Build a simple water detector and alarm

Did you know that many projects published at Elektor Labs include the word “simple” in their title? The one we highlight this week is one of them. Reading the project’s description reveals how you can transform a commercially available magnetic door switch into a water detector and alarm by adding just two resistors...

El-cheapo wireless doorbells across the globe are so unoriginal it makes you wonder how much more e-rubbish we can tolerate in and around our homes. Luckily, we electronicz people have the power and skills to design and build our own personalised contraptions, personal here meaning programmable not just at the MCU level but also at the musical level with crude yet original (or not, whatever you prefer) melodies.

The heart of our ultrasonic generator is a ATtiny25-20. To avoid the animals from becoming habituated, it generates a burst of roughly 1 second every 10 seconds. Since we humans cannot hear whether the circuit is active, an LED makes the operation of the circuit visible. The microcontroller itself is nowhere near capable of delivering enough current to drive a loudspeaker directly. So we added a BS170 MOSFET as a driver stage for the MPT-001 tweeter from Monacor.

Several companies sharing the same building all need a separate doorbell for visitors. The exterior of the buidling may not be altered. Do you have an original and high-tech solution?

I chose this video of the tinyTesla for both the nice shooting of the sizeable sparks and its soundtrack. Instead of presenting only the raw signal from the Tesla transformer, an accompaniment is played by other instruments using slightly softer timbres. The subtle contrast obtained by this orchestration is surprising and even the roughness of the tinyTesla tone becomes almost pleasant. Entertaining for budding coilers as well as for DIY electronics enthusiasts, this easy-to-assemble kit opens up a wide array of interesting operation and installation possibilities.

Engineers from the Rutgers University in New Jersey have developed an identification system that detects the vibrations in a finger in order to verify users. This clever security system called VibWrite makes verification of users possible when the fingers touch a smooth surface. The inventors think that this system can be cheaper than identification using a fingerprint or iris scan.

Here comes a dazzling DYI project allowing you to touch an electric arc (30 kV hey presto) with your bare fingers. No harm from that. Though powered by a mere USB charger, Spiral Micro Tesla generates spectacular and sonorous sparks. Instead of a large and potentially dangerous coil, Elektor presents this safe printed Tesla coil with limited energy, powered at under 5 V. The maximum power is 5 watts which can’t cause much damage, despite the staggering voltage.

Very common on old equipment, today they seem to have disappeared completely. I am talking about those pushbutton banks of which only one button could be activated at a time, like cassette player’s piano keys or channel selectors on radios. Thanks to a mechanical system pressing one button would release all the others that were pressed (normally only one). Today such tasks are handled by microcontrollers, but this project shows how to do it without. Four relays are switched by four pushbuttons, but only one relay can be on at any time. Add more channels to taste.

Connected Lighting is about networks of lamps, switches and other devices to form smart lighting systems for homes and offices. Mouser Electronics and Elektor have teamed up to bring you a free white paper on zigbee 3.0, the technology that makes Connected Lighting possible. We present not just the theory, we also shows you how to build a Wi-Fi/zigbee gateway with a Raspberry Pi and then set up a zigbee 3.0 compatible network to experiment with.

The differences in measurable potential on plants aroused the interest of Walter Polleros. His BioLight project detects electrical fluctuations which are then translated into a colour change of an RGB LED. This lightens the translucent pot in which the plant is located. Whether you are skeptical or enthusiastic, we are interested in your comments. Please restrain from calling names.