Behold the uWave, a microwave oven that plays YouTube videos while it cooks. [Kevin] and three classmates at the University of Pennsylvania developed the project for the 2011 PennApps hackathon. It uses a tablet computer to replace the boring old spinning food display microwaves are known for. Now, an Arduino reads the cook time and sends that information to a server via its Ethernet shield. The server then searches YouTube for a video that approximately matches the cooking time, then pushed that video to the tablet to start playing. The video demonstration embedded after the break shows this, as well as the tweet that the machine sends at the beginning of the process.

It’s an interesting concept, and we think the code used to push a video to the tablet has a lot of other applications (we’re keeping this one bookmarked). On the other hand, we wonder how long it will take for public microwaves to become ad-supported? We’re thinking it’s hard for companies selling antacids, acid reflux medicine, Cup ‘o Soup, and Hot Pockets to resist this opportunity.

Instructables user [Rohit] had an out-of-warranty microwave with a broken membrane keypad. Much like our friend [Alexandre] from Brazil, he found the cost of replacement parts beyond reasonable, so he had to find a way to repair it instead.

He disassembled the front cover of his microwave to get at the main controller board. Once it was detached, he removed the keypad’s cover to get a closer look at the matrix underneath. While taking notes on how the matrix was wired, he found that some keypad traces connected to other traces rather than buttons. He says that they are likely used by the microwave to detect that the keypad is present, so he made sure to short those traces out on the controller board when he wired everything back together.

He replaced the aging keypad with microswitches, but rather than mount them on the front panel of the microwave, he drilled holes for each switch so that he could mount them inside the face plate. Once everything was wired and glued in place, he re-mounted the keypad’s cover. Now the microwave looks stock but has firm, reliable, user-serviceable buttons that are sure to last quite a while.

[Alexandre Souza] needed a microwave pretty badly, but he didn’t have a lot of cash on hand. He located one for a great price, but once he got home he found that things weren’t working quite like they should be (Google translation).

After some investigation, he narrowed the problem down to a bad keypad membrane. Unfortunately for him, this model of microwave was never sold in Brazil (who knows how it got there) and the only membrane he could track down had to be shipped in from the US at a cost of $80.

Rather than pay such a high price for a simple membrane, he opted to fix the microwave himself. He dismantled the control panel and thoroughly traced the keypad matrix to get an understanding of which pins toggled which functions. With a piece of protoboard and almost two dozen push buttons in hand, he built his own keypad and wired it directly into the microwave’s control board.

With labels written in marker it might not be the nicest looking thing you have ever seen, but it works a treat and is a great money-saving hack.

Instructables user [Jimmy Neutron] had an old microwave sitting around and figured he might as well gut it to build a high-energy radio frequency (HERF) gun.

The concept of a HERF gun is not incredibly complex. Much like your microwave at home functions, a high voltage power source is used to drive a magnetron, which produces micro wave radiation at 2.45GHz. These waves are then guided away from the magnetron using a waveguide, towards whatever the target might be. These waves then energize the target in a similar fashion as the water molecules in your food are energized during cooking.

[Jimmy] has not quite finished his HERF gun as he still needs to build a waveguide for it and then safely mount it for use. In the meantime, check out the pair of HERF guns we found in the videos below.

As a parting note, we must stress that building a similar device is dangerous, very dangerous – especially if you do not know what you are doing. Microwaves contain high voltage components, and exposure to microwave radiation can be deadly under certain circumstances. Stay safe!

Looking for more microwave fun? Check these out!

We know way too little about this subject but hopefully [Bob4analog] helped us learn a little bit more this time around. He’s building his own linear amplifiers on what looks like sheets of MDF. This is an evolving design and the two videos after the break show two different iterations. He’s salvaged several components, like transformers from microwaves, as well as built his own components like the plate choke to the right of the tubes in the image above. In standby, the amp sits at 2800 volts, warming the filament before the unit is switched on.

So what’s he got planned for this? Good question, but it appears that there’s more than enough power to drive a long-range transmitter.

First iteration: two tubes

Second iteration: single tube

[via Make]

[Jake's] projects have become regular features here on Hack a Day. He keeps the Halloween hack-fest rolling with his Flying Crank Ghost. For the ghost he used a store-bought skull but sculpted some hands himself out of Styrofoam. The body is fashioned from coat hangers with a bit of creepy fabric draped over the hole thing to complete the look.

He added some very convincing motion to the ghoul using a salvaged microwave turntable motor. The motor is mounted in the center of a two crossed boards, and has an armature attached to it. Three strands of monofilament attach to the end of the armature, run through eyelets on the ends of the crossed boards, then attach to the head, and each arm. When the motor is turned on, the armature turns, moving the head and hands up and down at different rates. Take a look at the embedded video after the break to see the final product.

[Jake] does mention that the motor he used is a bit underpowered. We figure this only needs to hold up for one night, so dig through your junk bin and see if you can throw one of these together in a few hours.

Spot welders are used in the fabrication of automobiles, PC cases, power supplies, microwave ovens, electrical junction boxes, Faraday cages, and various electronics. A spot welder is used because it produces a highly defined point of contact weld. The materials are welded without excessive heating, so working pieces are handled easily. The weld is also highly controlled and repeatable. In this how-to we cover the basics of a spot welder, and then show you how to build one from a microwave oven transformer.

A spot welder’s electrodes serve at least three functions. They transfer electrical energy to the material while also holding it together; this also controls resistance. The greater the pinch force the less the resistance, which results in decreased resistive heating. A lesser pinch force results in increased resistive heating. The electrodes also conduct heat away from the material, while in the off cycles, helping to cool and temper the weld. A resistive spot weld is commonly referred to as a ‘nugget’. Spot welders are generally confined to ferrous materials which somewhat limits their application range. Most produce a weld with low voltage and high current. The welder in this How-to operates from a secondary of 3vac. The primary is 120vac line voltage that should be treated with respect. The low voltage secondary makes the welder very safe, so the electrical shock hazard from the electrode is virtually non-existent. There is however the risk of burn due to the high temperatures as with any welder.

This particular welder is not intended to weld a body panel on your 1966 Jeep; it will not work well on material heavier than 20gauge sheet metal. The intended use is for small projects, for it is not capable of continuous operation. Possible uses are as follows: Welding electrode material for electrolysis cells. Working with the fine components of a vacuum tube. Building a light weight frame for a small robotic platform. Most of us have enough parts laying around to build a spot welder. If you have a microwave oven transformer (MOT) laying around, then you are half way there. On a related note, we had covered a microwave oven arc welder in 2006.

We also needed some heavy gauge copper wire. We used about four feet of 4AWG wire to build the spot welder in the photo. Other materials included scrap 2×6, 2×2, two copper screw type lugs, two copper welding cable lugs, two MIG welder tips, two 4″ x 3/4″ zinc plated corner braces, drywall screws, and three washers.

Pictured above is a working MOT. The first thing we had to do was remove the secondary coils. Namely the high voltage winding, and the low voltage winding. We used an angle grinder with cut off wheel while being careful not to cut the primary winding.

We cut the secondary flush with the MOT laminate core. Both sides of the MOT should be cut. Inspect the MOT for signs that the laminate has been welded. We have found that welded MOTs can handle a little more abuse than their sealed only counter parts. If possible try to keep the core insulation intact, where the secondary will be wound. Though it is not a show stopper if the insulation becomes damaged. The insulation makes it a little easier to wrap the heavy gauge secondary.

After removal of the secondary we had something that resembles the above photo. If the magnetic shunt material falls out be sure to replace it as it was before. The shunt keeps the core from transferring too much power to the secondary. A magnetic ballast if you will. The shunt acts to control the saturation of the core. A brute force project like this relies on such a shunt for proper operation.

Rewinding a MOT with 4AWG is no walk in the park. If you’ve damaged the core insulators, we suggest wrapping a layer of electrical tape in their place. This will help to avoid damaging the insulation on the wire as it is pulled through the core.  Our experience is that 3-4 windings is plenty. After all, this spot welder relies on high current and marginal resistance. Not high voltage.

We were careful to ensure that the secondary coil was wrapped in a helical manner to complete the secondary.

We mounted the MOT and 2×2 to the 2×6 base. This particular build used 12″ 2×6 with two 7″ 2×2. These dimensions may or may not work depending on the physical size of your MOT. The only critical part here is keeping the wire length as short as possible.

After the lower jaw was mounted, we also attached the corner braces. It was found that a spare piece of 2×2 as a shim worked well to align the upper and lower jaw. After the upper jaw was aligned we attached it to the corner braces with screws. This formed the hinged portion of the jaw.

The picture above shows the MIG welder tip and the screw type copper lug. This is an improvement from an earlier model we had built. Initially, we used copper tubing with a hole and a piece of 6AWG grounding wire serving as the welding electrode. The grounding wire was held in place by a screw that threaded inside the copper tube perpendicular to the electrode. It was very crude, but it worked. This new method is much more practical.

Here are the two electrodes ready to be fixed to the lower and upper jaws. We double checked the MIG electrodes to make sure they were tight. A loose connection will take heat away from the weld nugget.

Evenly aligning the welding electrodes, we were careful to keep the upper jaw in the natural position where it was mounted. This maintained a flat contact area for the welding electrodes. After we were sure that the electrodes had been properly aligned, the jaws were marked. We then drilled a small hole. Since we mounted with the grain of the 2×2 the holes helped to protect from splitting the 2×2.

With the electrodes mounted, we cut the wire to proper length. We never cut the exact amount we need. We always cut more than we need. This rule of thumb should apply to all electrical wiring. After all it is much easier to cut off excess than wrap a new secondary.

We bent the wires in to the approximate positions in which they were to be assembled and stripped the wire in preparation for the crimp type welding lugs. It is a good idea to strip more than is needed here as well. Simply cut off excess after sizing up the lugs depth. Never crimp insulation with the lug. This will create a potential problem area due to the loss of conduction.

Using a good non insulation crimp tool to secure the wire. We inspected the crimp and gave it the tug test. Simply tug on the wire if it is loose it will pull out. It if doesn’t pull out then an adequate crimp suitable for high current has been made.

The crimped wires were attached to the welding electrodes with screws. We were careful not to over tighten the screws. If a drywall screw had stripped out of the wood, we would have had to use a larger wood screw in its place. After both welding electrodes were fixed to the jaws, we aligned the electrodes. Using pliers we bent the electrodes so that they contacted each other evenly. The electrodes should be fairly close already since they were aligned before drilling.

We opened the jaws and wired the primary to an electrical cord and then tested the secondary. If the breaker trips, check for the following:

1. The secondary is  shorted (the jaws are closed)
2. The magnetic shunts are missing or not properly reinstalled
3. Faulty line wiring to primary or shorted primary
4. Too much load on the circuit of test or undersized breaker

We observed proper electrical wiring practices. It is also stressed that this is a welder and it should have a dedicated circuit as any other welder would have.

With the power physically disconnected we verified the welding electrode alignment with the material we intended to work on. Before connecting the power and performing an initial weld, we observed a few safety guidelines. This is a welder and will produce very high temperatures. Keep fingers away from the welding electrodes. Allow the material to cool prior to handling. Always wear eye protection. You may be interested in reading about spot welder parameters. There’s also the problem of combustible materials…

This Compaq used very thin aluminum to support the screen and connect the hinges. The metal broke and destroyed most of the lower plastic. We were able to make new supports from 22AWG stainless steel sheet metal. All the welds were made using the spot welder with a special power controller. The power controller will be covered in another how-to.

[Koil_1] knows he’s forgetful. In order to save himself from any undue harm, or possibly to keep from burning his house down, he felt he needed a timed power switch to run his soldering iron from. He realized he could harvest the relays and timer circuit from a microwave. This allows him to have presets for specific tasks. Considering the fact that you can get a used microwave for free or close to it most of the time, this was a great re use of something that might just go wasted otherwise. Great job [Koil_1].

[via Synaptic Seepage]