Father/son Team Goes Big With Backyard Observatory

July 19, 2012 by Mike Szczys 40 Comments

Oh that? It’s just the backyard observatory we built last summer. You know, for fun. This is a conversation we image [Kakon24] and his dad are having quite often these days. They’re astronomy interests just got a big equipment upgrade when they built a huge observatory on their homestead. Now we don’t proclaim to know a lot about observatory quality, but this is head and shoulders above what most people manage to acquire.

It isn’t a simple build either. It’s a full-fledged building of its own, starting with a poured foundation, then stick framing which was covered in stone work. The images tell the story of the build, but for information on the hardware you’ll want to read through the comments over on the Reddit Astronomy thread. Sounds like the scope itself cost over 100 grand so having a proper building to protect it is a must.

Monitoring Your Home Energy Use

July 18, 2012 by Mike Szczys 19 Comments

[Dave’s] been elbow-deep in mains voltage while building this home energy monitoring rig. He started with an approach that is different from most we’ve seen before. He wanted a system that could make a linear measurement to keep the accuracy as high as possible. His first thought was to use a opto-isolated linear amplifier to measure voltage, but ended up altering that plan since he’s looking for digital values when all is said and done.

He’s using an ADC on the mains side of the interface board, then sending the digital values to an Arduino with opto-isolators to keep the high voltage separate from the low. This does complicate things a little bit, as he has low voltage rails on either side; 0V and 5V to run the ADC on the mains side, and separate 0V and 5V to run the Arduino. To solve the problem of accurate current measurement over the full range a house uses he opted for a Programmable Gain Amplifier. It’s addressed via SPI and allows him to adjust resolution to facilitate accurate measurement of very small currents. We think anyone who has tried to measure small appliances (like an alarm clock) with a Kill-A-Watt and gets a zero reading will appreciate this.

The Arduino sends data via a serial connection, which [Dave] is currently graphing using his laptop. It would be nice to see a simple web-server using the Ethernet shield (or a different board like the RPi) so you could log in from the couch and see what’s been going on with your home grid.

Garage Door Opener Now A Bedroom Door Closer

July 13, 2012 by Mike Szczys 12 Comments

[Roy] had an extra garage door opener on hand and decided to put it to use as a remote control closing mechanism for his bedroom door. We gather he has some noisy housemates as the inspiration for the project came from not wanting to get out of bed to close the door when the ruckus interrupts his TV watching.

The image above shows the hinged system which translates the linear motion from the garage opener track to the rotational force necessary to swing the door closed. We’d say he really nailed it because the system matches the angle of the door jamb perfectly, and when the door is fully open the angle bracket is almost flat against the wall. We certainly don’t have the same need for closing doors, but the mechanism is something to keep in mind.

The motor for the opener is hidden beneath his desk. You won’t be able to see it in the video after the break because he built a matching enclosure around it. Now he just needs to add some WiFi connectivity and he can ditch the uni-tasking RF remote for a smart phone app.

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Cat Trainer Will Keep Them Off The Counters

July 12, 2012 by Mike Szczys 18 Comments

Our cats are not allowed on the kitchen counters, and [Iron Jungle] has the same rule. But he spotted some foot prints on the hood above his range and the addition of a security camera caught this picture of [Kelso] breaking the rules. Since he’s not always around to make the fur-ball behave he built an electronic cat trainer to do it for him.

The functionality needed isn’t very intricate. You need to monitor when the cat is where it shouldn’t be and then chase it away. For the latter he grabbed an infrared range finder. When the cat passes in front of the sensor it will trigger the second part of the system: a high-pitched buzzer that’s extremely loud. Any microcontroller will have no trouble driving the system. In this case it’s a PICAXE 28X1.

You can see the trainer in action after the break. It definitely works, because just playing the video chased our own sleeping kitty out of the room.

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Monitoring A Clothes Washer With An Accelerometer

July 7, 2012 by Mike Szczys 15 Comments

[Viktor’s] washing machine did a good job of cleaning his clothes, but it kept a bit too quiet about it. The machine doesn’t have an audible alert to let him know the cycle has finished. He decided to build his own alarm which can just be slapped on the side of the machine.

You can see that a couple of magnets hold the board to the metal housing of the washer. The board doesn’t actually connect to any of the machine’s circuitry so this should work about equally as well for any unit. The detection is based on motion, thanks to a Freescale MMA7361 3-axis accelerometer. When he starts a load of wash he flips the power switch for the board on. The PIC 12F683 that drives the device starts monitoring the accelerometer for changes. If it goes for more than about one minute without reading motion the piezo buzzer starts beeping. It’s a fun and easy solution along the same line of this oven pre-heat alarm add-on.

TI Chronos Watch Monitor Your Sleeping Infant

July 4, 2012 by Mike Szczys 21 Comments

[Bill] wants a little piece of mind when his infant is sleeping in the other room. For him, the audio-only baby monitor could use some improvement. His proof-of-concept is that blue patch Velcroed on the swaddled infant. It monitors movement, orientation, and temperature and alerts you when something’s amiss.

Inside the pouch you’ll find a TI Chronos eZ430 wristwatch with the band removed. It’s a nice hardware choice because it includes an accelerometer, temperature sensor, and RF link to a USB dongle. [Bill’s] code sends a data packet to the PC about once a second. The PC watches to make sure there’s slight motion, indicating the baby is breathing. This part doesn’t work all that well as the accelerometer doesn’t pick up tiny movements all too well, but it does have potential. In the video after the break you can see the functions which make sure the baby doesn’t roll onto its belly, and that she’s not too cold do work extremely well.

We wonder if the accelerometer would pick up more motion if the watch was hung from a string inside of a small enclosure. This way it would swing back and forth with small movements. But perhaps that would make the whole thing too bulky?

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[RobB’s] House Has No Light Switches

July 4, 2012 by Mike Szczys 46 Comments

So [RobB] wanted to take out all the light switches in his house. His plan was to replace them with a system that could be operated from his smart phone. But his wife insisted that there still must be some way to control the lighting directly — we have to agree with her on that one. The solution was to develop a system that switches the lights via a touch sensor or by Bluetooth.

The touch part of the project is pretty easy. He coated the back of a blank outlet plate with tin foil and hooked it to a microcontroller with a couple of resistors. He’s using an ATtiny85, which can be programmed using Arduino sketches, so the software side is made easy by the CapSense Library. The chip also uses the software serial library to communicate with a Bluetooth module. You can see the result of both in the demo video after the break.

Of course you need to throw a relay in there to switch mains, and find a way to power the uC and Bluetooth module. [RobB] went with a tiny plug-in USB power converter and managed to fit everything in a single-gang switch.

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