye, installs into blue anchors, very useful along with zip-ties for securing cages, mesh, and wires.

Part number 92351A544
18-8 SS Heavy-Duty Hex Head (Lag) Wood Screw 1/4" Diameter, 1-1/4" Length, Packs of 50
These have a hex bolt head on them and require a 7/16" socket to turn. They screw into the blue anchors. Use these to bolt down settlement plates, cages, and whatever else you want. Drill a 1/4" or 17/64" hole through your object to put these through.

Part number 90286A251
18-8 SS Hex Washer Head Sheet Metal Screw Slotted, No. 10 Size, 1-1/2" Length, Packs of 100
These also get used in the blue anchors, and are sometimes useful for bolting down smaller things. They use a 5/16" hex head socket or nut driver, or else a flat bladed screwdriver.

Part number 8948A14
SDS-Shank Rotary-Hammer Drill Bit 5/16" Bit, 4" Drilling Depth, 6-5/8" O'all Length
Use this to drill holes for blue anchors using your SDS-chuck-equipped Ryobi hammer drill or electric hammer drill.

Part number 8897A4
Hammer Drill Bit 5/16" Sz, 9/32" Hex Shank, 2-1/2" D Drill, 4" L O'all
Use this to drill holes for blue anchors using your standard-drill-chuck equipped Ryobi hammer drill or electric hammer drill.

Part number 2945A29
Hand Star Drill Bit 5/16" Drill Size, 12" O'all Lg, 1-9/16" Flute Lg
Use this to drill holes for blue anchors if you don't own a gas or electric hammer drill. Bring along a hammer and prepare to suffer.

Part number 7130K19
Nylon Cable Tie 7-1/2" L, 1-7/8" Dia, Bundle 50#Tensile Strg, Off-White (0.18" wide)
Zip-ties, Cable-ties, whatever you want to call them. Secure plastic mesh to stuff, hold down cables, and do whatever else you want. 50-lb tensile strength is usually sufficient for withstanding waves if you use enough cable ties for the load.

Part number 9226T18
Type 304 Stainless Steel Woven Wire Cloth 3 X 3 Mesh, .047" Wire Diameter
Use this or a similar size for making cages and fences that will last for years. The mesh is not cheap, but gets cheaper if you buy in bulk. When mounting in the field, you can make holes through the mesh by simply drilling through it with your masonry bits and continuing into the rock below.

More stuff:
Part number 90313A107
18-8 Stainless Steel Large-Od Flat Washer 1/4" Screw Size, 9/32" Id, 1" Od, .040"-.060" Thick
Use these large fender washers with the 1/4" lag bolts to hold down cages or tuffies or whatever else needs some support.

Part number 8574K28
Polycarbonate Sheet 1/4" Thick, 12" X 12", Clear
Use Polycarbonate (aka Lexan) cut into 3"x1" strips, with a 1/4" hole drilled through the middle, to hold down cages. This can be used in place of the washers above, and obviously you can cut these to whatever size you like. The polycarbonate is much less likely to crack in half from overtightening compared to acrylic.

Part number 8560K354
Clear Cast Acrylic Sheet .25" Thick, 12" X 12"
Use Acrylic for making settlement plates in the standard 10x10cm size or whatever you like. Acrylic is cheaper than polycarbonate, so for uses like settlement plates where you need a lot of material, and ultimate strength is less of a concern, acrylic is a better choice.

Part number 5522A11
3/8" Square Drive Socket Wrench Accessory 17" Overall Length Speeder Handle, Chrome Finish
This is a useful wrench for installing the 1/4" lag bolts. If you have to put a lot of bolts in and out, this will do the job faster than a normal ratchet or hand wrench. Slap a 7/16" socket on the end. Here's another helpful hint: if you're only ever going to use this for installing bolts, have someone weld the socket onto the end of the wrench, so that you can't ever lose the socket.

You can copy and paste the contents of your McMaster cart into a word document to turn in to the purchasing office. The best method to strip out some of the HTML is to click the Print option on the McMaster order page. It will generate a new window with your order formatted for printing. Just cancel the print job and use the text in the new window to copy and paste into Word. Highlighting the order and copying it over to Word should produce a nicely formatted table.

Monday, May 02, 2005

Making an extendable remote release for the Canon 20D

I ordered a remote release off of EBay for $17.50+shipping. It's made in China by a company called Adidt. The release is called the Adidt M1 Remote Cord. It fits a variety of Canon digital SLR's which use the N3 style remote release connector, and is a cheaper (much cheaper!) substitute for Canon's own RS-80N3 remote release.

This a picture of the Canon 20D remote release connector on the body:

It has 3 pins inside. The top pin is the common pin. The lower right pin activates the autofocus when connected to the common pin. The lower left pin activates the shutter (and autofocus if not already focused) when connected to the common pin.

The quest here is to make this remote release cord longer when needed. The stock cord is 32 inches long. What follows here is a demonstration on how to splice in a pair of stereo headphone jacks in order to allow the use of common stereo headphone extension cords to make a longer release cable.

I used one male and one female 3.5mm (1/8") diameter stereo headphone jack.

These were purchased for $4 total. They are designed so that you can unscrew the housing of the connector and solder your own wires to the connector.

The first step in the process was to cut the Adidt remote release cord in half. This revealed 4 wires inside the outer jacket of insulation.

Three of the wires function in the remote release, the 4th green wire is superfluous.
The white wire acts as the common wire, and attaches to the top pin in the Canon body pictured above. The yellow wire is the Focus wire, and attaches to the lower right pin in the Canon body. The pink wire is the Shutter wire, and obviously this attaches to the lower left pin in the Canon body.

I cut the green wire out of the way, and stripped the insulation off the other three wires. The female stereo jack was up first. I attached this to the N3 plug end of the Adidt cord. After sliding the strain relief and body housing down the Adidt cord (so that they can be assembled after soldering the wires), I picked where I was going to solder each wire. The only requirement here is that you be consistent when choosing where to solder each wire onto the plugs. I chose to run the white wire to the post corresponding to the tip of the stereo plug. The yellow focus wire was soldered to the post for the middle segment of the stereo plug. The pink shutter wire was soldered to the body of the stereo plug.

The completed soldering job is pictured below. Make sure to clean up any loose strands of copper wire so that you don't accidentally make contact between two of the posts. Before sealing all this up, plug the N3 connector into the body and use a bit of paper clip or tweezers to short across the pairs of pins. Do this to ensure tht your wiring is intact. Additionally, try plugging the male stereo jack into the female jack and shorting across the pins of the male jack. This further ensures that you have continuity through the plugs. After soldering and testing, I crimped the strain relief around the outer black insulation of the Adidt cord in order to take any strain off of the solder joints themselves.

Whatever pattern of wiring you commit to on the female plug needs to be replicated on the male plug. As shown below, I once again soldered the white common wire to the tip post of the stereo plug, the yellow focus wire to the middle post, and the pink shutter wire to the main body post of the stereo plug. The strain relief was then crimped around the outer insulation of the Adidt cord.

After all the soldering and reassembly was complete, I had a functional remote release cord once again. For normal 3-ft cord length, I just plug the stereo jacks together. If I need a longer cord, I can simply insert a stereo extension cord in between my male and female jack to give me any length of cord I need.

This entire project, including the cost of the remote release unit, shipping, and the stereo plugs, cost $25. That doesn't include the cost of whatever stereo extension cord I end up getting in the future, but I have several laying around from other projects already. The splicing takes about 30 minutes if you're all set up and ready to go.

I'll also add a comment on the Adidt M1 remote release cord for those who are contemplating purchasing it. First off, it's cheap, both in price and construction. That's okay though, since it's not doing anything complicated. The switch is designed with only one button. Holding the button halfway down activates the autofocus, just like pressing the shutter button halfway down on the camera body. If you continue to push all the way down, the shutter activates. The operational feel is similar to the shutter button on the camera in terms of pressure, but it obviously doesn't feel as high quality as the camera's shutter button.

For bulb exposures, the Adidt remote release button is pressed all the way down, and then slides forward to lock into place. With the camera in bulb mode and the switch locked forward, the shutter will stay open until you come back and release the switch on the Adidt control. This feature alone justified the price of the release for me, as it makes long night exposures infinitely easier, allowing you to leave the camera and go grab another beer during the exposure.

Infrared photography for kelp surveys

I was asked about whether it was possible to still do aerial kelp surveys now that infrared film was becoming obsolete. Luckily, digital camera sensors are quite sensitive to infrared wavelengths, but they usually ship with an infrared filter over the sensor to allow for normal light photography. This can be remedied by disassembling the camera and removing the filter. This website has a great detailed series of instructions on how to do this modification on a Canon Digital Rebel (the original 6mp version, not the newer RebelXT). This is especially nice since the Digital Rebel is the cheapest digitial SLR bodies available at the time of this writing (May 2005), at around $700 for the body, $750 for the body and the base model kit lens.