Graphing the efficiencies of LED light strips

After adding a few LED light strips above his desk, [Bogdan] was impressed with the results. They’re bright, look awesome, and exude a hacker aesthetic. Wanting to expand his LED strip installation, [Bogdan] decided to see if these inexpensive LED strips were actually less expensive in the long run than regular incandescent bulbs. The results were surprising, and we’ve got to give [Bogdan] a hand for his testing methodology.

[Bogdan]’s test rig consists of a 15 cm piece of the LED strip left over from his previous installation. A Taos TSL2550 ambient light sensor is installed in a light-proof box along with the LED strip, and an AVR microcontroller writes the light level from the sensor and an ADC count (to get the current draw) of the rig every 6 hours.

After 700 hours, [Bogdan]’s testing rig shows some surprising results. The light level has decreased about 12%, meaning the efficiency of his LED strip is decreasing. As for projecting when his LEDs will reach the end of their useful life, [Bogdan] predicts after 2200 hours (about 3 months), the LED strip will have dropped to 70% of their original brightness.

Comparing his LED strip against traditional incandescent bulbs – including the price paid for the LED strip, the cost of powering both the bulb and the strip, the cost of the power supply, and the time involved in changing out a LED strip, [Bogdan] calculates it will take 2800 hours before cheap LEDs are a cost-effective replacement for bulbs. With a useful life 600 hours less than that, [Bogdan] figures replacing your workshop lighting with LED strips – inexpensive though they are – isn’t an efficient way to spend money.

Of course with any study in the efficiency of new technology there are bound to be some conflating factors. We’re thinking [Bogdan] did a pretty good job at gauging the efficiency of LED strips here, but we would like to see some data from some more expensive and hopefully more efficient LED strips.

Writing on LEDs with a laser pointer

After [Ch00f] got his hands on an 8×8 LED display, he didn’t make a 64-pixel video game or VU meter. He made a laser doodler, allowing him to draw on this display with only a laser pointer.

Using LEDs as light sensors is nothing new; [Forrest Mims III] discovered that LEDs can also detect light way back in the late 60s. [Ch00f] played around with this concept before creating a circuit that uses an LED as both a light emitter and sensor that reacts to the ambient brightness.

[Ch00f]’s laser doodler takes this phenomena and applies it to an Adafruit bicolor LED matrix. When a light shines on an individual pixel in the display, the ATMega48 senses the current and turns that pixel on. Since this these pixels have two colors, [Ch00f] used a latch circuit and a button to cycle between what color the ‘Mega writes to the display.

In the video after the break, [Ch00f] shows off his display by having the LEDs light up in response to a laser pointer. It may be a bit small, but we can see a lot of potential for something like this as a gigantic art installation.

Continue reading “Writing on LEDs with a laser pointer”

Heliowatcher positions solar panels for highest efficiency

[Jason Wright] and [Jeremy Blum] are showing off the project they developed for their Designing with Microcontrollers course at Cornell University. They call it the Heliowatcher, and if you know your Greek mythology we’d be you figured out this watches the movement of the sun and adjust a solar panel to follow it.

Their design is simple and effective. The base is mounted like a Lazy Susan, able to pivot on the horizontal plane. The bottom edge of the solar panel is mounted with two door hinges, with a motorized screw jack used to raise and lower it. The system uses a GPS to provide geographical position, day, and time feedback. This is used in conjunction with an array of four LEDs to determine the best position of the panel. Those LEDs are acting as light sensors; when the top and the bottom detect similar levels, the panel is at its most efficient orientation. The left and right LED sensors work the same way.

Now if we can just work out a self-cleaning system to keep the panels free of the dirty film that builds up over time we’d be set!

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Toilet Buddy helps cover up bathroom noises


When it comes to bathroom etiquette, [Nick] and the crew at Gadget Gangster are nothing less than proper gentlemen. Inspired by a Japanese toilet that automatically plays a “courtesy flush” noise in an effort to conserve water while masking sounds, they created the Toilet Buddy.

While the Toilet Buddy does nothing to cover up any aromas, it does provide some sound cover for those louder times. Not only that, it also helps serve as a reminder for other bathroom courtesies as well. When mounted on the tank lid, the Toilet Buddy alerts the last occupant to put the seat down and shut off the lights before leaving the bathroom. Built with a Parallax Propeller board, it uses IR and ambient light sensors to determine the position of the toilet seat and the status of the bathroom lights, playing an audio notifier when necessary. Now if it only sprayed air freshener automatically!

[Nick] points out that the Toilet Buddy is not limited to bathroom duty, and can be used in a variety of projects where light/motion sensing is required. Be sure to check out his writeup for some usage suggestions if you’re thinking of building one.

In the meantime, continue reading to see a video of the Toilet Buddy in action.

Continue reading “Toilet Buddy helps cover up bathroom noises”

Megavallometer camera trigger


[Tobe] has an intervalometer for his camera, but he wanted a device that could trigger the shutter using several different methods, not just time. He calls his creation the Megavallometer, which can utilize any one of three distinct criteria.

He recently purchased an Arduino and a couple of shields, so he figured this would be a perfect project in which to use them. He hooked up a microphone and a photodiode to the Arduino, allowing him to use both sound and light to trigger his camera, depending on which mode he selects. Of course, the Megavallometer still incorporates the functionality of a standard intervalometer as well.

Once connected to his camera he selects one of the three trigger programs, and the Arduino handles the rest. If either the light or sound triggers are selected, the respective sensors measure the ambient levels upon selection, allowing for accurate results in any setting.

While the Megavallometer is a bit larger than other intervalometers we have seen, it looks incredibly useful and can likely be strapped to a tripod or similar if need be.

If you have a minute, be sure to check out the video on his site for a sneak peak if his Megavallometer in action.

Add a shutoff timer to your bathroom fan

Adding this board (translated) to your bathroom fan will turn it into a smart device. It’s designed to automatically shut off the fan after it’s had some time to clear humidity from the room. It replaces the wall switch which normally controls these fans by converting the fan connection to always be connected to mains.  The board draws constant power to keep the ATtiny13 running via a half-wave rectification circuit. A single LED that rises from the center of the PCB lights up to signal that the fan is in operation, but it is also used as a light sensor, similar to the LED communications hack from a couple of days ago. When the lights go on in the bathroom the microcontroller will turn on the exhaust fan via a Triac. It will remain on until the light level in the bathroom drops.

There’s an interesting timing algorithm that delays the fan startup, and varies the amount of time it will stay on in the dark depending on how long the bathroom lights were on. This way, a longer shower (which will build up more humidity) will cause the fan to remain on for the base of five minutes, plus one minute longer for every two minutes the bathroom was in use. Pretty smart, and quite useful if your bathroom sees high traffic from several family members.

LEGO hand controller

[David Hyman] built this device to control a LEGO claw. One one end of things is the part you wear, that measures movement of two fingers and your thumb. On the other end of things is a LEGO claw with three opposing digits. You move, it moves. The claw uses light sensors and a gradient strip for position feedback. There is also an up-down wrist action that uses a touch sensor as the input. This is impressive enough to give the sniper rifle a run for its money.

[via Make]