Rolling Your Own Furnace Controller

December 11, 2012 by Mike Szczys 17 Comments

replacement-thermostat

[Viktor’s] found an opportunity to put his embedded design skills to use when the furnace controller in his building went out. He admits it would have been much easier to just purchase a replacement, but not nearly as fun. Instead he built this furnace controller based on a PIC 18F4550.

First off, you may find it strange that we’re calling this a furnace controller and not a thermostat. But a study of the hardware schematic reveals that the device doesn’t have the ability to sense temperature. It merely switches the furnace on and off based on a time schedule. We guess this is for an apartment building where measuring the temperature at one central point doesn’t suffice?

At any rate, the build is clean and the UI looks quite easy to use. Inside there’s a board-mounted 12V relay which controls the furnace. The schedule is saved to the EEPROM of the microcontroller and time is kept by a battery-backed DS1307.

We’d love to see this extended in the future. Some possibilities would be adding internet connectivity and implementing a mesh network of temperature sensors which would give feedback to the main unit.

Open Source Android Thermostat

October 13, 2012 by Mike Szczys 39 Comments

Put that old Android phone to good use by mounting it on the wall as a smart thermostat. This open source hardware and software project lets you replace your home’s thermostat with an Android device which adds Internet connectivity and all that comes with the increase in computing power.

The brunt of the hardware work is taken care of by using an IOIO board which makes it easy to interface any Android device with the simple hardware which switches your HVAC equipment. We’ve been waiting for the launch of the new IOIO design and if it comes in at a lower price as has been rumored that makes this project in the price range of the least expensive of programmable thermostats (assuming you already have an Android device to devote to it). Simply etch your own board to host the relays and voltage rectifier and you’re in business.

There is a client and server app, both free in the Play Store. The server runs on the wall-mounted device with the client offering control via a network connection. The features of the system are shown off quite well in the video after the break.

This sounds like a perfect use for that phone you ripped out of the pages of a magazine.

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Getting A Nest Thermostat To Work In Europe

October 5, 2012 by Mike Szczys 24 Comments

[Julian] was really excited to get his hands on a Nest learning thermostat. It’s round, modern design will make it a showpiece in his home, but he knew there would be a few hiccups when trying to take advantage of its online features. That’s because [Julian] lives in Spain, and Nest is only configured to work in North America. But as you can see above, he did a bit of hacking to get it displaying his actual location.

The Nest is web-connected and phones home to the company’s server to handle configuration. Since they’ve made the decision to only support a portion of the world [Julian] had to do a little bit of digging to bend it to his will. He used Wireshark to sniff the packets it was sending. The calls to the company’s server use SSL, but the device also contacts the Weather Underground for data and this is not encrypted. So he was able to intercept that with his router and inject custom information. It’s not a full solution, but he’s part way there.

We’d really like to see what is possible with this device so please send us a link to any Nest hacks of your own.

Quieting An Inexpensive Bench Power Supply

March 29, 2012 by Mike Szczys 27 Comments

[Mike] just purchased this Atten APS3005S bench power supply for around $80. It does the job, but boy is it noisy! We were pretty surprised to hear it fire up in the video after the break. To make matters worse, the noise is persistent since the fan never shuts off. Having worked with other bench supplies he knew that a common feature included in many models is temperature controlled case fans. He set out to quiet the fan and implement a temperature switch.

For this project [Mike] had the benefit of looking at a nearly identical model that does have temperature switching. He discovered that the board on this one has a through-hole zero ohm resistor populated in place of a thermostat switch. That switch closes the connection at or above 45 degree Celsius, thereby turning on the cooling fan. Bridging the traces with a zero ohm resistor to save on production costs is what caused the fan to run continuously. After replacing the resistor with a KSD-01F and swapping out the stock fan for a high-quality version [Mike] has takes a noise maker and turned it into a device that’s kind to the ears.

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DIY Thermostat Keeps The Harsh Winter Cold At Bay

October 27, 2011 by Mike Nathan 13 Comments

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[Phil’s] parents grow their own organic food, but the harsh Ukraine winters make storing it a difficult proposition. Since it can drop to -30°C on occasion, they asked him to find a way to keep their storeroom at around 5-7°C above zero. He decided to construct his own programmable thermostat to keep things in check, and has been documenting the process as he goes along.

The thermostat uses a DS18B20 temperature sensor to monitor the room, and the logic is handled by an ATtiny2313. When the temperature dips low enough, the ATtiny triggers the room’s heater via a standard 240v relay. He can check the current temperature via a small 7-segment display mounted on the control board, which also contains three microswitches for controlling the heater.

It looks like a pretty solid build so far, and while he hasn’t finished coding the thermostat just yet, [Phil] says that those details are forthcoming. He has published a schematic however, so you can get a jump start on building your own if you’re looking to warm things up this winter.

Continue reading to see a video overview of the thermostat’s design.

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Building Your Own Replacement Refrigerator Thermostat

October 13, 2011 by Mike Nathan 34 Comments

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[Ron’s] refrigerator broke shortly after he came home from his weekly grocery trip, and since this was his second dead fridge in three years, he wanted to fix it rather than buy a new one…again. It turns out that the thermostat was toast, and a replacement would cost him $80. That was well more than he was willing to pay, but his groceries were starting to get warm, so he had to do something.

Being the tinkerer he is, he figured he could rig up his own thermostat that would work at least as well as the one that died on him. He scavenged an ATmega328 from a failed project, and after digging around online, put together the most barebones Arduino setup he could find. The microcontroller is tucked away in the back of the refrigerator where the old thermostat used to live, and takes input from a TMP36 temperature sensor, triggering a relay to start the refrigerator’s compressor whenever the the temp goes above 4°C.

[Ron] says his fix is just about the “worst kludge ever”, but as he saved $80 in parts and $150 in labor, we’re inclined to think it’s a job well done.

Server Room Light And Temperature Monitoring

April 27, 2011 by Mike Nathan 10 Comments

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[Jaren] is occasionally forgetful, and frequently wonders if he’s left the lights on in his server room. Not knowing if the lights have been left on drives him nuts until he returns to work the next morning, so he decided he had to do something. He figured it would be easy enough to build a small sensor that would allow him to monitor the status of the overhead lights, but he didn’t want to have his micro controller’s abilities go to waste by performing one simple task. Instead, he laid out plans to add an array of other sensors which will allow him to monitor the room’s temperature, sound levels, as well as the current draw of the servers.

Right now the project is in the beginning stages, but he already has part of his sensor network established. He hooked up a TMP421-based temperature module along with a TEMT6000 ambient light sensor to his Arduino, which displays the data on a small LCD screen he purchased. More sensors are on order, so we should expect to see more progress in the coming weeks.

Hopefully when everything is completed we will see a full set of schematics and code so that anyone can buld their own server room monitoring network from his designs.