Folding Parabolic Solar Cooker

I remember building my first solar oven when I was like 8 years old. It was pretty cool, in my eyes. It was just a cardboard box lined with mylar with a saran wrap cover. Just barely fit a cookie tray in it. It obviously worked best at noon when the sun was straight above us, since the walls of the box were straight. This design doesn't have that problem! It's meant to mimic a parabolic shape, the kind of shape satellite dishes are. This design catchs and focuses light pretty efficiently. The main difference between this design and others is that this folds up for portability! It was made from a cardboard box. Besides that all you need to build it is the mylar, some tape, and some string. You have to cut and fold it correctly first, of course. This is a really simple and cheap design that anyone could build half decently. Ours could be a little better, but I'll probably make more in the future. I'm not sure exactly where I found this design, but here's a site with the same one: http://www.angelfire.com/80s/shobhapardeshi/twelvesided.html. There are lots of other designs out there, some made from umbrellas!

It still needs some kind of stand to allow me to angle it toward the sun. Apparently a bucket works well but those aren't super portable. Even sitting like this mid day, it puts out quite a bit of heat. The main thing it's still missing is a stand to hold food. I'll need to build something light that can break down, but something strong enough to hold a pot full of water without it breaking and falling on the cooker and ruining it. That's a huge flaw with this design, is that if it gets wet, the cardboard can deteriorate and the whole thing falls apart. A solution to this could be to waterproof the cardboard with some kind of spray or lacquer after cutting but before applying the mylar. Another better solution would just be to make it out of something better than cardboard, somehow. Another thing that might help with this design is a saran wrap cover to trap some heat in there, but that could lead to melting the mylar or saran wrap. Also, you can see in the picture above that some of the mylar in the center is coming loose, which  happens from folding it up and breaking the tape holding the mylar on. A better design might use spray adhesive over the whole surface.

 It folds up pretty well! Could fit between your back and backpack, or on a framepack.

Knife Kit- Button Lock Folder DDR3-BL

This is my favorite knife for several reasons. It has a pretty sturdy build and firm lockup, it's beautiful, and I built it myself! Also my mother bought it for me freshman year of college. It has a 3.6" blade, Cocobolo scales, a button lock, and a safety lock. I think it's the classiest looking and feeling knife I've ever owned. The original safety lock was the only plastic part on the knife, so I cut and a filed a steel one out of a tiny piece of file scrap I had from a file knife I had made. The whole thing assembled super easy, except I had to cut the backspine to fit since it was made for the regular DDR3. I also polished the inside edge of the button lock because it kept getting stuck. We got the parts from www.knifekits.com, the same site I got the holstex I made my knife sheaths with that are shown in my other blog post.

I don't see these knives being sold finished very many places, and I almost sold this scratched up one on ebay for about what the parts cost (although I canceled the order...). The ones I see for sale are very customized and expensive. It could be fun to build customized ones and try to sell them. I think they're really cool looking, sturdy knives, and would love to see more of them out there. Knivekits.com has also always provided me with terrific service with all my orders and questions, and I'm glad to support their business!

This shows the custom backspine and safety lock I did. Super fancy! Just kidding. It would be cool to get some rat tail files and start doing filework though. The steel safety lock could use some work too to be honest, I actually filed it just a smidgin too thin and now it slides too loosely (it slides against the inside of the wood scales.

Measuring Specific Gravity without a Hydrometer

Basically, I'm lazy and cheap and haven't bought a hydrometer yet. It's also partly because I already have the stuff I need to measure the density of liquids. And I don't brew very often. If you're not familiar with brewing, measuring the density of liquids is useful for estimating the resultant alcohol concentration after brewing. Instead of buying a hydrometer to do this I just use a scale and a graduated cylinder. Admittedly, this is nowhere near as convenient as a hydrometer. In fact it's pretty fickle, and introduces more error by requiring two measuring instruments. But it seems decently accurate. My last cider measured in at 16% ABV, and it tasted and felt like it was 16%...

As an example here I have measured out 10ml off water in a small graduated cylinder. I don't use the tare function because it shuts off after like 20 seconds or something super annoyingly short. You can see below I have the weight before and after filling the cylinder. It's .01 grams under what it should be, so obviously this isn't perfect. But it's good enough for me. If you haven't figured it out, the density (or specific gravity) is the mass over the volume. To use this to find the alcohol concentration of a fermented beverage, measure the specific gravity before fermentation, and after fermentation. Subtract the ending SG from the starting SG and multiply it by 131. This is the approximate ABV! Basically you are measuring the amount of sugar that was converted into alcohol by the yeast. The sugar provided by your mash or wort increases the density of the water, but once its converted into alcohol, that lowers the density because alcohol is less dense than water. 131 is an approximate conversion factor. I don't know who figured that out or how.

If you forgot to measure the specific density before starting your brew, or your realized that the sugar you added at bottling for carbonation changed the density (like I did) then there are charts and smart people out there online that can help you estimate how much density different types of sugars will add to a brew. I've done this before. It introduces another vector for error, but I do that a lot apparently.

DIY Magnetic Stirrer

Another brewing post! I'm getting ready to brew some more beer and cider and I figured I may as well make one of those fancy yeast stirrers everybody uses. I actually made one of these back in high school but ended up salvaging it for the magnets, one of which ended up being used for retention in a knife sheath. I noticed I happened to have everything I needed to make another one so I cobbled this together. I used a dremel to cut out part of a fan blade so that I could have the magnets directly opposite each other and thus have the assembly balanced. I set them in place with Gorilla glue. For the power supply I used an old cell phone charger (actually the one I salvaged a microUSB tip from for the solar charger in my other blog post).

 

I used a metal lid from a Pierre Cardin box as the enclosure, or rather... a cover, since it's just sitting there. I haven't mounted the fan inside it yet, and I need to figure out the spacing before I do. It seems the magnets are too close to the stir bar. When the stir bar is further above the magnets, it spins fine, but when it is lower such as when it sits on the metal box, it can start to wobble and rattle. I think I might add in a thermoelectric plate on the top to add hotplate functionality. I also need a better power supply, this cell phone charger doesn't seem strong enough, and definitely won't be enough for the TEC.

It would be cool to drill out holes for a speed and heat control knob. It also might be cool to put a heatsink on the inside of the box, under the TEC and over the magnets/fan. Perhaps the TEC could be run in reverse for a... coldplate(?) effect. If the bottom can transfer enough heat through the box and off the heatsink by the fan so that it doesn't overheat, maybe the top can pull heat adequately from beakers holding exothermic reactions above it. But probably not. There's probably a reason nobody else does that. I'll just stick with an old fashioned ice bath for now.

Solar Charging my USB Backup Battery

I'm pretty outdoorsy, and I love to go camping. However I also love my electronics. Usually if I go camping I'll turn my cell phone off to preserve the battery, and actually put on my wrist watch for once to tell time for a few days. I usually end up turning it back on at some point or another, and it's always a guessing game wondering how long until the battery runs out. Some phones use up more energy when in a low signal area, draining their batteries even faster. About a year ago I bought a 10,400 mAh USB backup battery made by Bluetimes. It has two USB outputs, one of them with 2A output. I originally bought it to power my Odroid U3/Lapdock combo that I also have a post about. After I got rid of my Odroid I found it pretty handy to keep in my backpack for when I need to charge my phone or other devices, but don't have access to an outlet, or just when I forgot my charger. 10,400 mAh is pretty decent, but will only get you so far. That's where this comes in:

I've had this thing laying around for over a year now, I'm not even sure where I got it. They make much nicer ones these days with a battery pack build right in, but I can't afford that stuff! The problem was this cheap thing didn't come with a microUSB adapter... I've had it for a while but I don't know if they've updated the product or not. The good thing is it comes with alligator clips. So I just took an old cell phone charger, cut off the end, and stripped the end so I could hook up the alligator clips. Voila! A simple fix. I set it to 3v, 200mA, put the solar panel in the sunlight and the lights lit up on the battery, indicating it was charging! Although it's not charging as fast as it would off an outlet, it's better than nothing! Now I can recharge my backup battery on the go, and have a continuous, although small source of power when I'm camping. I'll probably solder over the wires soon so that I have something durable to clip onto, but otherwise I don't think it needs much more modification.

Secret Book Safe

Sometimes the best place to hide something is in plain sight. But usually it's not. However hiding something inside something else which is in plain sight can be a useful tactic. This one is pretty well known by now, but it's still somewhat useful. I wouldn't store my bitcoin private keys in this thing unless they were BIP38 encrypted. Gutting a book to use as a safe has probably been done as long as books have been around. But as long as there are still books, and you have at least a few for your book safe to blend into, it still works! Although to be honest it does seem physical books are starting to become a thing of the past. Anyway, here is what you need to make a booksafe:

• A book - take into account the size of the object you will be hiding as well as how much room you have to leave around the edges when you cut the book out
• A box cutter - these have a nice handle and are quite sharp, however once you get deeper into the book maneuverability becomes an issue
• An Exacto knife - the kind that have a pen like handle with a pointy blade at the end. This is essential for finishing it off, although you can't cut as many pages at once with it as the box cutter
• Some Elmers glue or other glue - experiment to find one that is less visible on the edge of a book
• Some common sense - please don't press too hard, then slip and hit yourself with the knife, and do this on a sturdy surface like a table. Don't ever cut toward your hard.

 While holding the front cover open, paint the edges of the pages in a thin layer of Elmers glue, then lay something heavy on the from page of the book (like another book) to hold it down while keeping the cover from getting stuck to the glue. Once it dries you may trace out the space you want to cut out, and begin cutting! I suggest using a box cutter for some rough work, followed by an Exacto knife type pen knife to finish it up. That's pretty much all there is to it! As you can tell mine is pretty sloppy, it's not hard to make them look better than mine.

How to Buy Bitcoin! (and get $10 for free)

There are a lot of questions to ask when you first learn about bitcoin. Who runs the whole thing? What is it "backed by"? How does it work? Why would I use it? But once people find good answers to these questions they're most important question usually ends up being, how do I get some?

Buying bitcoins can be easy, but it can also be pretty hard. It depends on a few things. Like where you live. Some services are only available to people in the United States. It also depends on if you have a bank account, or a debit card, or a credit card, or just cash. You can buy bitcoins in person with cash, but that has certain risks you have to be aware of. Buying them online from a reputable website is pretty safe, but most services require identity verification information and sometimes a several day wait.

Here are the services I've used:

Celery 
($10 free!)
http://gocelery.com/?r=65cc1fe9717f44689b2f832a0cdfc544
Celery sells and buys bitcoin, litecoin, and dogecoin. They conduct sales through ACH wire transfer, and it generally takes 5 days to receive your bitcoin after a purchase gets verified. Sometimes purchases don't seem to get verified for one or two days though, so that adds onto the total. When I signed up my account was verified the same day, however recently my friend signed up and had to wait 4 days to use his account. I guess they must be busy with new customers! Use my referral link above to get $10 off your first purchase of bitcoin, litecoin, or dogecoin! Get $15 worth for just $5!

Circle
www.circle.com
Circle sells and buys bitcoin. They can do ACH wire transfers, as well as debit and credit card purchases. Account verification takes 1-3 days in my experience and observation of my friends. Once you are verified you can make instant purchases with a debit or credit card, which is very convenient, however the fee is quite higher. You can also sell bitcoin on Circle and receive payment using a debit card instead of ACH, which means the money shows up the next business day. This is also very convenient, and can sort of lessen the worry of holding savings in bitcoin. For those like myself living on a tight budget, being able to immediately access all my savings easily can be important. Of course, the fee for selling with a debit card is higher as well, so it has it's caveats as well.

Coinbase
www.coinbase.com
Coinbase was the second site I used to buy bitcoin after bitinstant was taken down (google it). Account verification was very quick for me, but that was a while ago, so it may take longer these days. Coinbase conducts sales and purchases through ACH wire transfer, but also offers instant purchases with credit cards, but not debit cards (although some report it works for certain card types). With ACH it takes typically takes 5 days to receive your bitcoin.

Coinbase has received a lot of heat lately from users upset that Coinbase has been analyzing the sources and destinations of users bitcoin moving through Coinbase. For example, if you send bitcoin to or receive bitcoin from an address that Coinbase knows is associated with a gambling site, you may receive an email warning that your account will be shut down for continuing such activity. Also many people are starting to receive emails notifying them their account has been frozen, and they must provide explanations for the sources of the funds coming into the site in order to comply with anti-money laundering and know your customer laws. A lot of people find this contradictory to the spirit in which bitcoin was founded, and no longer support Coinbase because of this. While I'm not happy with their actions, I realize they are just trying to stay in compliance with regulations and to stay in business. It still sucks though.