When you think of a radiation detector, you’re probably thinking of a Geiger tube and its high voltage circuitry. That isn’t the only way to measure gamma radiation, though, and [Alan] has a great circuit to measure even relatively weak radiation sources. It uses a very small photodiode, and draws so little power it’s perfect for projects with the smallest power budgets.
The detector circuit uses a miniature solar cell and a JFET wired up in a small brass tube to block most of the light and to offer some EM shielding. This, in turn, is attached to a small amplifier circuit with a LED, Piezo clicker, and in [Alan]’s case a small counter module. The photodiode is actually sensitive enough to detect the small amounts of gamma radiation produced from a smoke alarm americium source, and also registers [Alan]’s other more powerful radioactive sources.
The circuit only draws about 1mA, but [Alan] says he can probably get that down to a few micoAmps. A perfect radiation sensor for lightweight and low power applications, and gives us the inspiration to put a high altitude balloon project together.
This is exactly what it looks like. [Oleg] calls it soldering in inert atmosphere, but it’s just a toaster oven reflow hack dropped into a container full of carbon dioxide.
Why go to this trouble? It’s all about solder wetting. This is the ability of the molten solder paste to flow into all of the tinned areas of a board. [Oleg] talks about the shelf life of hot air leveled PCB tinning, which is about six months. After this the tin has oxidized. It will certainly not be as bad as bare copper would have, but it can lead to bad solder joints if your PCBs are more than about six months off the production line. This is one of the reasons to use solder flux. The acid eats away at the oxidized layer, exposing tin that will have better wetting.
But there is another way. Soldering in the absence of oxygen will also help the wetting process. CO2 is heavier than air, so placing the reflow oven in a plastic container will allow you to purge air from the space. CO2 canisters are cheap and easy to acquire. If you keg your own homebrew beer you already own one!
Years ago we covered using thermite to destroy a hard drive. The idea is that if you melt through the platters, the data is completely unrecoverable. There are tons of videos of people doing this, but they all have a similar format. There’s a hard drive, with a flower pot or soda can sitting on top full of thermite. They then light this with a strip of magnesium and a torch.
I wanted to do something a little different. I wanted to implement thermite as a self destruct mechanism inside the device. To do this, I had to come up with a way to ignite the thermite. This stuff is very difficult to light. You have to get it really really hot. The easiest way is to use magnesium, which itself isn’t the easiest thing to light.
What I finally landed on was an ignition system that uses model rocket igniters, gun powder, and magnesium to light the thermite. The model rocket igniter can be set off from the 12v line inside your computer. However, it isn’t hot enough to light magnesium shavings, much less thermite. To get it to work, I needed to add some gunpowder. A small amount of gun powder would get hot enough to light the magnesium shavings, which in turn were hot enough to light the thermite. I had to be careful though, because too much gunpowder would cause a rapid expansion, blowing the thermite everywhere instead of lighting it. You can actually see some red thermite being blown out of the external hard drive and the laptop as the gunpowder ignites.
gun powder
model rocket igniters
magnesium shavings
Effectiveness of external hard drive self destruction:
I wasn’t sure about this one. There isn’t a whole lot of space for thermite and the ignition system inside the box. On top of that, the only space was at the side of the hard drive, where the walls are the thickest. I had no idea if the small amount of thermite I used would penetrate the drive. It did, just barely as you can see in these pictures. It looks as if it pooled in the screw holes and made it inside. The platters are damaged.
burnt unit
looking down on hard drive
you can see a hole in the drive from this angle
yuck
yep, appears to be the screw hole
platters are damaged, but not as effective as thermite to the top
Effectiveness of laptop destruction:
I decided to completely replace the cd rom with thermite. This gave me a ton of space to put things. I was pretty positive this would work. The hard drive is in the center of this laptop, which meant I had to place it on its side for this to be effective. You can see the thermite work its way down toward the drive in the video. As you can see in the pictures below, the drive cover is completely gone and the platters are destroyed. Success!
crusty
hard drive is center of the image
platters are clearly visible
completely fried
un covered
no data coming off that
Since this system can be powered by batteries or the internal power of your computer, it can be put inside a working device only to be used when needed. Obviously it is a ridiculous fire hazard that no one should bother with. It was a fun experiment though and I really feel like it is something that would fit in well in the world of [James Bond]
This lantern was built from recyclable goods. It’s a bit dangerous when used like the image above, but [The Green Gentleman] does give you a few other options in his build instructions which make for much safer operation.
The lantern enclosure is made from old cans and a glass jar. He screwed a couple of boards together at a right angle to act as a jig for cutting the glass. The V-shape created by the boards holds the jar on its side, giving his glass cutting tool something to rest upon. He then turns the jar to score it around the top, and then bottom. He alternated pouring boiling and chilled water on the score mark to shock the glass into breaking along the line.
This makes up the clear part of the enclosure which is later mated with metal top and bottom pieces. From there he adds either an LED, an alcohol lamp, or the Trimethyl Borate lamp seen above. The first two are relatively safe, but the latter burns at around 1500 degrees F. We have reservations about using a plain old glass jar as the enclosure for something burning this hot. It really should be heat resistant glass.
We’re surprised that we haven’t come across any of [Robert Murray-Smith’s] projects before. Looking through his collection of YouTube uploads proves that he’s a very active amateur chemist (we assume this is a hobby because he performs the experiment in a mayonnaise jar). The video we’re featuring today is about ten minutes of his technique for synthesizing graphene. The video can be watched after the break. Be warned that the audio doesn’t sync with the video because he overdubbed the presentation to fix up the poor audio quality from the original.
Graphene is something of a compound-du-jour when it comes to electronic research. You may remember reading about using DVD burners to make graphene film that will go into thinks like super-capacitors to replace batteries. [Robert] starts off his process with a jar of 98% sulfuric acid and 75% phosphoric acid. He pours in powdered graphite (chemical proportions are important here) and gives it a swirl. Next some potassium permanganate is added over about five or ten minutes. From there it goes on the stir plate for three days of constant stirring. During this time the solution will go from green to brown, indicating the presence of graphene oxide.
He goes on from there, but it’s clear he hasn’t found an iron-clad route to his end goal of isolating the graphene for use in constructing things like those super-capcitors we mentioned earlier. If you’ve got a home lab and some interest perhaps you can contribute to his efforts.
If you’ve ever used an extruding 3D printer, you know that the resulting prints aren’t exactly smooth. At the Southackton hackerspace [James] and [Bracken] worked out a method of smoothing the parts out using vapor. The method involves heating acetone until it forms a vapor, then exposing ABS parts to the vapor. The method only works with ABS, but creates some good looking results.
Acetone is rather flammable, so the guys started out with some safety testing. This involved getting a good air to fuel mixture of acetone, and testing what the worst case scenario would be if it were to ignite. The tests showed that the amount of acetone they used would be rather safe, even if it caught fire, which was a concern several people mentioned last time we saw the method.
After the break, [James] and [Bracken] give a detailed explanation of the process.
We think that anyone who’s done at-home PCB fabrication will appreciate the tidiness that [Fran] maintains throughout her etching process. She recently posted a three-part video tutorial which showcases her techniques. As you can see in the screenshot above, her habits reek of top-notch laboratory skills.
Regular readers can probably guess what circuit she’s etching. It’s the test boards for her LVDC reverse engineering. She is using the toner transfer method, but in a bit different way than most home-etchers do. She uses the blue transfer paper made for the job, but before transferring it to the copper clad she uses a light box (kind of like the X-ray film viewer at the doctor’s office) to inspect for any gaps where toner did not adhere. From there she uses a heat press to apply the resist. This is a heck of a lot easier than using a clothes iron, but of course you’ve got to have one of these things on hand to do it this way.
The second part of the tutorial is embedded after the break. We chose this segment because it shows off how [Fran] built her own chemical hood. It’s a clear plastic storage container lying upside down. A work window has been cut out of the front side, and a 4-inch exhaust hose added to the top. [Fran’s] lab has a high volume low velocity fan to which it connects to whisk the fumes outside.
