Remote MQTT Temperature Sensor Shows How It’s Done

First of all, there are definitely simpler ways to monitor remote temperatures, but [Mike]’s remote MQTT temperature sensor and display project is useful in a few ways. Not only does it lay out how to roll such a system from scratch, but it also showcases system features like solar power.

After all, if one simply wants to monitor temperature that’s easily done, but once one wishes to log those temperatures and use them to trigger other things, then rolling one’s own solution starts to get more attractive. That’s where using someone else’s project as a design reference can come in handy.

[Mike’s] solution uses two Wemos D1 boards: one with a DS18B20 temperature sensor for outdoors, and one with a small OLED screen for an interior display. The external sensor relies on a rechargeable 18650 cell and a solar panel for a hassle-free power supply, and the internal sensor (of which there can be many) has a cute enclosure and is powered by USB. On the back end, a Raspberry Pi running an MQTT gateway and Node Red takes care of the operational side of things. The whole system has been happily running for over two years.

What is MQTT? It is essentially a messaging protocol, and takes care of the whole business of reliably communicating data back and forth between IoT devices. It scales very well and doesn’t need to be hard or intimidating; our own [Elliot Williams] can tell you all about implementing it.

NTP server heated with Bitcoin mining dongles

Bitcoin Mining ASICs Repurposed To Keep NTP Server On Track

They say time is money, but if that’s true, money must also be time. It’s all figurative, of course, but in the case of this NTP server heater powered by Bitcoin mining dongles, money actually does become time.

This is an example of the lengths to which Network Time Protocol aficionados will go in search of slightly better performance from their NTP servers. [Folkert van Heusden], having heard that thermal stability keeps NTP servers happy, used a picnic cooler as an environmental chamber for his  Pi- and GPS-based NTP rig. Heat is added to the chamber thanks to seven Block Erupter ASIC miner dongles, which are turned on by a Python script when a microcontroller sends an MQTT message that the temperature has dropped below the setpoint.

Each dongle produces about 2.5 Watts of heat when it’s working, making them pretty effective heaters. Alas, heat is all they produce at the moment — [Folkert] just has them working on the same hash over and over. He does say that he has plans to let the miners do useful work at some point, not so much for profit but to at least help out the network a bit.

This seems like a bit of a long way around to solve this problem, but since the mining dongles are basically obsolete now — we talked about them way back in 2013 — it has a nice hacky feeling to it that we appreciate.

Picture of the automatic blind controller and three servo motors, all in their enclosures, displayed on a table.

Automated Window Blinds Using MQTT And Home Assistant

Finnish software engineer [Toni] is on a quest to modernize his 1991 house, and his latest project was to automate the window blinds and control them using Home Assistant. Unless your blinds have built-in motors, most of the effort of such a project centers around how to integrate and attach the motor — and as [Toni] points out, there are tons of different blinds with all kinds of operating mechanisms. But once you solve that issue, half the battle is over.

These particular blinds require less than one turn of the control rod to go from fully open to fully closed, and [Toni] selects a 270-degree range-of-motion, 20 kg*cm torque servo motor to drive them. He really wanted to install the motor inside the window, but it just wouldn’t fit. Instead, each servo motor is mounted in a custom 3D-printed case installed on the window frame just below the operating rod. An ESP8266-based controller box is installed above the window, hidden behind curtains, and operates all three servos.

On the software side of things, the project is coded in C++ and uploaded using the Ardiono IDE. The blinds communicate to [Toni]’s Home Assistant network using MQTT. All the software is available on the project’s GitHub repository, and the 3D-printed case design is posted on Thingiverse. Even though your blinds may be of a completely different design, we think many parts of [Toni]’s project are still useful — do check out this project if you’re thinking about doing something similar. The notion of motorized window blinds has been around for a some time — we covered one project way back in 2013 and another in 2016. If you have added automation to your window blinds, let us know how it went down in the comments section.

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Voice-Controlled Smart Home From The Foundation Up

Smart homes are becoming an increasingly popular way to automate one’s home, whether it’s turning on lights, closing blinds, or even feeding pets. But the commercial offerings often rely on an internet connection to reach servers in order to work, which invites a lot of privacy concerns for a large percentage of us as well as being inconvenient when the internet is down. Essentially the only way to have a privacy-respecting, self-sufficient smart home is to build one on your own from the ground up, which is exactly what [Xasin] has done with this project.

This build is based on ESP32 modules with a Raspberry Pi as a hub, but it’s not as simple as a MQTT implementation. Not only does the self-contained home automation setup not rely on any outside services, but a failure of the central Pi server will not impact the nodes either as they are configured to continue operating independently even without central control. This allows for a robust home automation implementation without a single point of failure, and also includes some other features that are helpful as well including voice control, all while retaining a core design philosophy that makes it relatively easy to build.

Not only is the build technologically impressive for its standalone capabilities and its elimination of privacy concerns, but [Xasin] also did an excellent job with the physical design as well, adding plenty of RGB and a hexagonal enclosure that gives it a unique look wherever its is placed. If you’re renting right now or otherwise unable to interface any automation with your current home, be sure to take a look at some projects that do home automation without making any permanent changes.

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Adding MQTT To A Solar Powered PIR Light

The size and price of the ESP wifi modules have quickly made them into one of the preferred building blocks for IoT devices. Unfortunately they are not particularly well suited for very low power applications.  [LittlePetieWheat] wanted to add MQTT to a cheap PIR solar light, so he paired an ESP with an Attiny85 to hold it to a strict power budget.

Most of these lights contain some sort of no-name microcontroller that monitors the analog PIR sensor, and turns on the LEDs as required. [LittlePetieWheat] replaced the PIR sensor with one that gives a digital output for simpler interfacing. The Attiny serves as the low power brains of the project. Its tasks include reading the solar panel and battery voltages, and PIR output. When movement is detected by the sensor, it activates a clever little latching power circuit to power on the ESP01 just long enough to send a MQTT message. The LEDs are only turned on if there is no power coming from the solar panel. The solar power is stored in a 18650 battery.

The Attiny85 might not be a powerhouse, but it is perfect for simple, low power applications like this. We’ve also seen it pushed to its limits by running tiny machine learning models, or receiving software updates over I2C. Continue reading “Adding MQTT To A Solar Powered PIR Light”

Hamster Goes On Virtual Journey

Hamsters are great pets, especially for those with limited space or other resources. They are fun playful animals that are fairly easy to keep, and are entertaining to boot. [Kim]’s hamster, [Mr. Fluffbutt], certainly fits this mold as well but [Kim] wanted something a little beyond the confines of the habitat and exercise wheel and decided to send him on a virtual journey every time he goes for a run.

The virtual hamster journey is built on an ESP32 microcontroller which monitors the revolutions of the hamster wheel via a hall effect sensor and magnet. It then extrapolates the distance the hamster has run and sends the data to a Raspberry Pi which hosts a MQTT and Node.js server. From there, it maps out an equivalent route according to a predefined GPX route and updates that information live. The hamster follows the route, in effect, every time it runs on the wheel. [Mr Fluffbutt] has made it from the Netherlands to southeastern Germany so far, well on his way to his ancestral home of Syria.

This project is a great way to add a sort of augmented reality to a pet hamster, in a similar way that we’ve seen self-driving fish tanks. Adding a Google Streetview monitor to the hamster habitat would be an interesting addition as well, but for now we’re satisfied seeing the incredible journey that [Mr Fluffbutt] has been on so far.

Give Your Smart Home A Green Thumb With MQTT

We have all been stuck inside for too long, and maybe that’s why we have recently seen a number of projects attempting to help humans take better care of their housemates from Kingdom Plantae. To survive, plants need nutrients, light, and water. That last one seems tricky to get right; not too dry and not drowning them either, so [rbaron’s] green solder-masked w-parasite wireless soil monitor turns this responsibility over to your existing home automation system.

w-parasite MQTT diagram

Like this low-power soil sensor project and the custom controller for six soil sensors, [rbaron’s] w-parasite uses a “parasitic capacitive” moisture sensor to determine if it’s time to water plants. This means that unlike resistive soil moisture sensors, here the copper traces are protected from corrosion by the solder mask. For those wondering how they work, [rbaron]’s Twitter thread has a great explanation.

The “w” in the name is for WiFi as the built-in ESP-32 module then takes the moisture reading and sends an update wirelessly via MQTT. Depending on the IQ of your smart-home setup, you could log the data, route an alert to a cellphone, light up a smart-bulb, or even switch on an irrigation system.

w-parasite circuit board in a potted plant[rbaron] has shared a string of wireless hacks, controlling the A/C over Slack and a BLE Fitness Tracker that inspired more soldering than jogging. We like how streamlined this solution is, with the sensor, ESP-32 module, and battery all in a compact single board design. Are you asking yourself, “but how is a power-hungry ESP-32 going to last longer than it takes for my geraniums to dry out?” [rbaron] is using deep sleep that only consumes 15uA between very quick 500ms check-ins. The rechargeable LIR2450 Li-Ion coin cell shown here can transmit a reading every half hour for 90 days. If you need something that lasts longer than that, use [rbaron]’s handy spreadsheet to choose larger batteries that last a whole year. Though, let’s hope we don’t have to spend another whole year inside with our plant friends.

We may never know why the weeds in the cracks of city streets do better than our houseplants, but hopefully, we can keep our green roommates alive (slightly longer) with a little digital nudge.