Want a two person self destruct button, but tired of pesky microcontrollers?

We all know that our precious cruisers/warships/assets can not fall into the wrong hands, and what better way to assure that information security than incorporating a self destruct button into the design? While the general premise is simple enough the only real way to make sure some crazy space-virus can’t infect your captain and force him to destroy your ship is to add a two button security system! Wait, what if it’s a computer virus?! Well [Andrea] has it covered with this two hand hand control switch. We guess you could also just use the scheme to flip on a dangerous piece of equipment, since it forces the operator to remove both hands from the machine to operate the buttons, but where is the drama in that?

The buttons are timed using a combination of voltage dividers and caps to activate transistors, one to activate the 555 timer and another to disable the button input after a half second or so. Since it’s all resistor capacitor timing your circuit may require just a bit of tuning (or precision components) to get everything right.  There is a bit of an issue with using two people to trigger the output, as the second button actually operates the output relay directly. If the second button is held it will only remain active until the timer’s output is triggered, but if your second in command gets cold feet and releases the button before the core goes thermo, well, you’ll have an embarrassing jog to the escape pods.

Check the video after the jump to see [Andrea] fiddling around with the switch.

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Quieting an inexpensive bench power supply

[Mike] just purchased this Atten APS3005S bench power supply for around $80. It does the job, but boy is it noisy! We were pretty surprised to hear it fire up in the video after the break. To make matters worse, the noise is persistent since the fan never shuts off. Having worked with other bench supplies he knew that a common feature included in many models is temperature controlled case fans. He set out to quiet the fan and implement a temperature switch.

For this project [Mike] had the benefit of looking at a nearly identical model that does have temperature switching. He discovered that the board on this one has a through-hole zero ohm resistor populated in place of a thermostat switch. That switch closes the connection at or above 45 degree Celsius, thereby turning on the cooling fan. Bridging the traces with a zero ohm resistor to save on production costs is what caused the fan to run continuously. After replacing the resistor with a KSD-01F and swapping out the stock fan for a high-quality version [Mike] has takes a noise maker and turned it into a device that’s kind to the ears.

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Hidden bookshelf switch

So you don’t have any secret passageways in your house, but if you’ve got a bookshelf this secret switch can add some fun to your routine. [Brandon] saw a commercially available version which was out of stock when he went to order so he set out to build his own.

He’s using the switch to operate a lamp. The donor part for the hack is a lamp dimmer which you’ll find at the big box store. This is really just a pass-through wall plug with an extension cord. By cutting the dimmer module off of the extension a push button can be used to connect and disconnect one of the conductors in the line. Make sure you use a push button rated or mains voltage!

To make the push switch work with a book [Brandon] bend a bracket which will slide into the spine of a hardcover. We love his homemade press brake (angle iron, a sturdy hinge, and a chunk of 2×4) used when shaping the bracket. Once everything’s in place nobody will ever know there’s anything special about those books.

Fix broken buttons on your ASUS computer monitors

One of the perks of writing for Hackaday is that we often find hacks that we’ve been meaning to do ourselves. Here’s one that will let us fix our borked ASUS computer monitor buttons. [Silviu] has the same monitor we do, an ASUS VW202, and had the same problem of stuck buttons. We already cracked ours open and realized that the buttons are not easily replaced (you’ve got to source the right one). We just unstuck the offender and vowed not to press that button again, but [Silviu] actually figured out how to disassemble and repair the PCB mount switches.

As with most consumer electronics these days the worst part of the process is getting the monitor’s case apart. The plastic bezel has little spring tabs all around it that must be gently pried apart. Once the PCB which hosts the buttons was removed, he took the metal housing off of the broken switch. Inside he found that a bit of metal particulate (leftovers from manufacturing?) were causing the problem. A quick cleaning with a cotton swab removed the debris and got the tactile switch working again.

Tiny audio switcher eliminates repetitive plug swapping


[Phil] uses both his computer’s speakers and a set of headphones while working at his desk, but he was growing tired of constantly having to remove the headset from his sound card in order to insert the speaker plug. He’s been meaning to rig something up to make it easier to switch outputs, but never seemed to get around to it until he recently saw this LAN-enabled audio switcher we featured.

His USB-controlled switch features a single audio input and two audio outputs, which he mounted on a nicely done homemade double-sided PCB. The switch can be toggled using any terminal program, sending commands to the on-board ATtiny13A via an FT232R USB to serial UART chip.

The switch’s operation is really quite simple, merely requiring [Phil] to type in the desired audio channel into the terminal. The ATiny and a small relay do the rest, directing the audio to the proper output.

Most useless machine upgrade — now with a button!

There’s a soft spot in our hearts for pointless projects, as long as they’re well executed. [Bertho] really hit the mark with his take on the most useless machine. We’ve seen several renditions of this concept, most of them hinging on a box that will turn a mechanical switch off whenever you turn it on. But this take uses a push button to activate a switch flipping mechanism on another part of the machine.

You can see the drive gears in the image above. The final gear has a small bar which flips a switch to one side or the other. The circuit does this without the need of a microcontroller. A 7400 series NAND gate chip, some passive components, and two mechanical relays are all it takes. At each push of the button, the logic chip trips one of the relays to trigger the appropriate motor direction based on the current state of that switch. You can press the button during movement, but all that will do is delay the inevitable flip of the switch.

IP-based engine remote enable switch


[Mariano] owns a late 90’s Jeep Wrangler, and had no idea just how easy it was to steal. Unfortunately for him, the guy who made off with his Jeep was well aware of the car’s vulnerabilities. The problem lies in the ignition – it can be broken out with a screwdriver, after which, the car can be started with a single finger. How’s that for security?

[Mariano] decided that he would take matters into his own hands and add a remote-controlled switch to his car in order to encourage the next would-be thief to move on to an easier target. He describes his creation as a “remote kill” switch, though it’s more of a “remote enable” switch, enabling the engine when he wants to start the car rather than killing it on command.

The switch system is made up of two pieces – a server inside the car’s engine bay, and a remote key fob. The server and the fob speak to one another using IPv6 over 802.15.4 (the same standard used by ZigBee modules). Once the server receives a GET request from the key fob, it authenticates the user with a 128-bit AES challenge/response session, allowing the car to be started.

It is not the simplest way of adding a remote-kill switch to a car, but we like it. Unless the next potential car thief digs under the hood for a while, we’re pretty sure [Mariano’s] car will be safe for quite some time.