Thermo-Electric Coolers

OK, so I am living in a “Mother in law” sweet, which consists of a bedroom, a bathroom, a closet, and an outside door. A very nice place, right on the water, massive hedges grown into arches over the driveway. Very nice people, so natually I don’t want to bother them too much.

So I decide that I am going to get one of these fancy Thermo-Electric Coolers, basically an iceless cooler that you can plug into your car/the wall. They seem a bit handier then a small fridge (especially considering that I have one or two of those laying around in WI). It would seem to be useful after I get a different place to live – camping, hurricanes, etc.

I do my homework, and decide to get one. A little bit of online research shows me that all have this nifty feature that most people would consider “useless”, they are not only coolers, but they are warmers as well. Now, most people would go, why would I want my cooler to warm? Seems a contridiction. Well, I belong to a cooking club, and we get together once a month and see how cunningly we can poison each other. Actually, most everyone seems to be quite the accomplished cook, but I digress. Anywho, we seem to either overwhelm the fridge, or fight for the oven. I am thinking, “gosh, a place where we can keep things warm while people are getting settled, PERFECT, this little gadget is getting all the more usefull.”

So, superbowl sunday, I make a trip to the local Super Walmart at 5 oclock. I figured the entire male population is going to be sitting in front of the TV, and most of the women will be babysitting their boys. WRONG. Lesson 1, superbowl sunday, there is a run on coolers. Don’t expect to buy a cooler on superbowl sunday. They are all sold out. Lesson 2. I am apparently not the only freak who doesn’t watch the superbowl because the $15 worth of stuff I picked up required a 15 minute wait at the checkout.

Ok, so a few days later, I decide to start calling around. 4 phone calls locates 2 coolers like what I am looking for, or at least that is what my poor spanish and the dude on the other side of the phone poor english skills determine. So into the car I go. I get to Walmart, and look, and look, and look. No cooler, no blue Walmart vests. I finally find a cooler, EUREKA, it’s even the one I am looking for. The box is open, but a quick rummage reveals that everything is still there, so it must have been a superbowl “rentee”. Off to the checkout counter, 30 minutes later, I lug the thing into my car and drive home.

I get home, and dump it out of the box, I fiddle around and go to plug it in, but something is wrong. The online information said that to swtich between warm and cool, you flip the plug around on the cord as it plugs into the cooler. On MY unit, the cord goes straight into the cooler. Just my luck.

So, I decide to “fix” it. An hour on the internet reveals no significant information as to whether I can run the pelteir junction backwards without any damage, but one can deduce, that every OTHER cooler you can, as they allow you to do it. This warrents further investigation, so I dismantle my brand new cooler.

The picture shows the business end of a Thermo-Electric cooler. The small end on the right is what is inside the cooler, and the large end on the left is outside. You can see a thermal disconnect strapped to the outside heatsink. There is no thermal monitoring on the inside. This means that I could really have some fun, melting my new cooler.

Short term plan, get a double pole, double throw switch, and install it so that I can switch the peltier unit to heat/cool. This I think is a great improvement on how the other cooler/warmers work in that the fans will always run in the more effecient direction. I just need to remember not to leave the unit on heat overnight or I may do some serious meltage damage to my brand new cooler.

Long term plan, install my own thermal regulater on the inside of the cooler. Now I COULD go out and get one like what is already installed for about $3.00. That just isn’t any fun. Being a out-of-practice electronics hobbiest, I am going to install an embedded microcontroller to control my fancy cooler. The one I have at hand happens to be eithernet enabled. So I think I am going to have the only Internet Cooler in existance.

I am thinking that I am going to install a total of 4 temperture probes (simple thermisters) to monitor ambient outside temperature, outer heatsink temperature, inner temperature, and inner heatsink temperature. I will log these temps at 15 minute intervals, and create graphs. A batter backup for the controller means that I can continue to log temperature even when the cooler is unplugged/without power, whatever. I will then be able to log into my cooler, and get the current stats on whether my milk has gone bad or not because the temp is too high.

I think I am also going to install a digital temp readout on the outside of the cooler so that I know what temp it is without having to go online (handy during a hurricane when the internet is down).

The switch will be repurposed into telling the microcontroller whether it should heat or cool. I think this is a wise move, as some of my “friends” may try to hack my cooler and switch it from cool to heat and spoil my milk. The hardware switch saves me the expense of mailing said spoiled milk to my “friend” and having him deal with the stench he created.

What do you think? Posted by Picasa.

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