Raspberry Pi Automates Your Tomato Farm

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Check out the tomato plants [Devon] grew using a monitoring system he built himself. It’s based around a Raspberry Pi. As far as grow controllers go it falls a bit short of full automation. That’s because the only thing it can actuate is the black water line seen hovering above the plants. But [Devon’s] work on monitoring and collecting sensor data should make it easy to add features in the future.

The moisture sensors pictured above monitor the soil in which the plants are growing. But he also has temperature and light sensors. These are very important when growing from seed and could be used in conjunction with a heating mat for plants that require higher soil temperatures (like pepper plants). The tomatoes are also pretty leggy. Now that he’s monitoring light levels it would be good to augment the setup with a grow light. A long term goal could even be a motorized bed which could raise the plants right up to the bulbs so they don’t reach for the light.

Don’t let the stars in our eyes distract you though. He’s done a ton of work on the project both with the physical build, and in plotting the data collected by the system. Great job!

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Giving A Crank Flashlight A Super Capacitor Overhaul

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[Caleb] was given a tiny LED flashlight which has a crank used to charge it. Unfortunately it wasn’t holding a charge, and constant cranking didn’t work very well either. He cracked it open to find a single lithium button cell. Instead of using a drop-in replacement he soldered in his own super capacitor.

The stock device is remarkably simple. It uses a standard DC motor as the generator. It’s connected to the crank using a set of gears, with the two red wires seen above connecting it to the control board. Four diodes make up a bridge rectified and apparently feed directly into the battery. No wonder that cell went kaput!

But this orientation isn’t bad for using capacitors. They can be charged directly and the switch which attaches the LEDs to voltage doesn’t interfere with their operation. The last problem was making room for them in the case. [Caleb] considered a few different approaches, but ended up just heating the plastic enclosure until it could be deformed to make room for the additional parts.

Solar Powered Hovercraft

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It looks a little bit like an octocopter, but this solar-powered hovercraft is distinctly different from its free-flying brethren. It depends mostly on ground effect for operation and to get it just a bit into the air you need a pretty large reflective rig nearby.

The vehicle needs to be even lighter than traditional quadcopters in order to function. It doesn’t carry any battery at all which presents a problem when trying to program the microcontroller board. For this it is connected to an external battery, which is removed before flight so that the control can be powered from the solar array.

What’s not shown in the image above is a mirror array used to focus more intense sunlight on the panels to bump up the available electricity. Not much is said about this, but there is one image on the project page which shows the creator standing in front of the set of four mirrors (perhaps sheets of mylar?) strung up between a couple of trees.

Alas, we couldn’t find a video of the aircraft in action. With such a delicate balsa wood frame we’re sure this thing is affected by every air current that passes its way.

[Thanks Laimonas]

Water Tank Level Meter Prevents Overflow

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Most of the homes in the area where [Raikut] lives have tanks on the roof to hold water. Each is filled from a well using a pump, with gravity serving as a way to pressurize the home’s water supply. The system isn’t automatic and requires the home owner to manually switch the pump on and off. [Raikut] made this process a lot easier by designing an LED bar indicator to monitor the water level.

The sensor is very simple. Each LED is basically its own circuit controlled by a transistor and a few resistors. A 5V signal is fed from 7805 linear regulator into the tank. The base of each transitor is connected to an insulated wire, each extending different depths in the tank. As the water rises it completes the circuit, illuminating the LED.

[Raikut] is conservation minded and built a buzzer circuit which is activated by the LED indicating the highest water level. If someone walks away from the pump switch while it’s filling the alarm will sound as it gets to the top and they can turn it off before it wastes water.

[via Reddit]

Dummy Batteries Let You Use An AC Adapter

We find it frustrating when battery operated consumer electronics don’t include a way to connect an external power supply. We try not to purchase disposable alkaline cells if we can avoid it, and this dummy battery AC adapter hack will aid in our mission.

The battery compartment shown above is for a motorized baby swing. It accepts C sized batteries (who has those just lying around?) and lacks a barrel jack to connect a wall wart adapter. [Jason Smith] mentions you can get around this by connecting your positive and ground wires directly to the conductor springs. But using a dummy battery makes it a bit easier to remove the adapter if you do want to use battery power.

Each of the orange dummy is a wooden dowel with a screw at each end. The screws are connected with a piece of jumper wire, shorting the two terminals. This completes the circuit in the battery compartment and allows him to power everything from the adapter cell at the bottom. The adapter uses an LM317 adjustable voltage linear regulator. He used fixed resistor values to dial in his target voltage. The equipment should be rather forgiving as battery voltage starts higher than the printed value and drops as the cells are used up.

This technique has been around for a long time. One of our favorites was a hack that converted an Apple Magic Trackpad to USB power.

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Electric Motorcycle Hits The Racing Circuit

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Check out that beefy electric motor hanging out where the swing arm connects to the body of this motorcycle. It’s the muscle that makes this recently completed electric motorcycle ready to race.

[Jackson Edwards] has been hard at work building this from the ground up. His goal was to make it competitive with production line motorcycles and his most recent test runs are pointing to success. The film shows off a couple of problems with the rear suspension. This actually led to him dumping the bike on a turn. He was unharmed but the control panel on the handlebars was unfortunately trashed. A bit of work fixed the handling and he was able to ride with confidence. We’re struck by how quiet the thing is as it tears past the camera at the very beginning of the video.

Sure, we’ve seen other electric motorcycles before. Those were all conversions from gas. Designing from the ground up really opened up a lot of choices not possible with a retrofit. Make sure to dig through all the posts on his blog to get the full picture.

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Update: Grow Controller Rebuilt To Last

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[The Cheap Vegetable Gardener] assembled his first grow controller about three and a half years ago. He’s been very happy with it and knows that he’ll be using it for years, maybe even decades to come. He just finished overhauling the grow controller design to help make sure he doesn’t burn down his garage one day. You have to admit, without knowing anything about the project this rendition does look safer than his original offering.

Pictured above is the weather-proof enclosure he used to house four mains-rated solid state relays. This box is isolated from the control hardware, providing heavy-duty utility plugs to interface with the heater, lights, fan, and water pump.  He mounted the Arduino board which controls the relays to the outside of the box, using the Ethernet wire to switch the SSRs. It uses a manufactured shield he designed which will help ease the pain of fixing the system if parts ever go bad.

Later on in the build he shows the grow light and heaters used in his operation. The heaters simply screw into light sockets; something we’ve never come across before.