Automatic Plant Care Minus the Microcontroller

Plants are a nice addition to most any habitat. Many of them bear flowers or attractive foliage, some of them help filter the air, and others, like aloe vera, have medicinal properties. While some plants require very little care, they all need a little moisture at some point. Overall, plant care is a bit fiddly: water them too much and you run the risk of root rot; water too little and risk death by dehydration. Hackaday alum [Kevin Darrah] would prefer not to gamble with either condition, and so in the course of a weekend’s time, he constructed a solar-powered automatic plant watering system from components he had on hand.

While he likely had a microcontroller or two lying around, he didn’t use one. His is a system of MOSFETs that trigger a motorized pump from one of those automatic bug spray bottles to draw from a reservoir and water the plant. The solar panel charges a bank of 6800µF capacitors that [Kevin] took out of an old receiver. When the desired charge is reached, the small soil sensor module is powered, assessing the moisture level. If the level is below the threshold determined by a trimmer pot, the power from the capacitor bank is dumped to the water pump and his plant gets a drink.

[Kevin]’s design deals nicely with the possible pitfalls of solar power. He’s included a 0.1µF cap to ensure latching through the system, and added a bleed resistor so that the pump is never powered unnecessarily. After running it for a couple of days, he’s already seeing moisture regulation in the soil. His complete demonstration and theory of operation is after the break. If you’re into solar power but aren’t quite ready to ditch the µC, check out this Arduino-controlled solution for thirsty tomatoes or this PIC-powered plant pacifier.

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Handheld Linux Terminal Gets an A+

Are you all thumbs when it comes to Linux? If you follow [Chris]’s guide to building a handheld Linux terminal, that particular condition could work to your advantage. His pocket-sized machine is perfect for practicing command line-fu and honing your scripting skills on the go.

[Chris]’s creation is built around a Raspberry Pi A+ that he stripped to its essentials by removing the GPIO pins, HDMI and USB ports, the audio port, and the camera and display ports. It’s housed in a pair of plastic 2.5″ hard drive enclosures connected with a piano hinge, making it about the size of a Nintendo DS. The display is an Adafruit PiTFT touch screen and in order to save space, he soldered it directly to the Pi.

The 2.4GHz wireless thumb keyboard has all the special characters necessary for Linuxing, but the four USB ports from a dismantled hub provide flexibility. If [Chris] were to make another one, he might use this slightly larger screen from Tindie and add some charging ports to the case.

[Thanks for the tip, ar0cketman]

Etching Steel With a DC Wall Wart

[Dan Comeau] is a modern-day Renaissance DIY Jedi — or so he says… He loves re-purposing things and hacking in general. But one of his favorite pastimes is producing custom hand-made knives. He etches his logo on each, using a professional etching machine, but when a fan asked how to do it themselves, he came up with this simple and easy way to etch metal at home with a few things you probably already have!

It’s actually incredibly simple. Just by cracking open a DC power supply (a wall wart will do just fine), you can easily make your own etching/marking device with a few modifications. Ideally you want something in the range of 5-12VDC at 1A or more.  Continue reading “Etching Steel With a DC Wall Wart”

This One May Come as a Shock to Some

[Chris] seems to have commandeered a decent portion of the wife’s sewing room for his electronic adventures. As it is still her claim, she made it clear that his area needed some organization and a new desk. Dissatisfied with the look and feel of the replacement IKEA desk-like substance they acquired, he took it upon himself to ratchet up both the style and value by adding a copper laminate.

His decision is not purely based in aesthetic. If you’re following along, this means that his new electronics work surface is conductive. And yeah, it’s connected to ground at the wall. Although he doesn’t care for the stank of of anti-static mats or their susceptibility to fading and cracking, he does intend to use a tiny patch of it to keep his silicon happy.

[Chris] used a 20-gauge copper sheet that he cut and scored down to fit his Swedish sandwich wood base with enough margin for overhang. After scratching up one side of the copper sheet and one of the receiving base, he squidged down some adhesive nasty enough to require the rubber glove protocol and clamped it all together for several hours. Stay put the copper did, but stay flat it did not. After hammering down the overhang, [Chris] hand-burnished the copper in small swirls with a Scotch Brite pad to visually break up the slightly wavy surface. Instructional and hilarious play-by-play after the break.

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Micro Tesla Coil makes a Perfect Stocking Stuffer

Tesla coils are always a hit around here at the office. Giant ones that play music with modern-day chain mail wearing DJ’s, ones thrown together in garages by self-proclaimed mad scientists… But have you ever seen one that can fit in the palm of your hand?

[Ludic Science] just released this tutorial video on how to make it. It’s a miniature diagram of slayer circuitsolid state Tesla coil that’s based on the ever popular Slayer Exciter circuit that was first developed by [GBluer]. The beauty is it’s a very simple circuit to build. It consists of one power transistor, a few diodes, some resistors, and the coil. That’s it!

He even repurposes the magnet wire from a small relay, it’s literally a project you can build from scrap parts around the shop. Awesome.

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Battery Basics – Choosing a Battery for Your Project

If choosing a rechargeable battery for your project intimidates you, [Afroman] has prepared a primer video that should put you at ease. In this tutorial for battery basics he not only walks you through a choice of 5 rechargeable chemistries and their respective tradeoffs, but gives a procedure that will allow you to navigate through the specs of real-world batteries for sale – something that can be the most intimidating part of the process.

You cannot learn everything about batteries in 9 minutes, but watching this should get you from zero to the important 80% of the way there. Even if your project does not give you the specs you need to begin buying, [Afroman] tells you what to measure and how to shop for it. In particular, the information he gives is framed in the context you care about, hopefully ensuring you are not waylaid by all the details that were safe to ignore. If this is not enough, [Afroman]’s prequel video on battery terminology has more detail.

Much like your high school English teacher told you, you need to know the rules before you can choose to break them. Many of battery absolute Dos or Don’ts are written for the manufacturer, who provides for the consumer, not the hacker. Hackaday has published hundreds of battery articles over the years; search our archives when you are ready for more.

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2014 Advent Calender of Circuits

Every day this month and until Christmas, [vk2zay] is (has already been!) posting a simple but useful hack in his 2nd sort-of-annual “Advent Calender of Circuits” that many of you will want to be bookmarking. For those already saturated with the season of holiday hacks, don’t worry – other than being festively generous of him to tutor and demo a new hack every day, the hacks themselves have nothing to do with Christmas. Though he missed the last couple years we here at Hackaday covered his first month of hacks back in 2011 (now in playlist).

The daily hacks posted so far cover a wide variety of useful projects (leaning towards HV) for the electronics hobbyist who might not have all the fancy tools in their shop: DIY high voltage probes, a 1-hour tesla coil from junk, measuring RF power, a stud detector, how to test an  unknown transformer’s saturation, and many others. We cannot predict what will be posted the rest of the calender (the author hints to be making them up as he goes), but by now it is safe to say that they will not disappoint.

We would be stealing his thunder to cover them all, so, we will just pick our favorite for now:

The 1-hour tesla coil is a delightful all-shortcuts-taken hack project. If one were to listen to aficionados, teslacoiling is a highly precise hobby to get into. It appears to require careful planning, much calculation, special-ordered or soviet-surplus parts, custom jigs, fine tuning, etc. [vk2zay] shows otherwise.

Every single component of the assembly is itself a hack.

No fancy tungsten-infused grade 8 copper being water-cooled via heat pump here – the spark gap is just the bent leg of a capacitor hovering near the start of the primary winding. The power supply is a backlight inverter with a chain of Cockcroft-Walton voltage doublers. The high voltage resistor is a bunch of series-chained resistors shoved into a silicone tube. The topload is a couple cheap pie tins masking-taped together to “resemble something like a sphere.” The primary is a loose, unsupported spring of copper wire. The secondary was calculated to be whatever the height of the tube he had handy and coiled only as smoothly as a first attempt would allow. He does not even bother using wires or a switch – the circuit is completed by clipping a couple of test leads.

After all this hodgepodgery the circuit was then carefully tuned to optimize how little time it took to build (additional time used: zero). Since the frequencies do not match (1.7 vs. 2.6 mhz – 35% apart) the only thing this circuit resonates with is a hacker’s appeal for making do. Does not matter, still works. The streamers easily reach 2 inches and the author claims double that in dark lighting.

In the just 6 minute video he also manages to explain roughly what is going on theory-wise and suggest the time-effective things to considering upgrading. Almost a dozen hacks in the bag and over a dozen more to come before Christmas.

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