Thursday, December 12, 2013

Project Bird Bath Heater - Update

Here are a few pics of the finished rectifier board:
Top

Bottom
I do plan on enclosing it in some type of box to protect it from the elements but first I want everything up and running.

For my rotating mount I decided to use the same thing I used on my prior mini windmill - a small caster wheel.

My first step was to pry of the plastic wheels:
Below is how I need to position it on the body of the windmill:
To attach it to the body I had to fashion 2 aluminum brackets (from a thinner piece of sheet aluminum - scrap I had left over from a previous project).  On the left in the picture below is one of the pieces that I used to shape and cut the brackets.
The final assembly, shown below, not attached to the windmill body.  The caster is inserted into a #4 rubber stopper which I used to attach it to the 3/4" conduit pipe (if you look closely you can see the line on the stopper where it met the top of the pipe) that I am using as the pole for the windmill.  With this arrangement I had to run the wires on the outside of the pole, which I was hoping to avoid.



Now on to the Heating Element

Since I couldn't find an adequate element I had to try and fashion one of my own from the nichrome wire harvested from an old hair curler.  I decided on using a 10cm segment wrapped around the mica like in the hair curler.  I then soldered leads taken from the hair curler (since they are insulated with heat resistant insulation) - to solder to the nichrome wire I needed to use an acid base flux.  Below is the wire wrapped around the mica with leads attached, the other mica above and below, and part of the aluminum case on the left:
For the aluminum case I again used a thin piece of sheet aluminum cut down to size - I designed it to be folded over the nichrome and mica bundle, with the sides wrapped around and the top flap folded over separating the 2 leads.  I rough cut the aluminum piece with a hacksaw and refined the shape with small metal files.
prior to folding edges over

ready for the epoxy
I sealed this shut using Loctite Epoxy Weld and soldered leads from the rectifier board to the element long enough to reach the bird bath.

Initial testing took place on Monday afternoon. After pounding a 3 foot galvanized steel pipe 1 foot into the frozen ground – I placed the windmills pole (10 feet long 3/4" galvanized conduit) into the steel pipe. With the wind blowing I tested the voltage across the heating element – I only saw values in the 10's of millivolts. Thinking something must be shorted I took it down and tested all the connections and all the diodes in the rectifier array. Everything was fine, it was only then that I realized that with such a low resistance almost all the voltage was passing through the element so the potential difference from one side to the other would have to be really low - so nothing was wrong and it was working correctly.  I set the windmill back up and placed the heating element in the bird bath and went back inside planning to check on it in an hour to see if any ice was melted.  When I came back to check on it the pole was up but the windmill was on the ground with its prop broken off the motor.  The high winds literally popped the stopper right out of the top of the pole.

I expected to post a wonderful success story but instead I need to back up, look at my assumptions and climb some additional hurdles to learn a bit more about a few things.

I am finishing up a new improved mount for the windmill and re-gluing the propeller to the stepper and hope to have it back up for testing tomorrow.