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Peltier Cooler

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I have this small wine-refrigerator that is both old and not working.  I don’t really need it, but it’s nice to keep extra beers and wine in there.

My idea is to get a peltier cooler and convert this from a compressor cooler to a solid state cooler.  Of course it won’t be as efficient or cold – but as long as it gets just a little bit cooler I will be happy.

I ordered some coolers online (they weren’t super expensive) and they seem to work. It requires 12 volts and up to 5 or 6 amps – so the power supply might be an issue (it seems many people use a computer ATX power supply).  Actually, you can just connect it to a D-cell battery and put your fingers on each side of the cooler and easily feel a temperature difference (great for demos).

With a temporary power supply, I put the cold side of the peltier on a big aluminum block and then I put a cpu heat sink on the hot side.  This didn’t work – but here is a picture.

IMG_4732.jpg

It turns out that the peltier cooler gets hot – but it keeps a temperature difference between the two sides.  So the key is to keep the hot side as cool as possible.  With this in mind, I switched it so that the hot side was on the block and there was nothing on the cool side.  I still didn’t work very well until I put some thermal paste between the peltier and the aluminum block for good thermal contact.

Here is what I get.

Pretty cool, right?

I will keep you updated.

Bonus: Fixing a Kenmore 44072 Washer with F03 Error

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This is not a “fix-it” blog. However, I think the Internet should be a useful friendly place. Think about the times you have had a problem. The Internet has been there for you – right? I remember not too long ago, I was trying to set up iChat video chat with my brother-in-law and his brand new iMac. I was 3 states away and it was getting frustrated. In the end, my friend the Internet helped me. Problem solved. Everyone one has found a perfect solution for a particular problem on the Internet – right? So, this bud’s for you Mr. Post-obscure-stuff-in-the-hopes-that-at-least-one-person-finds-it-useful guy. Right. So, this isn’t really physics or science like my normal stuff.

Here is my washer. It makes my family happy. They like clean clothes. Kenmore 44072 Front Load Washer.

Well, my wife went to wash clothes and the front display says F03 Error. Me: ER? So, I look it up on the Internet. Here is the site I found from [fixya.com](http://www.fixya.com/support/t629840-kenmore_44072_front_load_washer_drain). Ok, it appears it could be something stuck in the drain hose. There was definitely water in there. I tried a couple of things, but finally decided to take off the back of the machine and look inside (unplug it first). I followed the hose to the pump and there is this squishy rubber bag connected to the pump. I squeezed it and sure enough, something was in there.

It wasn’t trivial to get all the water out of the machine without the pump. At first I lowered the drain hose into a cup a little at a time. Finally, I hooked my wet-dry shop vac up to the hose and sucked the water out. (everyone needs a wet-dry shop vac). Anyway, I took off the “pump bag” – not sure what it is called, but here is what it looks like:

![Screenshot 50](http://blog.dotphys.net/wp-content/uploads/2008/10/screenshot-50.jpg)

The pump bag had one of those annoying metal clamps holding it on – you can see the same kind holding the drain hose to the pump. When I removed the bag, more water came out. Here you can see something stuck in the pump.

![Screenshot 51](http://blog.dotphys.net/wp-content/uploads/2008/10/screenshot-51.jpg)

I pulled that sucker out. Here is the stuff I found:

![Screenshot 52](http://blog.dotphys.net/wp-content/uploads/2008/10/screenshot-52.jpg)

I put everything back together, and it seems to work. Do not ever try this. Don’t ever open your washer. Don’t try to fix things. See, I told you NOT to do that. It’s dangerous, you could break something. (now you can’t get angry if something goes wrong).

Fun things to do with a green laser pointer

rhettallain 1 Comment

I went home for lunch today. While waiting, I saw this lizard. We have many lizards in Louisiana, I like them, really I do. So, this is what I did:

No lizards were harmed in the filming of this video.

I was really surprised. I thought for sure that I had tried this before and nothing happened. Maybe it was because of the white surface the lizard was on. Maybe it was because it was an older and wiser lizard (it was larger than normal). Maybe this is already a well known fact about lizards and laser pointers. Needless to say, this was quite entertaining and completely justifies the cost of my laser pointer.

Letter to High School Students: What to Major in

rhettallain 2 Comments

Dear High School students,

How are you? I am fine. I am very glad that I am no longer in high school. Maybe you enjoy high school, but for me, it was not so good. Don’t get me wrong, I went to an excellent high school (Waubonsie Valley HS). There was something in high school that didn’t feel right. Maybe it was being in classes for too long and the lack of time to work on my own projects. Maybe it was lack of freedom in choosing my own classes (there was some freedom to chose). Or perhaps I was just not mature enough to enjoy it. Needless to say, I am past that now.

I think now, how could I help high school students? In particular, how could I help them choose a major in college (if they choose to go to college). So, this will be the topic of this letter today. Please don’t hope that I will write more useful high-school letters such as “how to find a prom date”. That is definitely one area I failed at.

Choosing a major is difficult and even scary. In a way, you are choosing a career – but maybe not as much as you think. First, choosing a major is somewhat a random event. Suppose you choose underwater basket weaving as your major for some reason. It is likely that you have never woven a basket underwater. Maybe you will like it, but maybe you won’t. You won’t really get a good idea of how much you like or dislike underwater basic weaving until you actually go underwater and weave a basket. Unfortunately, the underwater basket weaving curriculum has you taking UBW 101 (Introduction to underwater basket weaving) your sophomore year. You first have to take the pre requisites, history of baskets and introduction to water. After you decide you don’t really like this major, it has already been 1-2 years. So, if it takes you 5 or 6 years to graduate, don’t worry TOO much. Your parents may be displeased, but tell them I said it was ok.

**Major in Physics**

I know. You saw that coming. Why should you major in physics? Here are some of my points:

**It is difficult**

Wait. BECAUSE it’s difficult? Shouldn’t you do something because it is easy – not difficult? Well, it depends on why you are doing it. If you are doing something to improve yourself, difficult is good. Imagine you were going to exercise. Should you walk around the block or run 3 miles? Well, if you find that walking around the block is very easy, it probably won’t do much for you. If you find underwater basket weaving to be easy, maybe it is not really helping you grow. So, physics IS difficult, but that is a good thing.

**What else are you going to do?**

I hate to be a negative person (I am not really) but look at where we are today. There are financial problems, energy problems, problems with that rick-roll stuff. What are we going to do? You could help. Maybe it will be you that contributes to the energy problem (well, we all contribute to the problem, maybe you could contribute to the solution). Physics gives you are start in the fundamentals of nature. We NEED people to understand the basics so that we can defeat the energy problem.

What are your other options? Underwater basket weaving? Maybe there are lots of people who can do underwater basket weaving. This means there are lots of people capable of UBW (underwater basket weaving). Job competition for UBW is high and maybe companies will just start sending their UBW tasks to India where it costs less. Plus, does anyone really NEED UBW? Maybe it is the first thing to go when the economy is taking a turn for the worse.

**Are you ready for physics?**

A common idea that comes up is that students think they can not major in physics because they did not take physics in high school. I don’t think this is a disadvantage in any way. In introductory physics, the common problem is that students must “*unlearn what they have learned*” such as the idea that *constant force causes constant motion* (just to be clear -that idea is wrong). What about math? Yes, you need to be proficient in math. Most students entering school (at least here) are not quite where they need to be in terms of math understanding. However, that doesn’t mean they can’t catch up. Ideally, students should be ready to take Calculus I when entering college. You have time, work on your algebra and trig skills so that you can do well on the Math part of the ACT and place into Calc I.

**Other**

This is longer than I usually write without including an equation, so maybe this is a good place to stop. If you want to major in physics, there are lots of things to consider. Here are some resources:

LaTeX equation test

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I use equations quite a bit. What I have been doing is writing the equations in LaTeX and then taking a screen capture of the output. I think this makes nice looking equations, but it sure takes a while. Here I am testing [LaTeX for WordPress plugin](http://wordpress.org/extend/plugins/latex/). The following *should* be some equations:

$$\vec{F}_\text{net}=\frac{d\vec{p}}{dt}$$

$$a^2+b^2=c^2$$

End of test. This was only a test. Had this been a real post, it *might* have had something useful.

**update** not sure if I like the way the equations look.

People in and out of a bar

rhettallain 1 Comment

So, I am still in Alabama because of lack of electricity in Louisiana (although we got power back last night – YAY!). My wife convinced me to go out and hear this band since we are staying at my parents and they said they would watch the kids. In general, I am way too old and crotchety to go out – but it appears I had no choice. Overall, it was not too bad except for staying out too late. (the band was actually pretty good – I think they were called [Fly By Radio](http://www.fly-byradio.com/) and they played 80s musics) The one thing I thought about while in the bar was the long line of people waiting to go in. At some point, the number of people inside reaches its maximum capacity. People still come in because some people leave. Here is my rough sketch of this: (I call it a bar graph – get it?)

![bar graph](http://blog.dotphys.net/wp-content/uploads/2008/09/bar-graph.jpg)

My first idea was to think of the bar as a capacitor and maybe this works. Ok, now I made something positive out of my trip.