Here’s a cool little variation of that handy little function called Wake on LAN — [Jonathan] found himself locked out of his apartment one too many times, so he decided to add his own fail safe backup in order to get inside without a key — using a Raspberry Pi of course.
His apartment is one of those older style ones where the door is always locked and you use a buzzer to let someone in (or a key to get in yourself). This made it super easy to add some internet connectivity to the system. [Jonathan] tapped into the buzzer with a relay since the system uses medium voltage AC to operate. A Raspberry Pi triggers a transistor using its GPIO to click the relay on and off, effectively controlling the lock.
Using a WiFi dongle he’s connected the Pi to his home network and written a simple perl script to trigger the relay — all he has to do is visit a URL on his phone or computer and the door will unlock instantly!
Once the system worked [Jonathan] soldered all the components onto a breadboard and hooked it up. He still needs an enclosure for it, but it’s been working well since he installed it.
Another option would be to use an RFID tag system through the door, which could be pretty cool as well.
At home, [Daniel] has an extremely powerful dual quad-core Xeon system with ECC RAM that he uses for heavy lifting tasks – compiling, CUDA processing, and actual computing. Of course the electric bill for running this box all the time would be crazy, so Wake on LAN it is. There’s only one problem: for some reason, the BIOS doesn’t have Wake on LAN. The solution, of course, was a microcontroller system that would listen for the magic WoL packet and turn the computer on when it was received. This project eventually turned into a great case mod with an integrated LCD that powers the computer up over Ethernet, shows the current running processes, CPU and memory usage, and is an excellent use of a TI dev board.
The dev board in question is a TI Sitara AM355x starter kit that runs Linux, has two Ethernet ports and a touch sensitive LCD, and more than enough power to handle something as simple as a system monitor. To power on his monster computer from the dev board, [Daniel] is using a LED on the board, an inverter, a ULN2003 driver chip, and a relay connected to the computer’s power button. It’s not exactly a masterpiece of craftsmanship, but the dev board looks good mounted in the case, and from the videos below, it’s a great way to get system information embedded right into a computer case.
Continue reading “Wake On LAN With A Dev Board”
For years, [Rasmus] has left his computer connected directly to the mains power so that he can turn it on via Wake on Lan. While powered down, it would still continuously consume about 6W of electricity, but now that he didn’t need it to be on standby so often, he wanted to make it more energy efficient.
In Denmark, where he lives, many people use power strips that have an onboard USB cable. These strips are meant to reduce the standby power consumption of PC peripherals such as monitors by powering on the mains sockets only when the computer is active. He decided the easiest way to cut his standby energy consumption to 0W would be to power his computer via this strip as well.
While it sounds great in theory, it presented a sort of chicken/egg problem. If the computer needs to be turned on for the power strip to recognize it, then how could he also supply power to the computer from the same strip? His solution was a small circuit that would charge up while the computer was running, and still hold enough juice to kickstart the PC’s boot process, thus turning on the power strip.
It really is an ingenious way to go about things, nice job!
[Jachin] sent in his network port tester built from a network card, wake on lan cable and a battery holder. Three AAs supply 4.5v DC just like the motherboard would to the card via the WOL cable. Nice trick, I’d consider adding a static bag at the least to keep the card from getting zapped.