Drag Your Office Aircon Into The 21st Century With Wi-Fi Control

We’ll all have worked in offices that have air-conditioning, but a little too much of it. It’s wonderful on a baking-hot day to walk into the blessèd cool of an air-conditioned office, but after an hour or two of the icy blast you’re shivering away in your summer clothing and you skin has dried out to a crisp. Meanwhile on the other side of the building [Ted] from Marketing has cranked up the whole system to its extreme because he’s got a high metabolism and an office in the full force of the midday sun.

Wouldn’t it be nice if individual air-conditioning units could be easily controlled. To that end, [Maya Posch] has made a rather nicely designed board that takes a NodeMCU board with its ESP8266 processor, and uses four of its outputs as PWM to produce 0-10 volt analogue outputs via filters and op-amps to control individual units. In addition there is an onboard CO2 sensor and a temperature sensor, with provision for an external temperature sensor. The whole fits very neatly into a standard electrical outlet enclosure.

Software wise, the system uses the Sming framework providing an MQTT  communication with a backend server that allows the users to control their aircon experience. This is very much a work in progress, so the software has yet to be put up. (Hint, [Maya], hint!) The whole project though is an extremely tidy build, in fact a thing of beauty to a standard you’d expect from a high-quality commercial product. It’s this that tipped the balance into our featuring it before the software is released, it’s one to keep an eye on, because quality like this doesn’t come every day.

This isn’t the first aircon control we’ve brought you, take a look at this one controlled through Slack.

Manufacturing Your Own Single-Origin Tea

It’s nice to take a break from hacking together the newest bleeding-edge technology, relax, and enjoy a beverage. It’s no surprise that hacks devoted to beer and coffee roasting are popular. We’ve also seen a few projects helping brew the perfect cup of tea, but none involving the actual production of tea. Today we’re going to take a short recess from modernity and explore this ancient tradition.

Consumption of tea is about equal to all other manufactured beverages, such as coffee and alcohol, combined. It is hands-down the most popular manufactured beverage in the world, and we thought it would be interesting to make some ourselves. Also the local tea is so bitter that it’s used to clean things, and it works alarmingly well. To each their own!

I started by driving into Vietnam’s Central Highlands, down what Google simply refers to as ‘unnamed road’, to about 11°52’59.3″N 108°33’49.5″E. I asked around until I found a street vendor that knew a farmer at the nearby tea plantation, and would sell us five kilograms of fresh tea. I carried it 330 kilometers back to the city, because I’m a sane person that does normal things.

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An Introduction To Solid State Relays

When we think of relays, we tend to think of those big mechanical things that make a satisfying ‘click’ when activated. As nice as they are for relay-based computers, there are times when you don’t want to deal with noise or the unreliability of moving parts. This is where solid-state relays (SSRs) are worth considering. They switch faster, silently, without bouncing or arcing, last longer, and don’t contain a big inductor.

Source Fotek SSR Specifications Sheet

An SSR consists of two or three standard components packed into a module (you can even build one yourself). The first component is an optocoupler which isolates your control circuit from the mains power that you are controlling. Second, a triac, silicon controlled rectifier, or MOSFET that switches the mains power using the output from the optocoupler. Finally, there is usually (but not always) a ‘zero-crossing detection circuit’. This causes the relay to wait until the current it is controlling reaches zero before shutting off. Most SSRs will similarly wait until the mains voltage crosses zero volts before switching on.

If a mechanical relay turns on or off near the peak voltage when supplying AC, there is a sudden drop or rise in current. If you have an inductive load such as an electric motor, this can cause a large transient voltage spike when you turn off the relay, as the magnetic field surrounding the inductive load collapses. Switching a relay during a peak in the mains voltage also causes an electric arc between the relay terminals, wearing them down and contributing to the mechanical failure of the relay.

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A Thoughtful Variety Of Projects And Failures

Our friends at [The Thought Emporium] have been bringing us delightful projects but not all of them warrant a full-fledged video. What does anyone with a bevy of small but worthy projects do? They put them all together like so many mismatched LEGO blocks. Grab Bag #1 is the start of a semi-monthly video series which presents the smaller projects happening behind the scenes of [The Thought Emporium]’s usual video presentations.

Solar eclipse? There are two because the first was only enough to whet [The Thought Emporium]’s appetite. Ionic lifters? Learn about the favorite transformer around the shop and see what happens when high voltage wires get too close. TEA lasers? Use that transformer to make a legitimate laser with stuff around your house. Bismuth casting? Pet supply stores may have what you need to step up your casting game and it’s a total hack. Failures? We got them too.

We first covered ionocraft (lifters) awhile back. TEA lasers have been covered before. Casting is no stranger to hackaday but [The Thought Emporium] went outside the mold with their technique.

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The Illuminated Waterways Of The United States

A recent convert to the ways of the laser cutter, redditor [i-made-a-thing] was in want of a project and — stumbling on some waterways maps on Etsy — launched into fabricating an illuminated map of all the waterways in the United States.

The map itself was laser-cut out of 1/4 inch plywood at his local makerspace. Thing is, smaller rivers and tributaries were too narrow at the scale [i-made-a-thing] wanted, so he ended up spending several hours in Photoshop preparing the image so larger rivers would be laser-cut — and not break off– while the rest would be etched onto the surface. After testing the process by making a few coasters, he was ready to get started on the real deal.

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Battery Management Module Hacked For Lithium-Iron Battery Bank

In a departure from his usual repair and tear down fare, [Kerry Wong] has set out on a long-term project — building a whole-house battery bank. From the first look at the project, this will be one to watch.

To be fair, [Kerry] gave us a tease at this project a few months back with his DIY spot welder for battery tabs. Since then, he appears to have made a few crucial design decisions, not least of which is battery chemistry. Most battery banks designed for an inverter with enough power to run household appliances rely on lead-acid batteries, although lithium-ion has certainly made some inroads. [Kerry] is looking to run a fairly small 1000-watt inverter, and his analysis led him to lithium-iron cells. The video below shows what happens when an eBay pack of 80 32650 LiFePo4 cells meets his spot welder. But then the problem becomes one of sourcing a battery management system that’s up to the charge and discharge specs of his 4s battery pack. We won’t spoil the surprise for you, but suffice it to say that [Kerry] really lucked out that only minimal modifications were needed for his $9 off-the-shelf BMS module.

We’re looking forward to seeing where this build goes, not least because we’d like to build something similar too. For a more traditional AGM-based battery bank, check out this nicely-engineered solar-charged system.

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A Massive Adjustable Standing Desk From Scratch

Standing at your desk all day is healthier by far than sitting, but the commercial options tend to be expensive. [drivenbyentropy] had to contend with a heater right where the desk would go, but building an adjustable office desk to accommodate it turned out — well — gorgeous.

Two 18″ heavy duty 12 V DC actuators raise and lower the desk with a 600 lbs static load capacity and 200 lbs of  lifting load each. One actuator is actually slightly faster than the other, so instead of working out something fancy, [drivenbyentropy] simply extended the cable length on the faster actuator to disguise the difference.

Framed with some standard 2×4’s and sheathed with plywood, the massive four by eight foot desk has twelve ball-bearing drawer slides in the legs to add stability and smooth out height adjustments. Because of its size and having to build around the heating unit, the desk is stuck in the room since it does not easily come apart. There is, however, easy access to the two electronics compartments for troubleshooting!

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