Electronic products

Telephone ringer light

If you are lucky enough to have a big house, a large garden, and small children, this project just might interest you. It’s actually a telephone ringer capable of making any mains-powered device work from the ringer of your fixed line. With it, you will be able to control a high-powered siren or horn, as you like, in order to relay and amplify the low-level sound of your telephone (making it audible in a big house or in a large garden)! Alternatively, you can make a lamp light (or an indicator light) and so create a ‘silent ringer’ (helpful when small children are napping).

The other interesting part of this simple and inexpensive project is that it doesn’t require a power supply, contrary to similar items on sales in the shops. Before examining the drawing and understanding the principle involved, it is important to know that the ringer voltage on a fixed telephone line is pretty high. Since Europe and the EU Commission have not yet interfered, the exact value of this voltage and its frequency varies according to the country, but that’s not important here. The line carries direct current whether unoccupied or occupied.

Moreover, no more than a few hundred mAs needs to be stolen from an unoccupied telephone line to make the PSTN exchange believe the line is occupied. Therefore, capacitor C1 has the dual role of insulating this project with respect to direct current present on the line while unoccupied, or while occupied, while also allowing the ringer current to pass. The latter is rectified by D1 and clipped by D2 which makes about 6 V DC available to the C2 terminals when a ringer signal is present.
his voltage lights LED D3 which only serves as a visual indicator of proper operation as does the LED contained in IC1. This is a high-power photo triac with zero crossing detection from the mains, which allows it to switch the load it controls without generating even the lowest level of noise. This component, that we might just as well call a solid-state relay, was selected because it is comes in the form of a package similar to a TO220, a little bigger, and equipped with four pins. The pinout will not cause confusion because the symbols shown on our diagram are engraved or printed on the packaging. Since this circuit is not yet very common, we need to mention that it’s available from the Conrad Electronics website (www1.uk.conrad.com).

For the purpose of safe operation, the circuit is protected by a GeMOV on the mains side, called Varistor, VDR or SiOV depending on the manufacturer. The model indicated here is generally available. The load will be limited to 2 A, considering the model selected for IC1, which is more than sufficient for the application planned here. Finally, since a number of components in this circuit are connected directly to the mains power supply, the assembly should be placed in a completely insulated housing for obvious safety reasons.
Author: Christian Tavernier – Copyright: Elektor Electronics Magazine

Interval Timer kit

For intermittent operation of circuits and equipment. Blinking light, video/photo single frame shooting, slide projector control, miniature models. Specifications: * Output relay with dry switch-over contact: 3A/24V * Pulse time adjustable: between 0.5 and 5 sec. * Pause time adjustable: between 2.5 and 60 sec. * Power supply: 12V DC / 100mA * Dimensions: 1.6″ x 3.4″ More detail

Make and Learning Electronics by Discovery

This is Excellent Beginner Book for Hobbyists/Beginners/Makers Book.

Want to learn the fundamentals of electronics in a fun, hands-on way? With Make: Electronics, you’ll start working on real projects as soon as you crack open the book. Explore all of the key components and essential principles through a series of fascinating experiments. You’ll build the circuits first, then learn the theory behind them!

I recommend this book strongly for anyone just starting out in electronics. Many other books introduce the subject of electronics by talking about the early discoveries concerning amber rods, Leyden jars, and static electricity. This book dives right in using parts that you can pick up at a local Radio Shack, or can easily order on-line. And it uses a fun almost playful approach to experimentation. Your first experiment involves touching a battery to your tongue! Man, that will either annoy you into quitting or completely intrigue you into learning more. My bet is it will spark (pun intended) your interest and excitement as it leaves you with a funny metallic taste.

This is exactly the hands-on approach that I was looking for to teach my son. Something that he can read on his own, or read with me. Easy experimentation, clear steps, good photography. No wondering if any of the experiments will fail because they were written only/mainly to think about. These were all written to be DONE by the reader. Getting into the nitty-gritty of learning is easy when you can actively experiment as you learn.

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