Solar powered robot mows your lawn while you chill indoors


We’ve heard quite a number of radio ads lately trying to sell an automatic lawn mowing robot (like a Roomba for your grass). But wouldn’t it be a lot more fun to hack your own from an existing lawnmower? That’s what [Daniel Epperson] did. In fact, the project has been ongoing for years. But he wrote in to share the latest development which adds solar charging capabilities to the robot mower.

First off let’s discuss the fact that this is not an electric lawnmower. This is the Prius of lawnmowers, bringing together hybrid technology to cut the grass with the gasoline powered motor, and to propel the rig with electricity. [Danny's] worked hard to shoe-horn just about every feature imaginable (other than autonomy) into the thing, and that’s why the batteries can be charged from mains, an alternator powered by the gas motor, and now from the PV panel mounted on top of it. Get the entire project overview in his roundup post.

This a wireless video feed and the mower is driven by remote-controlled. So you can give your yard a trim without getting sweaty. After the jump we’ve embedded a clip of an earlier revision demonstrating that remote control. If you’re not interest in having all the features you could simply build an analog version.

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Hybrid rocket engine uses acrylic as fuel

We are fascinated by the hybrid rocket engine which [Ben Krasnow] built and tested in his shop. It is actually using a hollow cylinder of acrylic as the fuel, with gaseous oxygen as an oxidizer. We’re already quite familiar with solid rocket propellant, but this hybrid approach is much different.

When a rocket motor using solid propellant is lit it continues to burn until all of the fuel is consumed. That is not the case with this design. The acrylic is actually burning, but if the flow of oxygen is cut off it will go out and can be ignited later. This also opens up the possibility of adjusting thrust by regulating the pressure of the oxygen feed.

[Ben] milled the test rig in his shop. It’s a fat acrylic rod through which he bored a hole. There are two aluminum plates which complete either end of the chamber. The intake has a fitting for a valve which connects to the oxygen tank. There is a nozzle on the outflow end. Check out the video after the break to see a full description. You’ll also get a look at the toll the combustion heat takes on the rig.

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Fauxrarri is the PPPRS Champion

The Power Racing Series (PPPRS) is an electric vehicle competition with a $500 price ceiling. This is Fauxarri, the 2012 Champion. It was built by members of Sector67, a Madison, WI hackerspace. To our delight, they’ve posted an expose on the how the thing was built.

It should come as no surprise that the guys behind the advance electric racer aren’t doing this sort of thing for the first time. A couple of them were involved in Formula Hybrid Racing at the University of Wisconsin. That experience shows in the custom motor controller built as an Arduino shield. It includes control over acceleration rate, throttle response, and regenerative braking. But you can’t get by on a controller alone. The motors they used are some special electric garden tractor motors to which they added their own water cooling system.

If you want to get a good look at how fast and powerful this thing is head on over to the post about the KC leg of PPPRS (it’s the one towing a second vehicle and still passing the competition by).

Driving your home appliances with hybrid power

This system of hybridizing your home’s electric appliances is an interesting take on solar energy. It focuses on seamlessly switching appliances from the grid to stored solar energy as frequently as possible. There’s a promo video after the break that explains the setup, but here’s the gist of it.

Follow along on the pictograph above. We start on the left with solar panel. This feeds to a charger that tops off a 12V battery. When that battery is full, the charger feeds to the inverter which converts the 12V DC to 110V AC power. This is fed to a pass-through which is in between the appliance (in this a case a lamp) and the wall outlet. The pass-through will switch between mains power coming from the outlet, and the 110 coming from the inverter. The homeowner won’t know, or care, which power source is being used. But sunny months should result in lower energy bills. The real question is how long it takes to cover the cost of the system in saved electricity.

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Testing Lithium cells for use with a hybrid car

[Mikey] got a real deal on some A123 Pouch Cells. These are large Lithium cells that tolerate 100A discharge and 50A recharge currents, with 20 AH of life off of one charge. He’s been doing a bunch of testing to find out if the cells can go into an expandable battery pack and be made for use with hybrid cars.

We just looked in on a battery tester used for solar power car arrays. This is a similar situation except [Mikey] is focusing on the test data, rather than the apparatus. The link above is a collection of his notes from testing. Start reading at the bottom of the page up to get the chronology right. He starts to zero in on the most efficient charging methods. Immediately he’s hit with a big need for cooling as the cells take no time to pass 100 degree Fahrenheit. He continues testing with heat sink and fan, and even brings a thermal imaging camera to help with the design.

[Thanks Chris]

Hybrid roller coaster concept


Toyota recently ran an ad campaign touting “Ideas for Good” in which the actors speculated uses for Toyota Synergy Drive hybrid systems in non-automotive related applications. One idea that was floated involved using the car’s regenerative braking system at an amusement park, in an effort to reclaim and use some of a roller coaster’s kinetic energy.

Toyota sent a Prius to the team over at Deeplocal, who deconstructed it and found that the car could generate 60 amps of current when braking. That’s not an insignificant number, so they decided to create a cool demonstration showing how powerful the technology is. They built a coaster car from the Prius’ guts, and positioned it at the top of an elevated platform, which was connected to a 70 foot track. In the video embedded below they push the car from the platform and down the track, using the regenerative braking system to illuminate a large display of amusement park lights.

While the video is little more than a well-produced advertisement for Toyota, we can’t help but think that it’s pretty cool. It’s doubtful that we will suddenly see an inrush of hybrid-based roller coasters any time soon, but the concept is interesting nonetheless.

[via Notcot]

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Hacking a hack: electric hybrid Geo Metro

[Ben Nelson] turned his electric Geo Metro into a plug-in hybrid. But wait, where’d he get an electric Geo Metro? It seems that we’re one hack behind [Ben], who converted the vehicle to all electric back in 2008 using a forklift motor and some batteries. This time around he’s following the Chevrolet Volt’s example by adding a backup generator. Instead of going with a gasoline power he added a tank of propane and the generator from a Recreational Vehicle. This won’t put out enough juice to drive while the generator is running, but you can use it to extend your traveling range by pulling over for a nap while it tops off the batteries.