While dry ice can be obtained with simpler methods, for example by venting gaseous CO2 from fire extinguishers and collecting the forming CO2 flakes, [pabr’s] method is indeed attractive as a more compact solid-state solution. The setup employs a four stage Peltier element, which uses four Peltier stages to achieve a high temperature differential. With sufficient cooling on the high-temperature side of the element, it should be well capable of achieving temperatures below -78.5 °C, the sublimation temperature of CO2. So far, [pabr] has built three different setups to expose small amounts of CO2 to the cold of the Peltier element, hoping to observe the formation of little dry ice flakes.
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!
He starts of by discussing the various methods that are used to carbonate beverages. There’s the old yeast and sugar trick that takes place inside of a sealed bottle. But this takes time, and if you don’t calculate the mixture correctly you could have over or under carbonated bottles (or exploding bottles in the case of glass beer bottling). [Paul] himself has tried the dry ice in a cooler full of root beer method. The problem is that the cooler isn’t pressurized so the carbonation level is very low. You need to have cold temperatures, high pressure, and the presence of carbon dioxide all at the same time in order to achieve high levels of carbonation.
His solution is to use a 60 PSI safety valve. He drilled a hole in a plastic bottle cap to receive the valve. He then drops a few chunks of dry ice in and seals it up. The valve will automatically release the gas as the pressure builds past the 60 PSI mark. What he ends up with is a highly carbonated beverage in a matter of minutes.
[LokisMischief] wrote in to the tip line to let us know about this incredible home made CO2 laser. This thing is a complete DIY beauty, from the PVC cooling jacket to the toolbox based controller. The whole thing is essentially built from DIY parts, hand blown glass for the laser tube, plumbing store mirror mounts, a PVC cooling jacket with a caulked glass viewing window, and a neon sign transformer with a variac to control output. Even the optics are completely DIY, a hand drilled gold mirror and a NaCL window made from a polished chunk of icecream salt! [ThunderSqueak] says the control box only cost 60 bucks, and the rest of the parts don’t look too terribly expensive.
We could only find one video of the setup in the variac section of the site, and it was just a test the amp meter in the controller (no lasing anything at all). [ThunderSqueak] does make a note on the to do list about doing a good laser-y demonstration video, which we are looking forward to.
We’ve all been there. The day is done and it’s time for a cold one but you neglected to put more beer in the fridge after imbibing the last bottle the night before. You could chuck it in the freezer and revisit your attempt at refreshment in an hour. But if you need a malty beverage right now there’s no faster route than a beer chiller.
This particular beer chilling device is [Michael’s] entry in DEFCON 19’s Beer Chilling Contraption Contest. It can take a pint of beer from 90 degrees down to 45 degrees in just four seconds. Of course there’s a fair amount of setup time before you’re ready to use it. The device is a pipe within a pipe. The inner pipe houses the beer and the pipe surrounding it provides a containment area for a chilling liquid. [Michael] chose to use liquid carbon dioxide as a coolant because of it’s boiling temperature when under pressure. That is to say, the hottest part of the CO2 liquid is around the walls of the center pipe. By carefully dialing in the pressure of that outer chamber, the CO2 will boil away into gas as it cools the beer, making room for more liquid CO2 to contact the pipe and continue the cooling process.
The Pinewood Derby is a classic Cub Scout competition where dads and sons come together to build a small-scale race car. You start with a kit that includes a block of wood for the body, as well as four plastic wheels and four nails to act as axles. Most innovations in the ‘sport’ center around reducing friction between the wheels and the axles, and making the body as aerodynamic as possible.
This year [Sliptronic] grabbed an extra kit and threw the rules out the window by powering the car with compressed carbon dioxide. He used a 3D printer to make a housing for two CO2 cartridges that mounts on the center of the chassis. An official Pinewood Derby race track is on an incline and has a wooden gate that keeps each car in place until it is dropped to start the race. [Sliptronic] is using this gate as the triggering mechanism. Springs on either side of the car pull against an arm at the back of the vehicle. This arm is held in place by a rod protruding out the front of the vehicle. When the start gate is dropped that rod releases the trigger, which is pulled up by the springs to pierce the CO2 cartridges. You can see an overview of how that mechanism works in the video after the break.
[Rich] over at Evil Mad Scientist Labs took it upon himself to make eating fruit a little more enjoyable for his kids by infusing it with CO2 using his CO2inator. Observing the same principles used in making soft drinks and force-carbed beer, he decided to build a CO2 pressure chamber for use in his kitchen. He gathered a handful of easy to find components to construct his rig, including a household water filter housing and a CO2 cylinder from a paintball gun. He has some helpful hints for those who are not familiar with the process, noting that refrigerated fruit absorbs the gas more quickly than warm, and that considering the water content of the fruit is important when selecting what to carbonate.
Once [Rich] had everything safely connected and checked for leaks, in went the fruit. After about half an hour to an hour, the fruit was carbonated, much to the delight of his children. This looks like a quick and fun project for adults and kids alike, that can easily fit into a busy weekend schedule.