Communication over the IrDA port uses a relatively complex protocol but its possible to send a single character using just a few components. In many cases, this will be sufficient to control... Read more
Palm Pilots are just one of the devices that use the IrDA standard for infrared data communication. Most Desktop PCs are not equipped with an IrDA interface so this simple circuit convenient... Read more
Armed with a Smartphone you can surf the Web, send emails, text, chat, download and listen to music, take and post photos and video clips, listen and view TV stations, navigate, place bets a... Read more
Regenerative? What’s that? In the age of Twitter and smartphones, you can’t assume that things not related to the Internet are still generally known — or maybe they are? Amazingly, Google de... Read more
In many application areas, it can be very handy to be able to control something wirelessly. This circuit shows how an ATtiny microcontroller can be used to switch an appliance on and off rem... Read more
A shortwave audion receiver using only two transistors and a single 1.5 V battery — that must be the ideal entry level into shortwave receiver technology. Just add an active PC loudspeaker f... Read more
In the early years of radio technology, spark transmissions ruled the (air) waves. They occupied a relatively wide bandwidth, in what came to be known as the long wave band. The receivers us... Read more
This mousetrap is built around a PIC12F683 and uses an infrared transmissive optical sensor that is modulated at a frequency of 38 kHz so that it isn’t affected by the ambient light. The mod... Read more
Crystal filters are often used for IF filters in receivers, where the bandwidth of this filter largely determines the selectivity of the receiver. The unique feature of the filter described... Read more
Here’s a novel way of listening to bats over the Summer. Put the receiver — powered by four AA (R6) cells — on a window-ledge, for example, preferably aiming the ultrasonic detector towards... Read more
