Wednesday, August 16, 2017

A Cheap, Arduino-based NMEA-0183 Wind Sensor/Anemometer

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This is going to be my next project the next time I destep my mast. You take the $100 Peet Bros Anemometer, which is not an NMEA product and by default works only with their own display, and plug it into an Arduino. If you have a spare Arduino, you can just build it yourself and code it by following Mechinations' guide here (you'll have to make a donation to him).

Mechinations' custom PCB board

Or you can buy his custom PCB board for the same price as an Arduino and you don't have to worry about any coding or shoddy connections. The board he made already has all the necessary connections (USB, RS-422, or Raspberry Pi) as well as a plug for the anemometer and a power input. He did all the legwork, translating the electrical signals into meaningful NMEA-0183 data.

All in all, you're looking at a capable NMEA-0183 wind instrument/sensor/anemometer for about $150, and it's in the spirit of DIY.

Expect a more detailed guide once I get around to this.

Saturday, February 18, 2017

How to Convert a Sailboat Icebox into a Refrigerator


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Pick the Location for your Norcold Compressor

The location of your compressor needs to be in a somewhat open space. The reason? It will be pumping out hot air, and if it's surrounding by this hot air, it won't be able to cool very well. That and you could risk burning a few things on your boat.

Something else worth considering is that the closer this is to your boat's centerline, the better--with your boat rolling while underway, the compressor could be subjected to significant force that, over time, could wear down its secure connections. This really isn't a big deal, so long as you secure it tightly and correctly to whatever you attached it to.

I ended up picking a location under a cockpit bench, which proved to be quite difficult to get at. But it was well ventilated (the compartment is largely empty), there's a good mounting surface (a wood bulkhead), and it's not in the cabin, so it won't pump hot air into the living space or bother me with the noise. See the video for more.

Mounting the Refrigerator Compressor

This is really dependent on its location. You'll want it to be level and flat when the boat's at rest (an upside compressor will not work very well), and you'll want it to be secure and held fast if the boat rocks a lot under way.

For my location, I built a wooden platform out of regular plywood (marine plywood is not necessary) and predrilled the mounting holes in it (the holes used to mount the compressor). Then I sanded down the outboard edge of this platform until it conformed to the curved hull shape. This wasn't perfect, but close enough.

Next, I picked up some L-shaped brackets so I could mount this wood platform securely to the wood bulkhead. Finally, to support the hanging edge (on the side opposite the bulkhead) I simply used a wooden dowel as a support leg. Since the hull is curved in this location, I also sanded this down until it fit. I also used the polyurethane foam to "stick" it to the hull, since when I did this I was unaware that two-part epoxy existed (hey, I had owned the boat for less than a month). I would strongly recommend using two-part epoxy (resin, hardener, filler, metered pumps, mixing bucket, brushes) for securing your platform to the hull or anywhere where through-bolts won't work (like a hull!).

I would recommend getting it all parts of your platform ready and installed, but wait on actually mounting the compressor until the next few steps are complete (and when you are ready to screw on the coolant tubes).

Figuring out How to Mount the Cold Plate inside an Icebox

This is going to depend on your icebox size. For me, it fit perfectly on its side, in an L-Shape, with the long part of the L extending down the center of the box. One thing to consider: It's okay if the top part of the icebox will not really be exposed to cold air. The plate will constantly cool the air, and cold air sinks, setting up a little circulation in the box. I actually preferred my box to have a "warmer" section for things that I don't want super cold, like fresh vegetables. See the video for what I mean.

My plate came with a few mounting screws, which proved to be quite difficult to use in the fiberglass interior of the icebox. So I foolishly used hotglue and only a handful of screws to mount it. Once again, I would consider using something more substantial than hot glue, but if you do use epoxy, keep in mind that you will never be able to remove the cold plate.

I would also recommend completing the next step before actually mounting and securing your cold plate.

Feeding the Cooling Coils to the Compressor

This will require some drilling. Locate the place on your icebox that will give the copper coolant tubes the most direct path to the compressor. Now you'll simply drill a 1.5 inch hole into your box in order to fit the hoses and their couples. Depending on your model, you may need more or less than a 1.5 inch hole. But once the hole is drilled, you can gently and carefully feed your coils through the hole, coupling first (when I say coupling, I'm talking about the portion you will crew into the compressor). Then feed the controller cable through too, such that the dial will be in the icebox, and the other end of the cable will plug into the compressor.

Once you've fed the coils through, you can mount your cooling plate inside the icebox so that it secure and held fast.

Screwing the Cooling Tubes to the Compressor

This is the most critical step. You've installed the cold plate in the icebox, and fed the coolant copper tubes through the hole and led them all the way to where the compressor is going to be mounted. If you have extra tube, then carefully coil it up in a big circle (see video for the example). Once you have your tubes situated, you can then fully mount and secure the compressor and its platform from the first step. Then plug in the cord that goes to the controller in the icebox, and then wire the power to the compressor to your circuit breaker (or run the 120VAC cord to the cabin where you can plug it in to a wall outlet). So now you have power to the compressor (but don't power it up yet!), it's securely mounted, and the cold plate is securely mounted in your icebox. All that's left is to attach the copper cooling hose to the compressor. 

Once you screw it in, you cannot unscrew it. This is a permanent situation, in that if you ever choose to relocate, or unscrew the tubes, you will have to buy new precharged copper cooling tubes and cold plate. The coupling/fitting will "bite" into the metal on the compressor, and form a secure connection. If it's loose, it will leak coolant and you'll have to buy new precharged copper cooling tubes and associated hot plate (get the idea?).

So to do this correctly, you put the couplings on gently, without screwing them in (just getting them ready), and the in a smooth motion, screw them on as far and as hard as you can. It won't turn very much. I don't remember how many turns it was, but I do remember it being a lot easier than I thought.

Once they're both screwed on, you will need to fill your icebox hole with fiberglass insulation and then cover both open ends with polyurethane foam. Typically ice boxes also have a little drain hole to let ice water drain out, and this is simply filled with polyurethane foam as well to keep the box insulated.

Turning on the Compressor/Refrigerator

Now that everything is installed, mounted, connected, and insulated, you can flip your circuit breaker/plug it in, and then turn the dial on the controller to set the temperature.

I've found that if I go more than half way on the temperature, things will start freezing near the bottom of the cold plate. I also have discovered that the 12v power system doesn't seem to work, but why that is, I'm not sure. It's possible that there's a fuse that popped, or that it didn't include a fuse to begin with. That's okay, though, because I'm usually not off the hook for very long.

 The Whole Package

Here's the video of my installation. I wrapped the copper coolant tubes in a foam shield to help protect them from bouncing around and abrasively rubbing into the hull. I also put a wire grill grate on top of the cold plate to make a shelf for my fridge. The video is embedded above, and here is the link: