You can view all of the construction pictures here.
The servos are where this project goes from information gathering to reacting. The first step is simply opening and closing dampers in various rooms as they need heat or cooling. Pretty simple idea, a little more difficult to implement then I thought.
I started off with a sheet of aluminium that I bought from home depot and cut that into smaller sections. I then outlined a servo on one end and cut out the hole with my Dremel. A few minutes under the drill press gave me the holes for the servo mounts and then I used a tap to put threads on those holes so they would take screws.
the servo mounts up pretty nice and is good and snug. I like the aluminium because it’s relatively strong and is very easy to machine without burning through tools. I bent the bracket on one side so it holds the joist a little better and then used my drill press to machine out all of the mounting holes.
I want a 1:1 ratio between the servo and the damper. That means that I need to have the center of the servo at the same point as the center for the damper. The arms also need to be the same length. Out comes the tape measure. The damper arm is right at 2.5 inches.
I had previously created the servo arms using aluminum square bar and some plastic spacers. Those worked ok, but the piano wire that joined the servo arm to the vent was a complete failure. A friend suggested I look into some RC hardware and that ended up being exactly what I needed.
The completed servo arm is nothing more then a pair of RC Car (traxxas to be specific) ball ends that I’ve threaded onto a piece of 4-40 all thread. The all thread is much stronger then the piano wire and it looks neat. It also gives me a little bit of flexibility when it comes to being able to rotate the ball ends to match up with mismatched angles.
The ball end screws on top of the servo and rests on the horn that came with the servo kit. I thought about using glue or plasti-weld or jb-weld to hold the arm onto the horn, and while those solutions would have worked, I didn’t like the way that they would have ended up looking.
Instead I bought some serious shrink tube from my local electronics recycler. This stuff is almost 3 times as thick as regular shrink tube and seems to have some sort of adhesive inside of it that activates when you heat it up. I used two layers of the tube and this thing is on very solid. I have to really work to get it to wiggle at all!
The arm and servo all mounted together looks nice and clean and is very functional. I also noticed that with the shaft so solidly mounted to the servo, I don’t have as much noise when the servo is actuated. Not that it was noisy before, but now it’s very quiet.
To connect the servo arm to the damper was fairly trivial. When the damper and the servo are parallel to each other, they are at just over 5 inches apart. so I just made a 5 inch bar with ball ends on each side and called it done. I have about 3/16 of an inch of play due to the way the two arms join together, but it’s effectively unnoticeable when it’s in use.
With the servo in the bracket and the bracket on the floor joist, it was a simple matter of using a screw and nut to bolt the ball end to the damper. Everything feels very solid and looks nice and clean. Servo actuation is excellent and the damper moves fairly smoothly.
Next: Pressure and Safety