Most of North America has been locked in a record-setting heat wave for the last two weeks, and cheap window AC units are flying out of the local big-box stores. Not all of these discount units undergo rigorous QC before sailing across the Pacific, though, and a few wonky thermostats are sure to get through. But with a little sweat-equity you can fix it with this Arduino thermostat and temperature display.
We’ll stipulate that an Arduino may be overkill for this application and that microcontrollers don’t belong in every project. But if it’s what you’ve got on hand, and you’re sick of waking up in a pool of sweat, then it’s a perfectly acceptable solution. It looks like [Engineering Nonsense] got lucky and had a unit with a low-current power switch, allowing him to use a small relay to control the AC. The control algorithm is simple enough – accept a setpoint from an encoder, read the temperature sensor, and turn the AC on or off accordingly. Setpoint and current temperature are displayed on an OLED screen. One improvement we’d suggest is adding a three-minute delay between power cycles like the faceplate of the AC states.
This project bears some resemblance to this Arduino-controlled AC, but it seems more hackish to us. And that’s a good thing – hackers have to keep cool somehow.
Continue reading “Arduino Replaces Bad AC Thermostat, Hacker Stays Cool”
It’s been said that hackers are enamored with complex networks. In the 60s and 70s, the telephone network was the biggest around, singing a siren song to an entire generation of blue-boxing phone phreaks. I started a bit closer to the house. As a child I was fascinated by the heating system in the basement of our home: a network of pipes with a giant boiler in the middle. It knew when to come on to provide heat, and when to kick on for hot water. I spent hours charting the piping and electrical inputs and outputs, trying to understand how everything worked. My parents still tell stories of how I would ask to inspect the neighbors heating systems. I even pestered the maintenance staff at my nursery school until they finally took me down to see the monstrous steam boiler which kept the building warm.
My family was sure I would grow up to be a Heating Ventilation and Air Conditioning (HVAC) tech. As it turned out, electronics and embedded systems were my calling. They may not have been too far from the truth though, as these days I find myself designing systems for a major manufacturer of boiler controls and thermostats.
Recently a house hunt led me to do some HVAC research on the web. What I found is that HVAC techs have created a great community on the internet. Tradesmen and women from all over the world share stories, pictures, and videos on websites such as HVAC-Talk and HeatingHelp.
Continue reading “HVAC techs – Hackers who make house calls”
It’s the rare tech worker that manages a decade in any one job these days – employee loyalty is just so 1980s. But when you started your career in that fabled age, some of the cultural values might have rubbed off on you. Apparently that’s the case for an Amiga 2000 that’s been on the job since the late ’80s, keeping the heat and AC running at Grand Rapids Public Schools (YouTube video link.)
The local news story is predictably short on details and pushes the editorial edge into breathless indignation that taxpayer dollars have somehow been misspent. We just don’t see it that way. “If it ain’t broke, don’t fix it,” is somewhat anathema to the hacker ethos. After all, there’s no better time to “fix” something than when it’s working properly and you can tell if you’ve done something wrong. But keeping an important system running with duct tape and wire ties is also part of the hacker way, so we applaud [Tim Hopkins] and his colleagues at the GRPS Facilities and Operations Department for their efforts to protect the public purse. And a round of applause is also due not only to the Amiga design team, who produced a machine that can run for nearly three decades, but also to Johnson Controls, whose equipment – apparently a wide area radio modem linking the HVAC systems in the district’s buildings – is being run by The Little Amiga That Could. Sounds like they built stuff to last way back when.
So when this machine is finally retired, here’s hoping they give it a good sendoff. Perhaps we’ll see it with some other Amigas at some future Vintage Computer Festival. Or maybe it’ll be one of those active retirees and start a career in the music industry.
[N8Mcnasty] is a HVAC tech who works on some big machines. One of his charges is a Carrier 19EX Chiller, rated at 1350 tons of cooling. 1 ton of cooling = 12,000 BTU. This particular chiller contained an odd LCD screen. It used a fiber optic bundle and a halogen light for backlight illumination. The system worked fine for over a decade. Now though, the halogen bulb has begun melting the glue on the fiber bundle, causing a dim display. The display in question shows some very important operating parameters, such as oil temperature, current draw, and process temperatures. Since they couldn’t easily see the display, the machine’s operators weren’t running the machine, placing stress on the other chillers in the building’s physical plant. [N8Mcnasty] tried repairing the bundle, however the glue kept melting.
A replacement display was no longer available, meaning that the entire chiller control system would have to be upgraded to a newer system. The new control system uses different sensors than the old one. This is where things start getting expensive. Replacing the sensors would also require draining the 15-20 gallons of oil, 4500 lbs of R134a refrigerant, and bringing the whole system down for almost two weeks, a $20,000 job. Rather than go this route, [N8Mcnasty] found an alternative. LED’s have come a long way since 1996, when the chiller was built. He simply replaced the halogen bulb with an LED and appropriate resistor. [N8Mcnasty] was even able to reuse the halogen bulb bracket. A bit of heat shrink tube later, and the fix looks like it was a factory option. He’s documented his fix here on reddit.
A while back, [Erich]’s oil heating system was due for a few repairs. Given the increasing price of fuel oil, and a few incentives from his Swiss government, he decided to go with a more green heating solution – geothermal heating. The system works well in the winter, but it’s basically useless in the summer. [Erich] decided to put his 180 meter investment to work for the summer heat, and made his geothermal heating system into a cooling system with a fairly low investment and minimal cost.
The stock system works by pumping cold liquid from [Erich]’s under floor heating into the Earth. In winter, the surface is always colder than the ground, thus heating [Erich]’s home. In the summer, the situation is reversed, with the cool earth insulated by the baked surface. All that was required to reverse the heating system was a few slight modifications to the heating controller.
Stock, [Erich]’s heat pump controller doesn’t have the capability to run the system in reverse, so he turned to a Freescale board to turn the compressor off and the pump on. With the additions, [Erich] is using 50 Watts to pump 1.5 kW of heat directly into the Earth below, a fairly efficient cooling system that’s basically free if you already have a geothermal setup.
[Viktor], one of our favorite avid hackers, has been playing around with 1-wire systems all this month. What started out as a MicroLAN Fonera has turned into an iButton interface, to a 1-wire powered hub, and finally a 1-wire character driven LCD. Anyone looking at 1-wire systems or OWFS could surely benefit from his testing.
However, if you still haven’t gotten your fill of 1-wire goodness, let us remind you of the 1-wire HVAC and IPv6 to 1-wire protocol translator.
The 1-Wire HVAC monitoring system is for residential Geothermal HVAC systems. This project utilizes the so called 1-wire temperature sensor. A single board computer handles the brunt of the work including web accessible trend data. With access to the underling temperatures, the over all system performance may be gauged. Earlier this year we covered a HVAC web enabled monitor that adds an element of control. As the industry adopts modern control architectures, we hope to see more HVAC hacks around.