[Paulo’s] garden lights are probably a bit more accurately automated than anyone else’s on the block, because they use latitude and longitude clock to decide when to flip the switch. Most commercial options (and hobbiest creations) rely on mechanical on/off timers that click on an off every day at the same time, or they use a photosensitive element to decide it’s dark enough. Neither is very accurate. One misplaced leaf obscuring your light-dependent resistor can turn things on unnecessarily, and considering the actual time of sunset fluctuates over the year, mechanical switches require constant adjustment.
[Paulo’s] solution addresses all of these problems by instead relying on an algorithm to calculate both sunrise and sunset times, explained here, combined with swiftek’s Timelord library for the Arduino. The build features 4 7-segment displays that cycle through indicating the current time, time of sunset and of sunrise. Inside is a RTC (real time clock) with battery backup for timekeeping along with an Omron 5V relay to drive the garden lamps themselves. This particular relay comes with a switch that can force the lights on, just in case.
Check out [Paulo’s] project blog for the full write-up, links to code and more details, then take a look at some other home automation projects, like the SMS-based heater controller or occupancy-controlled room lighting.
[SilverJimmy] already had a full-sized 50 watt laser cutter, but he decided to try his hand at putting together something smaller and microcontroller-driven. The result is this adorable little engraver: the MicroSlice.
To keep the design simple, [SilverJimmy] opted for a fixed cutting table, which meant moving the cutting head and the X-Axis as a unit along the Y-Axis. The solution was to take inspiration from gantry cranes. He snagged a couple of stepper motors with threaded shafts, designed the parts in Inkscape, then fired up his full-size cutter to carve out the pieces. An Arduino Uno and the relays for the laser and fans sit on the MicroSlice’s bottom platform, and two EasyDriver motor controllers sit above them on the next layer.
Swing by the Instructables for more details including the source code, and to see a video of the engraver below. [SilverJimmy] sourced his laser from eBay, but check out the engraver from earlier this year that used a DVD diode.
Continue reading “Microslice: The Tiny Arduino Laser Cutter”
The Hackaday tips line is always full of the coolest completed projects, but only rarely do we see people reaching out for help on their latest build. We’ll help when we can, but [Tim]’s relay-based CPU has us stumped.
[Tim] already has the design of his relay CPU completed with a 12-bit program counter, sequencer, ALU, and a transistor-based ROM. The problem he’s having deals with the mechanics and layout of his homebuilt CPU. Right now, all the relays (PC pin, we guess) are glued top-down to a piece of cardboard. This allows him to easily solder the wires up and change out the inevitable mistakes. This comes with a drawback, though: he’s dealing with a lot of ‘cable salad’ and it’s not exactly the prettiest project ever.
The ideal solution, [Tim] says, would be a PCB with through-hole plating, but this isn’t easy or cheap for the home fab lab. We’d suggest some sort of wire wrap setup, but proper wire wrap sockets and protoboards are for some reason unreasonably expensive.
If you have an idea on how to do the mechanical layout and connections of a relay-based computer, drop a note in the comments. [Tim] has a very cool project here, and it would be a shame if he were to give up on it due to a lack of tools.
Video below, and if you’re having a problem with a project, feel free to send it in.
Continue reading “How Do You Build a Relay CPU?”
[David Burroughs] wrote in to share this dial telephone museum exhibit he built and we’re glad he did because we love interactive museum hacks. He mentions that it’s not really tied to the theme of the Roads and Rails Museum in which it’s installed. But when we think of railroad history we also think of telegraph. And that’s just a hop, skip, and a jump from telephones.
The display allows museum goers to play with the rotary dial on the phone. The box next two it contains a 10-position relay increment switch. So each pulse from the dial increments the switch. There’s a satisfying click, a moving arm, and different colored LEDs which highlight the inner workings. An Arduino board monitors the phone, displaying the dialed number on a seven segment display then incrementing the relay.
We figure the interesting part is to see that telephony used to use mechanical switching like this. But the video below includes a story about the kid who asked how you carried this phone around. This brings to mind the phrase “hang up the phone”, which doesn’t have the same literal meaning it used to.
Continue reading “Rotary phone museum exhibit”
The black box mounted between two garage doors is actually a water heater controller. The entire assembly is a conglomeration of hacks which [Simon] added to his garage over the last four years. We’ll give you a quick rundown, but the entire story is told in his blog post.
Back when the house was built [Simon] was approached by the contractor who offered to throw in remote control for the garage door rollers for just 1500 Australian Dollars (about $1350 with today’s rates). That sounded quite steep to him. He managed to add his own remote control for about a third of the price. But there were a few missing features. Notably, a lack of a light that comes on when the doors open. He also didn’t like that the button inside the garage was on the motor, which is mounted quite high.
Years later his water heater controller needed a firmware upgrade from the manufacturer. Check this out: they replaced the entire controller rather than flashing the PIC 18F2321 inside. What a waste! But in this case [Simon] snagged the old unit, which included several mains rated relays. He connected one up to a light socket seen above, and outfitted several illuminated buttons on its original enclosure. Now he has the satisfaction of a light that comes on with when the door opens, and shuts itself off after a preset delay.
Now his daughter wants smartphone control. But that’s as easy as hacking a Bluetooth headset.
The round-about way this iPhone garage door opener was put together borders on Rube Goldberg. But it does indeed get the job done so who are we to judge? Plus you have to consider that the Apple products aren’t quite as hacker friendly as, say, Android phones — so this may have been the easiest non-Jailbreak way.
The main components that went into it are the iPhone, a Wemo WiFi outlet, and a 110V rated mechanical relay. But wait, surely it can’t be that simple? You’re correct, just for added subterfuge [Tall-drinks] rolled IFTTT into the mix.
You may remember hearing about If This Then That from the Alert Tube project. It’s a web-based natural language scripting service. Throw everything together and it works like this: The iPhone sends a text message which IFTTT converts to a Wemo command. A power cord connects the Wemo outlet to the 110V electrodes on the relay. The normally open connection of the relay is attached to the same screw terminals of the garage door opener as the push button that operates it. When the relay closes, the garage door goes up or down.
The biggest problem we have with this is the inability to know if your garage door is open or closed.
One aspect of the Raspberry Pi that has always challenged us is the power supply. It was a great idea to power the board from a standard micro-USB port because economy of scale makes phone chargers (even in the 1A range necessary for stable operation of the RPi) cheap and easy to acquire. The thing we miss is the ability to power the device on and off using the built-in hardware. The quandary has given rise to many different solutions, and the ATX Raspbi smart PSU is one of the better ones we’ve come across. It’s a nicely packaged take on the PIC-based version we saw earlier in the year.
The device is a small PCB that acts bridge between the micro-USB power supply and the RPi board. It offers several breakout headers, one of which is used for a power button. The button is monitored by a microcontroller that switches the on-board relay accordingly. But it won’t just kill the power when you want to shut down. It first signals one of the RPi GPIO pins, causing the OS to execute a shutdown script. It then monitors the RPi for the shutdown tasks to finish before cutting the power.
Continue reading “ATX Raspi is a smart power source for Raspberry Pi”