Tuesday, October 30, 2012

You call that a recovery?

There has been a lot of talk about how there is finally an up real estate market. I have heard a whole lot of people try to tell me this is the lowest I am likely to see so I need to buy now. So here are a whole bunch of graphs of home prices over the past decade in the cities I am likely to end up in.

In Corona home prices increased 2% in the past year.
Corona Zillow Home Value Index

Fullerton did slightly better. Prices increased by 2.9%.
Fullerton Zillow Home Value Index

[La Habra](http://www.reddit.com/r/LaHabraCA/) was similar with a 2.3% increase in the past year.
La Habra Zillow Home Value Index

Hacienda Heights was 1.5%.
Hacienda Heights Zillow Home Value Index

Diamond Bar did slightly better with a 3% rise.
Diamond Bar Zillow Home Value Index

 Rowland Heights was 2.6%
Rowland Heights Zillow Home Value Index

Brea was 4% making it the highest value I saw.
Brea Zillow Home Value Index

Placentia was 3.8%
Placentia Zillow Home Value Index

Yorba Linda was 3.5%
Yorba Linda Zillow Home Value Index

And finally Chino Hills came in with no change over the past year.
Chino Hills Zillow Home Value Index

It is obvious by looking at these graphs that this recovery is over-hyped in this area. The rise in prices is tiny compared to the normal fluctuations in price. We have seen bigger bumps since the original crash which have quickly undone themselves.

It is safe to say that no home owner in this area has made money off their property investment in the past year. To make money the investment has to make more money than it costs to hold the investment. It has to beat maintenance, taxes, insurance, inflation and any interest the owner is paying on a mortgage. First of all, it takes a 2% return to match inflation, so several of the cities actually saw a decline in real prices. Then there is the price of interest. If you are paying 3.5% on a mortgage and only had a 3.5% down payment you will certainly lose money unless the property increases by a fair bit more than 3.5%. Then there is taxes, another 1% or so.

Still though, that is true in almost every real estate market. Thinking of real estate as an investment is the real problem there, it has almost never made sense as one. A better question is are you losing less money by buying than renting. With rents rising so fast in this area that may soon be the case. As someone in a cheap apartment, I don't see that being true for me soon though.

Monday, October 29, 2012

Pigeon Spy

This seems to be the month of interesting winged rats. Another use for pigeons is that you can strap small cameras to them.

This is a use for which they would now be much better suited for than in 1908. The quality of camera a pigeon can hold would be quite impressive. They don't fly so high up, so you should be able to get good quality pictures of the ground.

Spying on a facility would be easy. Train a few dozen birds to return to a facility a few hundred miles away from what you want to spy on. Drive to a few dozen sites on the opposite side of the facility and release a couple birds with cameras taking a picture every couple seconds. Assuming you camouflaged the camera well enough and made sure it couldn't be traced to you there is little risk of detection. Who checks every bird which flies over a facility for cameras? 

The birds also seem to have a history of use for smuggling drugs and other small objects.  This is harder. The problem is that not only can a pigeon not carry much weight, they only return to one location. So in order to smuggle drugs across a border or into a prison, first you would need to smuggle pigeons  the other way across the border or out of the prison.

Sunday, October 28, 2012

Another Three Phase Generator

After my previous attempt at building a three phase generator, it was clear that I could do a whole lot better. That was about the best I could do without using any real tools, but I have had a job long enough now that a shortage of tools shouldn't be stopping me from building more silly toys.

I also wanted to make a generator strong enough to run a motor. The first, and second simple generator I built and the previous three phase generator did not run motors well. So a few months back I started collecting parts for a new generator.

Once again I used the same website as inspiration, an excellent description of how to construct a three phase hand crank generator. The largest conceptual changes I made from his design were using transformer steel discs instead of powdered iron in epoxy for the cores and backing iron, and a Y connection for the coils rather than a delta connection which allowed me to have a four wire system rather than a three wire. I also have yet to match his belt drive which is really quite excellent.

The first step in making the generator was to make some coils. I decided to make 12 coils out of 24 gauge magnet wire. I simply wrapped the wire 100 times around a few of the one inch disc magnets I purchased for this project.

Then I procured a few sheets of transformer steel and a disc cutter. This cutter could make 7/8th inch circles out of the transformer steel fairly quickly. Unfortunately the transformer steel I got was really really thin. It took a very long time to make the several hundred discs required.

These discs were used to make 12 larger cylinders by gluing the discs together with JB weld. I also tried the JB weld steelstik shown in this picture, but it just dried too fast to be easily used so I ultimately gave up on it.

Next I wanted a backing iron. Essentially the idea behind both the steel cores, and the backing iron is the same. You want a path for magnetic fields to go from a magnetic north pole, through your cores, and to a nearby magnetic south pole, while entirely in transformer steel. Any gaps of air, or any other non ferromagnetic material will lower the efficiency. The cores and backing iron must be sheets of transformer steel (or powdered steel/iron) because if you use a large steel block eddy currents will flow in the steel sapping efficiency.  So I cut out about 10 squares of transformer steel to use for the backing iron.

I decided to use an 8in x 8in x 2in wooden block to support my generator. First I bought two ball bearings for the rotor to rotate on. One was placed on the top of the block, one on the bottom. Wood glue was used to hold them in place.

Next I attached the backing iron to the wooden block. The first two layers were wood glue in the hopes I could rescue the backing iron should the project be a failure. The rest of the layers were held together by JB weld. That did not seem like it would be strong enough so I also used four bolts with a large washer to hold the backing iron to the wood.

Once all the backing iron layers (approximately 10 layers) were in place I used JB weld to attach the cores. Placement of the cores was critical. They needed to be exactly the same distance from the center and have exactly the same angles between them. They also needed to line up exactly with the magnets on my rotor. Fortunately the JB weld takes several hours to dry, so I was able to get pretty good positioning.

Next I placed the 12 coils I made on the cores.

Then I soldered the coils together to produce three phases and a neutral. Understanding the wiring for this is difficult, and I cannot beat this explanation so I will not even try. Still, I should show how I wired this up, so I included the following sketch. The 12 coils are connected together into 3 groups of 4 coils which are wired together. Then one end of each of the 3 groups is soldered together to produce the neutral. The other end of each of the three groups is the phase wire.

Finally the rotor needed to be constructed. I used a saw blade for the base. It can be solid steel since it is not moving relative to the magnets and therefore will not have eddy currents flowing within it. I used JB weld to attach a washer to one side of the blade, placed a 5/16th inch bolt through the washer, and held several more washers on the other side with two nuts. Then the 8 magnets were placed an equal distance apart. They were set up so each one had the opposite pole up, so if one magnet had North Pole up, the two next to it would be South pole face up.

I put masking tape around the bolt to lock the nuts in place and because there would be less wobble in the bearings when I did so.

This generator has 8 magnets and 12 coils. This number of magnets and coils will produce three phases with peak voltages 120 degrees apart. By changing the number of magnets or coils it would be possible to make any number of phases, but I stuck with this since it matches what utilities use.

Lastly I bought some rubber feet for the bottom of the block and placed the bolt through the two bearings so the magnets are just above the coils. Here are some pictures of the final product.


Here is a video I took on my iphone of the generator connected to a cd motor. CD motors are Brushless DC motors, which are really just small three phase motors which are typically run on a small inverter. They will run just fine on the three phase power that this motor produces.

The generator produces about 5 volts (phase to phase) open circuit and short circuited will produce a half ampere of current. This isn't a lot of power, but it is enough for many basic demonstrations about how electricity works.

The biggest failure of this generator is that the air gap between the coils and the magnet is just too large. The problem is that there are 8 magnets each with a pull strength of about 12lbs. When they get close to the cores, the downward force on the rotor is about 100 lbs. More importantly, the upward force on my coils and backing iron is about 100lbs. Whenever I get much closer the cores seemed to break. That wasn't so bad since I could fix a few of them as they break, but some layers in my backing iron started to break which is hard to fix. Most likely this is the two layers I connected together with wood glue. Since the generator seemed to be working about as well as I wanted I decided to stop fiddling with closing that air gap, but I may take on that challenge in the future.

The other issue is that you just cannot spin the rotor very fast by hand. With a proper belt setup I could probably get the rotor to spin up at a thousand rpm or so. That would likely be capable of producing as much electricity as someone can make with a hand crank or perhaps be used on a small wind generator.

Friday, October 19, 2012

Avian Data Transfer

This quote from a wikipedia page amuses me:

In September 2009, a South African IT company, based in Durban, pitted an 11-month-old bird armed with a data packed 4GB memory stick against the ADSL service from the country's biggest internet service provider,Telkom. The pigeon named Winston took an hour and eight minutes to carry the data 80 km (50 mi). Including downloading, it took two hours, six minutes, and 57 seconds for the data to arrive, the same amount of time it took to transfer 4% of the data over the ADSL
Since data storage has increased so much in capacity, pigeons have become a much more practical tool for transferring data. It used to be that you could transfer a message a few hundred miles with one, but it wouldn't be more than you could fit on a page. Now, you could transfer all the data required to produce a stealth fighter on one bird. Given the huge population of feral birds this just might be the least likely message to be intercepted as well. I doubt a drone could track a bird even if it knew it had a message. The bird might get shot down, but only with a very determined effort.

Saturday, October 13, 2012

Ginger Beer Plant

I tried making beer a few times. I eventually just gave away everything and stopped bothering. While there were a few reasons for this, one of the primary ones was that it just did not make economic sense. I ended up spending about a dollar a beer in ingredients and putting in hours of work. It just made more sense to buy beer.

I was just given a "ginger beer plant" though which would have been a much better choice for a broke college student. The ingredients are pretty much just sugar, ginger, and ginger beer plant. This is astronomically cheap. Sugar at Target was 55 cents a pound. In bulk you can probably find a way to buy it for half that price. Assuming this uses the same amount of sugar as regular beer, I would guess that a 5 gallon batch would use about 8 pounds of sugar. Or about $4 for the batch. This works out to about 10 cents a beer!

Why this isn't in every dorm building in the country is beyond me.