Arduino Thermostat Includes Vacation Mode

When [William’s] thermostat died, he wanted an upgrade. He found a few off-the-shelf Internet enabled thermostats, but they were all very expensive. He knew he could build his own for a fraction of the cost.

The primary unit synchronizes it’s time using NTP. This automatically keeps things up to date and in sync with daylight savings time. There is also a backup real-time clock chip in case the Internet connection is lost. The unit can be controlled via the physical control panel, or via a web interface. The system includes a nifty “vacation mode” that will set the temperature to a cool 60 degrees Fahrenheit while you are away. It will then automatically adjust the temperature to something more comfortable before you return home.

[William’s] home is split into three heat zones. Each zone has its own control panel including an LCD display and simple controls. The zones can be individually configured from either their own control panel or from the central panel. The panels include a DHT22 temperature and humidity sensor, an LCD display, a keypad, and support electronics. This project was clearly well thought out, and includes a host of other small features to make it easy to use.

Raspberry PiPhone Thermostat Monitors Your Entire House — Or At Least That’s The Plan

[Jeff McGehee] or how he likes to be known, [The Nooganeer] just finished his first big tech project after finishing grad school. It’s a connected thermostat that makes use of his old iPhone 4, and a Raspberry Pi.

Ever since [The Nooganeer] bought his first home with his wife back in the spring of 2014, he’s had ever consuming dream of adding home automation to every appliance. As he puts it…

Home automation has always been a fascination of mine.  How much time and irritation would I save if I didn’t have to worry about turning things on and off, or wonder in which state they were left?  How much more efficient would my home be?  Wouldn’t it be cool to always know the state of every power consumer in my home, and then be able to record and analyze that data as well?

His first challenge was making a smart thermostat — after all, heating and cooling your house typically takes the most energy. Having used a Raspberry Pi before he figured it would be the best brain for his system. After researching a bit about HVAC wiring, [The Nooganeer] settled on a Makeatronics Solid State Relay board to control the HVAC. This allows him to use the GPIO’s on the Raspberry Pi in order to control the furnace and AC unit.  Continue reading “Raspberry PiPhone Thermostat Monitors Your Entire House — Or At Least That’s The Plan”

Chinese Temperature/Humidity Sensor is Easily Hacked

There’s a new piece of electronics from China on the market now: the USR-HTW Wireless Temperature and Humidity Sensor. The device connects over Wi-Fi and serves up a webpage where the user can view various climate statistics. [Tristan] obtained one of these devices and cracked open the data stream, revealing that this sensor is easily manipulated to do his bidding.

Once the device is connected, it sends an 11-byte data stream a few times a minute on port 8899 which can be easily intercepted. [Tristan] likes the device due to the relative ease at which he could decode information, and his project log is very detailed about how he went about doing this. He notes that the antenna could easily be replaced as well, just in case the device needs increased range.

There are many great reasons a device like this would be useful, such as using it as a remote sensor (or in an array of sensors) for a homemade thermostat, or a greenhouse, or in any number of other applications. The sky’s the limit!

Custom Raspberry Pi Thermostat Controller

Thermostats can be a pain. They often only look at one sensor in a multi-room home and then set the temperature based on that. The result is one room that’s comfortable and other rooms that are not. Plus, you generally have to get up off the couch to change the temperature. In this day and age, who wants to do that? You could buy an off-the-shelf solution, but sometimes hacking up your own custom hardware is just so much more fun.

[redditseph] did exactly that by modifying his home thermostat to be controlled by a Raspberry Pi. The temperature is controlled by a simple web interface that runs on the Pi. This way, [redditseph] can change the temperature from any room in his home using a computer or smart phone. He also built multi-sensor functionality into his design. This means that the Pi can take readings from multiple rooms in the home and use this data to make more intelligent decisions about how to change the temperature.

The Pi needed a way to actually talk to the thermostat. [redditseph] made this work with a relay module. The Pi flips one side of the relays, which then in turn switches the buttons that came built into the thermostat. The Pi is basically just emulating a human pressing buttons. His thermostat had terminal blocks inside, so [redditseph] didn’t have to risk damaging it by soldering anything to it. The end result is a functional design that has a sort of cyberpunk look to it.

[via Reddit]

Wax Motors Add Motion to Your Projects

[electronicsNmore] has uploaded a great teardown and tutorial video (YouTube link) about wax motors. Electric wax motors aren’t common in hobby electronics, but they are common in the appliance industry, which means the motors can be often be obtained cheaply or for free from discarded appliances. Non-electric wax motors have been used as automotive coolant thermostats for years.  Who knows, this may be just what the doctor ordered for your next project.

As [electronicsNmore] explains, wax motors are rather simple devices. A small block of wax is sealed in a metal container with a movable piston. When heated, the wax expands and pushes the piston out. Once the wax cools, a spring helps to pull the piston back in.

The real trick is creating a motor which will heat up without cooking itself. This is done with a Positive Temperature Coefficient (PTC) thermistor. As the name implies, a PTC thermistor’s resistance increases as it heats up. This is the exact opposite of the Negative Temperature Coefficient (NTC) thermistors we often use as temperature sensors. PTC’s are often found in places like power supplies to limit in rush current, or small heating systems, as we have in our wax motor.

As the PTC heats up, its resistance increases until it stops heating. At the same time, the wax is being warmed, which drives out the piston. As you might expect, wax motors aren’t exactly efficient devices. The motor in  [electronicsNmore’s] video runs on 120 volts AC. They do have some advantages over solenoid, though. Wax motors provide smooth, slow operation. Since they are resistive devices, they also don’t require flyback diodes, or create the RF noise that a solenoid would.

Continue reading “Wax Motors Add Motion to Your Projects”

Very Dumb Security For a WiFi Thermostat

We have finally figured out what the Internet of Things actually is. It turns out, it’s just connecting a relay to the Internet. Not a bad idea if you’re building a smart, Internet-connected thermostat, but you have no idea how bad the security can be for some of these devices. The Heatmiser WiFi thermostat is probably the worst of the current round of smart home devices, allowing anyone with even a tiny amount of skill to control one of these thermostats over the Internet.

The Heatmiser is a fairly standard thermostat, able to connect to an 802.11b network and controllable through iOS, Android, and browser apps. Setting this up on your home network requires you to forward port 80 (for browser access) and port 8068 (for iOS/Android access). A username, password, and PIN is required to change the settings on the device, but the default credentials of user: admin, password: admin, and PIN: 1234 are allowed. If you’re on the same network as one of these devices, these credentials can be seen by looking at the source of the webpage hosted on the thermostat.

if you connect to this thermostat with a browser, you’re vulnerable to cross-site request forgery. If you use the Android or iOS apps to access the device with the custom protocol on port 8068, things are even worse: there is no rate limiting for the PIN, and with only four digits and no username required, it’s possible to unlock this thermostat by trying all 10,000 possible PINs in about an hour.

There are about a half-dozen more ways to bypass the security on the Heatmiser thermostat, but the most damning is the fact there is no way to update the firmware without renting a programmer from Heatmiser and taking the device apart. Combine this fact with the huge amount security holes, and you have tens of thousands of installed devices that will remain unpatched. Absolutely astonishing, but a great example of how not to build an Internet connected device.

Energy-Saving Fireplace Thermostat

[Andrian] has a boiler stove that heats water and sends it to a radiator. As the fireplace heats the water in a boiler a temperature sensor opens the a valve to send the warm water to the radiator. The radiator sends its cool water back to the boiler to be reheated. The valve is slow, so before the boiler can send all the water to the radiator, it’s getting cool water back causing the valve to close while the heat is built back up. To prevent the valve from working so hard and wasting energy, [Andrian] designed a better thermostat to control the valve operation.

The thermostat uses one LM85 temperature sensor to check the water in the boiler and another one for the ambient temperature. Once the boiler water reaches the desired temperature, the valve is opened via relay. The system waits for half an hour and then checks the boiler temperature again. The brains of this operation is an ATMega168 with a 32.768kHz crystal as the RTC. Code and PCB files are available in his repo.

We love to see these types of hacks that challenge the status quo and increase the efficiency of appliances. We applaud you, [Andrian], for turning your dissatisfaction into a positive plan of action and for sharing your experience with the rest of us!

If you want to up the eco-friendliness of heating water a bit, you could heat the water with a compost heap.