USB Killswitch Turns Off Your Home Entertainment Bling Automatically

October 12, 2011 by Mike Szczys 16 Comments

Finally, the USB port on the back of your television can be tapped for something useful. [Don] is using this add-on device to automatically cut the power to his Ambilight clone. Initially, he got tired of unplugging the power adapter each time he shut off the television, so he added a switch. But laziness overcame him and he decided he needed an automatic method. After probing around on the connections available, he established that the serial interface (normally used for servicing the device) was not of any use, but the USB port is. He measured the voltage of the power bus to be 5V when the TV is on, and 0.15V when it is off. He whipped up the circuit you see above which uses the USB connection to trigger a relay, connecting power to his Ambilight clone when the television comes on, and disconnecting it when the set is switched off.

Our dream has always been an XBMC capable device that can Velcro to the back of a TV, and be powered from that USB port. Unfortunately the Beagle Board hasn’t yet made it to a stable level when running XBMC. Our next hope is the AppleTV 2, which can run XBMC but would require some hacking to get it working off of the USB port, raising concerns about how much current it would draw at 5V.

Light Up Your Workshop With This Arcade Button Light Switch

September 7, 2011 by Mike Nathan 27 Comments

[Pete Mills] was browsing around online when he came across an arcade button light switch and immediately wanted one. He didn’t however want to pay the $35 asking price for the switch, so he decided to build it himself.

He says that his solitary arcade machine doesn’t warrant its own room, so he figured he would wire the switch up to an extension cord in his workshop instead. The switch was made with parts he had on hand, so seeing as he didn’t have any triacs, he opted to use a relay in its place. He thought about how he would construct a simple flip flop circuit for the switch, and settled on using a simple 555-based circuit instead of a pair of transistors.

The end result looks every bit as nice as the version available for sale online, and it works great as you can see in the video below. [Pete] has circuit schematics available on his site should you want to build your own, so if you do, let us know in the comments – we’d love to see different variations on the circuit design.

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High Voltage: Using Enclosed Relays For HV Switching

August 19, 2011 by Mike Szczys 21 Comments

After seeing many projects that use microcontrollers to switch mains voltages [Rob Miles] decided to share his preferred method. The shots you see above are an enclosed relay, part number RIBTU1C manufactured by Functional Devices Inc.

This in itself is not the full control scheme that he uses, but it takes care of the bulk of the hardware. He uses a triggering circuit based on a 555 timer (PDF). [Rob] mentioned that if you shop around, you can get the relay, 555 timer, and other components for under $15. This is a great solution for the money when you consider that you get an enclosure meant for handling high voltage and a nice terminal block to which you can connect the mains wiring. The relay itself can be triggered by a 9V battery via the transistor in the control circuit.

Notice the protoboard in the image above. There’s plenty of room for your driver circuit to rest inside the box, protected by that barrier from the HV circuitry. Check out the rest of the images he sent us after the break.

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Most Useless Machine Upgrade — Now With A Button!

August 7, 2011 by Mike Szczys 11 Comments

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.

Washing Machine Mechanical Timer Replaced With Microcontroller

June 5, 2011 by Mike Szczys 12 Comments

After the electromechanical timer on [Paul Canello’s] washing machine broke for the third time he decided he needed to stop repairing it and find a more permanent fix. He decided to build his own microcontroller-based system for washing his clothes (translated). Caution: The image links on [Paul’s] page seem to be broken and will unleash a never-ending storm of empty pop-up windows if you click on them. We’ve embedded all of the images after the break to save you some hassle.

The controller on a washing machine is nothing more than a mechanical alarm clock. It starts the cycle, then moves through various modes based on the passage of time. [Paul] started his hack by observing how long the delay between cycles was meant to be, and recording which parts of the machine were switched on and off at each stage.

It turns out that when the mechanical knob is turned, it reroutes how water flows through the detergent chamber. Since that knob won’t be in the new system [Paul] came up with a way for the microcontroller to handle this by using a servo motor. The rest of the control involves relays to control the motor, and solenoid valves for the water. There are also pressure switches that give feedback for the level of the water in the machine. A PIC 16F872 serves as the new controller, with the help of a 7 segment display, a buzzer, and a pair of buttons as the user interface.

This is an older project, but after reading about the Arduino controlled dishwasher [Ramiro] sent us a link. Thanks! Continue reading “Washing Machine Mechanical Timer Replaced With Microcontroller” →

Relay Calculator

April 22, 2011 by Kevin Dady 6 Comments

Calculators are a handy tool to have around in just about every application. We often take them for granted today, but even when I was a kid they were still sort of expensive devices that you put thought into buying. Illustrating just how far we have come is this awesome Relay Calculator brought to us by [Team 619].

Featuring an optical slider input system, the user can select any two 4 bit numbers and can add or subtract them. Logic is carried out by a couple handfuls of relays setup to be AND, OR, or XOR gates, which are then linked together to build adders.

Output is in binary as well, in the form of lights, though we cant really tell if those are some form of tubes or if they are just rods lit on end. Either way if you require a lot of nibble math and want a conversation starter this suits the bill quite niceley. Otherwise you can keep hooking up more and more relays and maybe one day make your own relay computer.

Join us after the break for a quick video!

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Reversible Relay-based Motor Controller

April 14, 2011 by Mike Szczys 16 Comments

[Nothinglabs] built this motor controller as an alternative to using an H-bridge. They call it the RAT controller which stands for “Relay and Transistors”. You can see above that two Darlington transistors along with their base transistors allow logic signals to switch the relay on and off, driving the motor in one direction or the other based on the open or closed state of the relay. See it working in the video after the break.

It’s a nice little workaround with few parts, but because the relay is mechanical there will be a short lifespan when compared to solid-state motor controllers. That’s okay, because the motivation here was lack of parts on hand, rather than an increase in performance. It’s also worth mentioning that all of these parts can be purchased at your local Radio Shack when you don’t want to wait for component orders by mail. We certainly appreciate that it takes far few components than [David Cook’s] H-bridges. His designs are our favorite – we’ve used them in our own projects – but for quick and dirty you can’t beat five components and the short assembly time needed when using this type of dead-bug style soldering.

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