Star Trek Style Pneumatic Doors That Don’t Require A Stagehand

November 27, 2011 by Brian Benchoff 63 Comments

In 1966, [Gene Roddenberry] introduced fully manual doors powered by a stagehand on Star Trek. The fwoosh sound of the door was later dubbed into each show, but progress marches on, and now [Alex] created his own Star Trek-style automatic doors for his house.

The build includes a ‘control panel’, and [Alex]’s door operates in three modes: Open, and stay open; Close, and stay closed; and Automatic. The control panel itself is fairly remarkable. A small puck interacts with a magnetometer underneath [Alex]’s counter. If the puck is pointed towards ‘Open’, the door stays open. If the door is pointed towards ‘Closed’, the door stays closed. If the puck isn’t near the magnetometer, the door operates in automatic mode with the help of a few IR sensors to detect someone trying to get in or out of [Alex]’s kitchen.

For the mechanical portion of the build, [Alex] used a One meter long piston with the quietest air compressor he could find. We can’t tell from the video after the break if the compressor ever kicks in, but [Alex] says it’s about the same volume as his fridge. As a small added bonus, the new automatic door does have a fwoosh sound, just like [Gene] would have wanted.

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Two Ways To Convert An Electric Cooler To A Humidor

November 27, 2011 by Mike Szczys 6 Comments

It’s not a proper humidor in the technical sense (there isn’t any specific way to moderate the humidity) but [Dzzie] came up with a couple of ways to keep his cigars cool in the summer heat.

Both versions use a Coleman electric cooler as the enclosure. This hardware uses a Peltier device to keep it cool inside. The first attempt at use a thermostat with this worked by adding an external relay to switch mains power. A thermostat dial hangs out inside the cooler to give feedback to the relay board. This worked, but it’s a really roundabout approach since the cooler operates on 12V, and this method uses a mains-to-12V adapter. If [Dzzie] decides to hit the road the relay won’t work when the cooler is powered from a 12V cigarette lighter in the car.

The second rendition fixes that issue. He moved to a 12V relay, and used a car cellphone charger to supply the 5V of regulated power his control circuitry needs to operate.

Pushing Chest Strap Heart Rate To A Stock Exerciser Display

November 26, 2011 by Mike Szczys 3 Comments

This hack came out so well that [Levent] wishes he had tried it years ago. When exercising he wears a Polar heart rate monitor which sends data from a chest strap to his wristwatch. But his exercise bike also has a heart rate readout that depends on your hands touching metal contacts on the handlebars. He set out to see if he could patch the chest strap data into the exercise bike LCD display.

The first part of the hack is really simple. As we’ve seen several times before, you can buy a receiver module which grabs data from the chest strap. Now it was a matter of patching the data from this receiver into the Schwinn 213 recumbent exercise bike. [Levent] pulled out the PCB and located the small daughterboard that is responsible for the hand grip heart rate. With careful study he was able to identify the pinout. There are two data lines. One is responsible for the heart rate detected signal, the other pushes the actual heart rate data. On a hunch he hooked a signal generator up to the latter and discovered that all it takes is a square wave.

The rest is pretty straight forward. Check out the proof in his video after the break. Continue reading “Pushing Chest Strap Heart Rate To A Stock Exerciser Display” →

A Doorbell Pleasing To Both The Ears And Eyes

November 22, 2011 by Mike Nathan 15 Comments

campanello-doorbell

When [David] moved into his new house, one of the things he noticed was that his doorbell was pretty lame. Coming from a home equipped with a solenoid and chime bell, his new wireless solid state doorbell sounded terrible to him.

Crummy sound aside, the doorbell hardly ever worked properly, but alas, other projects cropped up and years went by before [David] addressed his doorbell problem. Like many things that take a long time to come to fruition, we think his resonator bell based solution was well worth the wait.

One of his main goals was to make a nice sounding doorbell that also looked great. He mounted a kid’s resonator bell toy on a sheet of wood, creating his own wooden mallets for the job. He initially had a tough time locating actuators for his doorbell, but found a solution in geared pager motors as featured in another xylophone hack on Make. With the hardware taken care of he focused on the electronics, which consist of a pair of Arduino clones – one on the display and one in his basement.

Stick around to see [David’s] Campanello doorbell in action, and be sure to check out his site for more details if this sounds like something you would like to have in your home.

[via Make]

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Power Strip Hack Reduces Standby Electricity Consumption

November 21, 2011 by Mike Nathan 31 Comments

computer-standby-circuit

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!

Python Powered Sprinkler System Wastes No Water

November 19, 2011 by Mike Nathan 31 Comments

rain-gauge

One thing that annoyed [Jashua] to no end was hearing his automated sprinkler system kick on in the middle of the night, when it had rained earlier in the day. He wished that his sprinklers were a bit smarter, so he decided to give the system an upgrade.

Rather than pay hundreds of dollars for a more sophisticated automation system, he spent about $45 on supplies and scrounged together some items he had sitting around the house to make a rain-sensing module of his own.

The resulting project, Pysprinklers, uses Python along with a handful of components to better manage his water usage. He got his hands on a cheap rain gauge, and modified it with a game controller and a set of magnetic surface contacts. If there has been a significant amount of rain in the last 24 hours, his system will prevent the sprinklers from turning on. Additionally, if there is rain in the forecast, the sprinklers will be delayed a bit to see if rain makes its way into the area.

We’re all for saving money (and water), so we think [Jashua’s] system looks great, especially because he ended up using a handful of things he already had on hand.

Whole House Battery Backup Used For Lower Power Bills

November 17, 2011 by Mike Szczys 78 Comments

[Photonicinduction] has an impressive battery backup installation that powers his whole house. Unlike a standalone emergency generator which would require you to hook up all of the device you want to run, this setup sits in between the power meter and the breaker box, ready to step in when needed.

But get this, he’s not just using it as a backup system. It kicks in during the day to run everything including two freezers, a refrigerator, his lights, television, and computers. That’s because the price per kilowatt-hour is quite a bit higher during the day than at night. So after 10:30pm the system patches his house back into the grid and charges the batteries for use the next day.

What you see here is just a portion of his system. The control board is not pictured but is very impressive, including a network of relays which are used as a fail-safe system so that there are no conflicts between mains and the battery system. Check out his 15-minute walk through of the system after the break. Continue reading “Whole House Battery Backup Used For Lower Power Bills” →