Britain is famously known as a land of manners and hospitality. Few situations could make an Englishman’s stiff upper lip quiver, short of running out of tea bags while entertaining house guests. Thankfully, [The Gentleman Maker] is here and living up to his name – with a helpful tea monitor to ensure you’re never caught out again.

The Intelli-T, as it has been dubbed, monitors tea inventory by weight. An Arduino Uno combined with a HX711 IC monitors a load cell mounted under a canister, with a reed switch on the lid. Upon the canister being open and closed, the Arduino takes a measurement, determining whether tea stocks have dipped below critical levels. If the situation is dire, a Raspberry Pi connected over the serial port will sound an urgent warning to the occupants of the home. If there is adequate tea, the Raspberry Pi will instead provide a helpful tea fact to further educate the users about the hallowed beverage.

It’s a fun project, and one that has scope for further features, given the power of the Raspberry Pi. A little more work could arrange automatic ordering of more tea online, or send alerts through a service like IFTTT. We’ve seen [The Gentleman Maker]’s uniquely British hacks before, such as the umbrella that tells you the weather. Video after the break.

[Nubmian] wrote in to share his experiments with measuring airflow in an HVAC system. His first video deals with using with ultrasonic sensors. He found an interesting white paper that described measuring airflow with a single-path acoustic transit time flow meter. The question was, could he get the same effects with off-the-shelf components?

[Nubmian] created a rig using a pair of typical ultrasonic distance sensors. He detached the two transducers from the front of the PCB. The transducers were then extended on wires, with the “send” capsules together pointing at the “receive” capsules. [Nubmian] set the transducers up in a PVC pipe and blew air into it with a fan.

In his second video, [Nubmian] sets up a test rig consisting of a multimeter connected to an airflow sensor. The multimeter is soon replaced by an Arduino with the help of an AD623ARZ amp. The wires for that setup needed some shielding. Aluminum foil connected to the ground did the trick.

For more HVAC projects check out this pinwheel flow meter and [Adam]’s piece on HVAC techs, hackers who make house calls.

Is it too much to ask for a home to have a little ‘smart’ built-in? If you’ve ever woken up (or come home) to your dwelling being flooded, you’ll know how terrible it feels, how long it can take to recover from, and how stressful it can be. Yeah, it’s happened to us before, so we really feel for [David Schneider]. He woke up one Sunday morning to a whole lot of water in his house. The inlet valve for his washing machine somehow got stuck in the open position after putting a load of laundry in the previous night.

[David] took progressively complex measures to prevent a broken water feed flood from happening in the future. First, he lined the entire floor of his laundry closet with a steel tray. OK, that’s a good start but won’t prevent another disaster unless it is caught very quickly. How about a simple audible water alarm? That’s good and all if you’re home, but what if you’re not?

Next, he installed a valve with a mechanical timer on the water line for the washing machine which closes automatically after 2 hours of being opened. Much better, but what about all the other thirsty appliances around the house? After searching online a little, he found plenty of whole house systems that would work for him, but there were 2 problems with these. First, most were network-based and he didn’t want to IoT-ify his house’s water system. Second, they were overpriced.

Of course the solution was to put together his own system! First, he purchased a few mostly inexpensive things — a wireless alarm, some water sensors, and a motorized ball valve. Then he collected the last few things he needed from what he had on hand around the house, and got to work connecting the 4 LEDs on the alarm to 4 analog input pins on his Arduino. Next, he added a relay between the Arduino and the motorized ball valve.

If a sensor detects water, it tells the alarm about it (wirelessly), which triggers the Arduino to energize a relay that is connected to the motorized ball valve, causing it to shut off the main water line for the entire house. Disaster averted! Sure, it’s a fairly simple hack, but it works, meets his requirements, and now he sleeps better at night knowing he won’t wake up (or come home) to an indoor swimming pool.

It’s surprising that we haven’t seen more hacks like this given it’s such a common problem. The closest thing we can remember is an overflow sensor for an aquarium. If homes came standard with a water main shutoff system, it would remove a stressful event from our lives and maybe even lower our insurance premium.

What do you do if your light switch is too far from your desk, and you’re in a rental property so you can’t put in extra wiring to install an electronic control for it? Get up and turn it on or off by hand? Of course not!

If you are [Guyfromhe], you solve this problem with a servo attached to a screw-on light switch faceplate, and you control it with a pair of Arduino/nRF24L01 combos. It’s a pretty simple arrangement, the wireless link simply takes the place of a serial cable that instructs the Arduino on the light switch to operate the servo that in turn moves the switch. The whole thing is triggered through his home automation system, which in turn responds to an Amazon Dash button on his desk. Yes, it’s complex. But turning on the light has been automated without intrusion into his landlord’s domain, and that’s all that matters.

On a more serious note, he’s put some Arduino code up on his write-up, as well as a YouTube video we’ve put below the break.

This is by no means the first such switch we’ve seen, after all we featured a nicer 3D printed servo light switch the other month, and one with a breadboarded Arduino in 2015. While we’re at it though, it would be nice to see a few designed for European switches too.

If you buy a used heat pump that was made in China and try to use it in Northern Europe, there are bound to be issues. If your heat pump ends up encased in a block of ice that renders it ineffective, you’ve got two choices: give up and pump a proper heater, or hack a new ice-busting brain board into the heat pump and get back to life.

[Evalds] chose the latter course, obviously, and in the process he gives us a pretty good look at how heat pumps work and how to overcome their deficiencies. In [Evalds]’ Latvia, winters can be both cold and humid, which can worsen an inherent problem with air-coupled heat pumps: they tend to ice up. As the outside coil is cooled to pick up as much heat as possible from the outside air, water vapor condenses out on the coils and freezes. Most heat pumps account for this by occasionally running in reverse, heating the outdoor coils to clear the ice buildup. [Evalds]’  had nothing more than a simple timer to kick off the defrost cycle, and it wasn’t keeping up with the Latvian winter. An Arduino replaced the OEM controller, and wired up to temperature sensors and an IR sensor that watches for ice buildup on the lower part of the coil, the heat pump is now much better behaved.

Of course it wasn’t as smooth as all that — [Evalds] has some hoops to jump through, including EMI problems and a dodgy Arduino clone. But he stuck with it and brought the heat pump back online, likely at far less expense than HVAC techs would charge for a service call.

If like us you live in mortal fear of someone breaking into your house when you’re on vacation and starting a dryer fire while doing laundry, this full-featured IoT laundry room monitor is for you. And there’s a school bus. But don’t ask about the school bus.

In what [seasider1960] describes as “a classic case of scope creep,” there’s very little about laundry room goings on that escapes the notice of this nicely executed project. It started as a water sensor to prevent a repeat of a leak that resulted in some downstairs damage. But once you get going, why not go too far? [seasider1960] added current sensing to know when the washer and dryer are operating, as well as to tote up power usage. A temperature sensor watches the dryer vent and warns against the potential for the aforementioned tragedy by sounding an obnoxious local alarm — that’s where the school bus comes in. The whole system is also linked into Blynk for IoT monitoring, with an equally obnoxious alarm you can hear in the video below. Oh, and there are buttons for testing each alarm and for making an Internet note to reorder laundry supplies.

We’ve seen a spate of laundry monitoring projects lately, all of which have their relative merits. But you’ve got to like the fit and finish of [seasider1960]’s build. The stainless face plate and in-wall mount makes for a sleek, professional appearance which is fitting with the scope-creepy nature of the build.

IKEA’s products are known for their clean, Scandinavian design and low cost, but it is their DIY or “assemble it yourself” feature that probably makes them so popular with hackers. We seem to receive tips about IKEA hacks with a consistent regularity. [Robin Reiter] has a Bekant Sit/Stand motorized table with buttons to raise and lower the surface, but it doesn’t have any memory presets. That’s a shame because it requires a lot of fiddling with the up/down buttons to get it right every time. It would be nice to press a button, go grab a Coffee, and come back to find it adjusted at the desired height. With a little bit of hacking, he was able to not only add memory preset buttons, but also a USB interface for future computer control.

The existing hardware consists of a PIC16LF1938 micro-controller with two buttons for movement control and a LIN bus  protocol which communicates with the automotive grade motors with integrated encoders that report position values. After a bit of sniffing around with his oscilloscope and analyzer, he was able to figure out the control codes for the motor movements. For some strange reason, however, the LIN signals were inverted, so he had to introduce a transistor signal inverter between the PIC master and the Arduino Nano that would act as a slave LIN node. Software was made much easier thanks to an Arduino library developed by [Zapta] for the LIN Bus signal Injector, The controls now have four buttons — two to replicate the original up/down movements, and the other two to act as memory presets.

The code, schematic and a simple wiring layout are posted on Github, in case there are others out there who’d like to replicate this hack. Check out the video after the break where he gives a walk through the code.

[Tim] had a problem with his microwave. The buzzer was exceptionally annoying, and once his hot pockets or pizza rolls were done, the buzzer wouldn’t shut off. A two-kilohertz tone infected his soul. It was the only sound echoing in a Boschian nightmare of reheated frozen food.

Unlike an existential ennui, an annoying buzzer in a microwave is something anyone can fix. [Tim] just took a pair of pliers to the buzzer and ripped it off the PCB. This left him with another problem — how to tell when his food was done. This was solved by putting the Windows XP startup sound in his microwave.

With the buzzer out of the way, [Tim] took an Arduino nano and loaded it up with the Windows XP startup sound. There isn’t much Flash on the Arduino, but it could hold an 18kB sample, enough to play the startup sound at 8kHz. The sound itself is PCM audio and easily stuffed into a sketch.

The Arduino listens for the 2kHz tone generated by the microwave and sends the XP startup sound through a tiny class D amplifier. After mounting a speaker inside the microwave, [Tim] has a ｖｅｒｙ　ｖａｐｏｒｗａｖｅmicrowave.

[via Hackaday.io]

Who didn’t dream of a hidden door or secret passage in the house when they were kids? Some of us still do! [SPECTREcat] had already built a secret door in a fully functioning bookcase with a unique opening mechanism. The intriguing mechanism allows the doors to start by sliding slightly away form one another before hinging into the hidden space. Their operation was, however, was manual. The next step was to automate the secret door opening mechanism with electronics.

The project brain is an off-the-shelf Arduino Uno paired with a MultiMoto Arduino shield to drive 4 Progressive Automations PA-14 linear actuators. These linear actuators have 50lb force, allowing the doors to fully open or close within 10 seconds and maintain a speed that wouldn’t throw the books off the bookcases.

Not wanting to drill a hole through the bookshelf for a switch or other opening mechanisms, [SPECTREcat] added a reed switch that is activated on the other side by a DVD cover with a magnet inside. In addition to that, there is a PIR sensor on the inside room to automatically close the doors if no motion is detected for 2 hours. Dont worry, there’s also a manual switch inside just in case.

Using one of the items on the shelf to trigger the secret passage is a classic move. He could also have used a secret knock code, like the Secret Attic Library Door we covered in the past. Check out the video below to see the hinge and slide movement in action.

We’ll admit it: we sometimes overcomplicate things. Look at [Peter Weissbrod’s] automated cat feeder, for example. It isn’t anything more than a bottle, a servo, some odds and ends, and an Arduino. However, it lets him sleep in without his cat waking him for service.

We looked at the code and thought, “This thing will just dispense food all the time! That’s not what you want!” Then we looked closer. [Peter] uses a common household timer to just turn the device on in the morning, let it run for a bit, and then turns it off. You can see a video of the mechanism, below.

Honestly, we have mixed feelings. As we are sure someone’s already quit reading to comment: you don’t really need an Arduino for this. If it were doing the timing, that might make it more justifiable. Or perhaps have it sense daylight to feed in the morning. Still, Arduinos are cheap (we just picked up some tiny Pro’s for about $3) and it is a more flexible arrangement than, say, a 555 driving the servo.

We have seen many cat feeders over the years. Some of them use custom components. Others use whatever you have on hand (including another kitchen timer). However you do it, one thing is clear: When the aliens come and observe life on Earth, they will doubtless conclude that the cats are in charge.