Home Automation Hack Controls Lights Based On Head Count

September 19, 2012 by Mike Szczys 19 Comments

This home automation hardware turns on and off the lights based on room occupancy. The hack is an extension of an earlier version that was only a proof of concept. [RPisces] took the idea and made it into reality by mounting the sensor hardware in a doorway.

He prototyped the device using the MSP430 launchpad. It monitors a pair of IR distance sensors which record a change when something passes between them and the opposite side of the hallway. This is a good sensor choice as it only requires hardware on one side of the passageway. Because two of them are used, it’s quite simple to figure out if a person is entering or leaving the room based on which is tripped first.

In this case [RPisces] drives a relay to switch a lamp on and off. But it could be used for just about anything. We’d enjoy seeing it trigger an audio system like the one [Quinn’s] installing in every room.

Art Controller: Relay Board With Switches For Timing

September 13, 2012 by Mike Szczys 12 Comments

Meet the Art Controller, a new dev board available over at Evil Mad Scientist Laboratories. It provides a drop-in solution for switching higher voltage loads (but not mains). The thing we like most about it is the ability to alter a switching delay without reprogramming the firmware.

The board uses an ATtiny2313 for control. It’s fed regulated 5V power from the on-board 7805 linear regulator. The relay can handle a 24V DC or 40V AC load, which is targeted at an audience that needs electronic switching for art-related devices but doesn’t want the hassle of designing a circuit every time. This offers a single shot, or repeat action, with that bank of DIP switches selecting a delay from once every second, to every 31 hours. It can get its initial trigger from anything that can pull a pin low, like a button, or a coin acceptor.

Keep this in mind. The open source nature of the project means it could come in handy as a reference design.

Word Clock Of A Different Nature

August 30, 2012 by Mike Szczys 8 Comments

This work clock functions in an unexpected way. With each passing second it displays a random four letter word on the right side of the display. Traditional word clocks tell the time in natural language, but this one is simply used as a learning opportunity.

[Iron Jungle] got his hands on the display for just five buck from Deal Extreme. Looks like the price has gone up two dollars but that’s still a bargain. He wanted to use all eight digits of the display, and was looking for an opportunity to control more than one i2c device at a time. He ended up rolling an EEPROM and DS1307 RTC into the design. He figured the could display 24-hour time on four of the digits, and pull a library of four-letter words off of the EEPROM to fill the rest. He grabbed a word list off of the Internet then used a Python script to remove words containing 7-segment unfriendly characters (K, M, V, W, X, Z). The final touch was to use a salvaged relay to give the clock a ticking sound. Hear it for yourself in the clip after the break.

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Bluetooth Control In A Power Strip

August 28, 2012 by Mike Szczys 16 Comments

[Mansour] had a ceramic space heater mounted near the ceiling of his room. Since heat rises this is not the best design. He upgraded to an infrared heater which works a lot better, but lacks the timer function he used on the old unit. His solution wasn’t just to add a timer. He ended up building a Bluetooth module into a power strip in order to control the device wirelessly. He ends up losing all but two outlets on the strip, but everything fits inside the original case so we think it’s a reasonable trade-off.

He uses relays on both the live and neutral wires to switch the two outlets. These are driven via MOSFETs to protect the ATmega168 which controls the board. The microcontroller and Bluetooth module both need a regulated DC power source, so he included a transformer and regulator in the mix. After the break you can see him demonstrating the system using two lamps. There’s even a terminal interface which lets you select different control commands by sending the appropriate character. This interface makes script a breeze.

At least this power strip doesn’t spy on you.

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Mechanical Relay Logic That Was Snubbed For A Microcontroller

July 30, 2012 by Mike Szczys 27 Comments

[Alex] was tasked with a control design problem for a set of motors. The application called for the back of a truck to open up, some 3D scanning equipment to rise from its enclosure, and finally the equipment needed to rotate into place. All of this needed to happen with one flip of a switch, then proceed in reverse when the switch was turned off. We can understand why the final design used a microcontroller, but we also think that [Alex’s] relay logic circuit is an eloquent way of doing things.

He uses limiting switches as the feedback loop for the logic. In the video after the break he walks us through the schematic. Each of the three motors has an up and down limiting switch. These control the three relays which switch power to the motors. We like the design because interrupting the movement mid-operation provides no problem for the system. The only real issue we see is that relays wear out, and the automotive application of the hardware may cause this to happen more quickly than normal.

You may recognize the clear gears used in the demo. [Alex] previously showed us how he makes those.

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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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Christmas Prep Starts Early: MIDI Control For Strings Of Lights

July 3, 2012 by Mike Szczys No comments

If you’re planning to outdo yourself with this year’s Christmas decorations now’s the time to start planning. After all, what else have you got going on since the dreadful heat is making outdoor activities a sweat-soaked misery? Take some inspiration from [Tim] who just finished prototyping a wireless MIDI controller for his strings of Christmas lights. You can just see the four spools in the distance which are lighting up as he tickles the ivories.

The wireless link is provided by a WiFi access point which uses its USB port to control the external hardware. This is a USB Bit Whacker board which in turn drives a relay board that was designed to switch mains voltages. The high voltage parts of the rig are housed in a plastic food storage container which hosts two pair of outlets to drive four channels in total. [Tim] is happy with the outcome, which he shows off in the video after the break, and hopes to expand to a total of sixteen channels for this year’s festivities.

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