Wireless HVAC Sensors - V3 now available

At last we have it. V3 of my wireless HVAC sensor board has been tested and the hardware is done. There were some tweaks to the board over V2, one to fix a mis-routed trace and several geometric improvements to get it to fit inside an electrical box. And now all is well.

3D Printer Progress

Despite the lack of posts on the subject, progress is slowly being made on my 3D printer. A few months ago I got the structure pretty well flushed out in CAD. As sized in the model, this allows for something more than a 12 inch diameter build area. The height of the build is limited by how long I want to make the drive axes, in this version I targeted 12 inches tall.

Wireless HVAC Sensors - Part 2

Previously I introduced the idea of a battery operated wireless sensor board for sensing temperature and humidity. The intent is to get information to my Raspberry Pi (or Arduino, or any other microcontroller) so that it can intelligently control the HVAC system in my house. Today I give you an update on the project.

BLDC Hall Effect Sensors

So I've had two posts now where I talk about adding hall effect sensors to a BLDC motor. I figure it's time to explain a bit more how the process works.

This method only works with an outrunner style motor (that is, the rotor spins around the outside of the stator) with the magnets exposed on the underside of the rotor, such as this:

BLDC Motor Control

As part of my 3D printer project, one of the big electronics hurdles to overcome was a motor controller for a BLDC (BrushLess Direct Current) motor. Searching for a cheap, off the shelf controllers that would interface easily with a microcontroller turned up fruitless, so I took the opportunity to design my own circuit. It was a major project in itself, and while there's still a few hardware tweaks to make I'm quite happy with how it has turned out.

3D Printer Motor Control - Part 1

So I've been moving forward with my 3D printer plans slowly but surely. I've mainly been focusing on the drive axes up to this point, more specifically the details of controlling the motor. As outlined in my 3D printer post, I am planning on using closed loop position control with brushless DC (BLDC) motors, rather than the standard open loop control with stepper motors.

Wireless HVAC Sensors (temperature and humidity)

As I've been working to transition control of my HVAC systems over to my Raspberry Pi there has always been one big hurdle to overcome: how to I get the temperature reading from the room I'm interested in to the Raspberry Pi in the basement?

IR Remote Repeater

Last year I installed my TV on the wall. I really liked how it turned out, but I didn't like the look of cables running up the wall from my DVD player. So I put a recessed box behind the TV, routed the A/V cables through the wall and stowed the equipment in a nearby closet. It cleaned up the look of the room a lot, but there was a hurdle to overcome: how to I control the A/V equipment with a remote? I needed an infrared (IR) repeater to pick up the signal near the TV and repeat it in the closet where the media equipment is. I know there's commercial solutions to this problem, but I figured it would be easy enough to build my own.

Building a 3D Printer

I've decided to do it. I'm going to join the ranks of those who have a 3D printer in their homes. While having the ability to print custom parts for future projects will be a definite benefit, I must say that the lion's share of the fun will be in the making of it.

Now, I know there is no shortage of plans and designs available for DIY 3D printers contributed to by a community of makers, hackers, hobbyists, etc., I've decided not to go with an existing design. My schooling focused on robotic kinematics and control as well as mechanical design. It seems a shame not to put that learning to good use. Perhaps I'll blaze some new trails in the process.

Sous Vide Part 3: Advanced Development

In part 1 I introduced the concept of sous vide and why you should be interested in it. Part 2 covered a basic and low cost way to get your feet wet with sous vide. Today, part 3 will detail the more advanced stand alone controller I designed.

Sous Vide Part 2: The Early Version

In part 1 of this post I talked about what sous vide is and a little about how it can transform foods. I'm not going to delve into the world of opinions on how fantastic it is, unlocking unheard of flavors, tenderness beyond belief, etc etc. I assume that if you've come this far on the internet you've already read a lot about all that, so I don't need to convince you. Instead, I'll lay out my experience tinkering with my homemade controller, how I did it, and how you can do it, too.

Sous Vide Part 1: What and Why?

I was introduced to the concept of sous-vide cooking one day while listening to Science Friday. In a nutshell, sous-vide cooking involves vacuum packing your food (usually meats) and placing them into a temperature controlled water bath at lower-than-normal cooking temperatures for longer-than-normal cooking times.

Efficiently Reading Quadrature With Interrupts

Once you start wanting to control the position of a motor through feedback control, you will likely end up using a rotary encoder as the feedback device. Encoders can be broadly categorized as:

• Absolute position
• Incremental position

Absolute position encoders will tell you what the angular position is all the time, even between power cycles. Most use "grey code" (a modified form of binary) with several "tracks" (bits) to read position.

Incremental position encoders will tell you what the angular position is, but only relative to where it was when you started paying attention (usually on power-up). Two common types of incremental outputs are:

• Incremental (clever name)
• Quadrature

Incremental is rather useless for position control because it doesn't give you any information about what direction you are turning, just that you are turning. Quadrature encoders give you direction as well as incremental position. This article deals with efficiently reading quadrature output on an Arduino by utilizing external interrupts and some AVR bare-bones code.