A Toasty Warm Pool Without The Propane Bills

So, you’ve got the deck, you’ve got the pool and the lounger, you’ve got the summer, and you’ve got the piña colada. All set, you might say.

Sounds idilyic, but sadly we aren’t all lucky enough to live in a tropical climate. So while sipping the cocktail on the lounger you’d be warm enough the chances are that taking a dip would leave you feeling as though you’d just jumped into the Arctic Ocean. Not a problem, just turn on the pool heater. At this point you discover just how much it costs to heat a large body of water kept outdoors and open to the atmosphere. You become the kind of valued customer your liquid propane dealer sends a Christmas card to, you are reduced to living on a diet of budget ramen, and your children wear shoes with holes in them.

[ClanMan] had almost the problems outlined above, at least as far as the uncomfortable propane bills. His solution was a surprisingly simple one, he built himself a solar water heater from inexpensive PVC pipe.

It might not be immediately apparent to the uninitiated, but the key to making an efficient solar collector from such a basic material lies in careful selection of the bores of the various sections of pipe being used. The hot water feed from the propane heater had quite a narrow bore with a fast flow rate, but because [ClanMan] needed his water to linger in the collector and pick up as much solar heat as possible, he chose a much wider bore to feed it to ensure a much slower flow. The collector itself was made from multiple parallel lengths of much narrower pipe, to preserve the slow net flow across their combined cross-section while ensuring the maximum surface area contact between hot pipe and water.

The resulting heat helped take the temperature of his pool from 75 to 80 Farenheit. This may not sound like much, but was enough to make a noticeable difference.

We’ve featured quite a few solar heat projects before here at Hackaday. Best title has to go to the Hippie-Redneck Solar-Heated Kiddo Swimmin’ Pool And Hot Tub, but we’ve also featured a very tidy coiled solar collector. All this swimming is hungry work though, so how about a solar cooker made from a satellite dish?

OzQube-1: A Tiny Australian Satellite

Over the last couple of decades we have become used to the possibility of launching a satellite into orbit no longer being the exclusive preserve of superpowers. Since the first CubeSats were launched over a decade ago a myriad others have followed, and scarcely a week passes without news of another interesting project in this area.

OzQube-1 is just such a satellite, designed for imaging of the Southern Hemisphere, and it’s the brainchild of Australian [Stuart McAndrew]. He’s posted significant details of its design: it’s a PocketQube, at 50mm cubed, an eighth the volume of a CubeSat, and its main instrument is a 2 megapixel camera with a 25mm lens. Images will be transmitted to earth as slow-scan digital video via the 70cm amateur band, the dipole antenna being made from a springy tape measure which will unfurl upon launch. Attitude control is passive, coming from a magnet aligned to ensure the camera will be pointing Earthwards as it passes over the Southern Hemisphere. The project has a little way to go yet, but working prototypes have been completed and it has a Gofundme campaign under way to help raise the money for a launch.

There are plenty of Cubesat and other small satellite builds to be found on the web, here at Hackaday we’ve covered a significant number of them. Many of them are the fruits of well-funded university departments or other entities with deep pockets, but this one comes from a lone builder from Western Australia. We like that, and we wish OzQube-1 every success!

Networked Solar Birdhouses Deep in the Woods

[Oitzu] in Germany wrote in to let us know about a series of short but very informative blog posts in which he describes building a series of solar-powered, networked birdhouses with the purpose of spying on the life that goes on within them. He made just one at first, then expanded to a small network of them. They work wonderfully, and [Oitzu]’s documentation will be a big help to anyone looking to implement any of the same elements – which include a Raspberry Pi in one unit as a main gateway, multiple remote units in other birdhouses taking pictures and sending those to the Pi over an nRF24L01+ based radio network, and having the Pi manage uploading those images using access to the mobile network. All with solar power.

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Building a Sturdy Remote Control Mailbox

This DIY mailbox pretty much has it all. Not only is it waterproof and secure, it’s beautifully built and unlikely to arouse the suspicion of or induce fear in the mailman.

It’s made of 2mm thick sheet metal and features accents made of merri, a rather nice blood wood native to Western Australia. [George] of Make It Extreme built this mailbox primarily for remote control access, the idea being that each of his family members would have a key fob remote to open it. There’s an input panel under the lid in case someone loses or forgets their remote.

The setup is simple. That 12V solar panel under the address number is connected to a solar charge controller and charges a small battery. Pushing the A button on the key fob remote triggers the latch to slide over, unlocking the door. A push of the B button turns on an interior light for late-night mail collecting. The tube on the side is for leaflets and other postal miscellany. Now, the coolest feature: when mail passes through the slot, it lets [George] know by calling his cell phone. Check out the build/demo video after the break.

We’ve featured all kinds of mailboxen over the years. This wifi-enabled ‘box uses an Amazon Dash button and a Pi to play the AOL notification on the owner’s phone. The flag on this adorable mini mailbox goes up when there’s mail in the real one outside.

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Solar FPV Plane Flies Forever

We love solar power. Not only is it environmentally friendly, but it’s relatively lightweight and involves fragile high technology. Just the sort of thing that we’d want to strap onto the wings of a large model aircraft.

Solar power on a remote-controlled plane would get you unlimited cruising range. Now, a normal land-and-swap-battery process might be good enough for some people, but judging from [Prometreus]’s YouTube channel, he’s a fan of long flights over the Alps, and of pushing long-distance FPV links to the breaking point. For him and his friends, the battery power is definitely the limiting factor in how far / long he can fly.

solar-powered-plane-_-drone-_-fpv-_-built-_-rc-aircraft-rmkpjbf6dnqmkv-shot0012

All of the information we have is in the video, but that’s plenty. [Prometreus] didn’t bother with maximum-power-point tracking, but instead wired up his solar cells to work just about right for the voltage of his batteries and the level of sun that he’s seeing. So it won’t work nearly as well on cloudy days. (Check out this MPPT build that was submitted for the Hackaday Prize.)

He could switch the solar cells in an out remotely, and it’s pretty gratifying to see the consumed current in the battery go down below zero. In the end, he lands with a full battery. How cool is that?

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Raspberry Pi Wind Measurement

A well organized approach to a project is a delight to see. [Pavel Gesyuk] takes just that approach with the experiments on his blog. Experiment 13 is a multi-part series using a Raspberry Pi as the heart of a weather station. [Pavel] is looking at wind speed and direction, and temperature measurement, plus solar power for the station. One of his videos, there are many, is after the break.

electrical_02_tThe anemometer and direction sensors are stock units wired to a Raspberry Pi A+ using an analog to digital daughter board. The data from the temperature sensor is acquired using I2C. During one part of the experiment he uses an EDIMAX WiFi adapter for collecting the data.

Python is [Pavel’s’ language of choice for development and freely shares his code for others to see. The code collects the data and displays it on a monitor connected to the Pi. The experiment also attempts to use solar power to charge batteries so the station is not dependent on mains power.

The mechanical assembly shows attention to detail commensurate with his project presentation and we respect how well organized the work is.

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32C3: So You Want to Build a Satellite?

[INCO] gave this extremely informative talk on building a CubeSat. CubeSats are small satellites that piggyback on the launches of larger satellites, and although getting a 10 cm3 brick into orbit is cheap, making it functional takes an amazing attention to detail and redundant design.

[INCO] somehow talks through the entire hour-long presentation at a tremendous speed, all the while remaining intelligible. At the end of the talk, you’ve got a good appreciation for the myriad pitfalls that go along with designing a satellite, and a lot of this material is relevant, although often in a simpler form, for high altitude balloon experiments.

satellite_2-shot0002CubeSats must be powered down during launch, with no radio emissions or anything else that might interfere with the rocket that’s carrying them. The satellites are then packed into a box with a spring, and you never see or hear from them again until the hatch is opened and they’re pushed out into space.

[INCO] said that 50% of CubeSats fail on deployment, and to avoid being one of the statistics, you need to thoroughly test your deployment mechanisms. Test after shaking, being heated and cooled, subject to low battery levels, and in a vacuum. Communication with the satellite is of course crucial, and [INCO] suggests sending out a beacon shortly after launch to help you locate the satellite at all.

satellite_2-shot0003Because your satellite is floating out in space, even tiny little forces can throw it off course. Examples include radiation pressure from the sun, and anything magnetic in your satellite that will create a torque with respect to the Earth’s magnetic field. And of course, the deployment itself may leave your satellite tumbling slightly, so you’re going to need to control your satellite’s attitude.

Power is of course crucial, and in space that means solar cells. Managing solar cells, charging lithium batteries, and smoothing out the power cycles as the satellite enters the earth’s shadow or tumbles around out of control in space. Frequent charging and discharging of the battery is tough on it, so you’ll want to keep your charge/discharge cycles under 20% of the battery’s nominal capacity.

mpv-shot0001In outer space, your satellite will be bombarded by heavy ions that can short-circuit the transistors inside any IC. Sometimes, these transistors get stuck shorted, and the only way to fix the latch-up condition is to kill power for a little bit. For that reason, you’ll want to include latch-up detectors in the power supply to reset the satellite automatically when this happens. But this means that your code needs to expect occasional unscheduled resets, which in turn means that you need to think about how to save state and re-synchronize your timing, etc.

In short, there are a ridiculous amount of details that you have to attend to and think through before building your own CubeSat. We’ve just scratched the surface of [INCO]’s advice, but if we had to put the talk in a Tweet, we’d write “test everything, and have a plan B whenever possible”. This is, after all, rocket science.