Smart Loop Burglar Alarm

Simple loop burglar alarms sound whenever the loop breaks. What if a clever thief comes to know of the working of this alarm? He may simply short the loop by using...

CAR-REVERSING HORN WITH FLASHER

Here is a simple circuit that starts playing the car horn whenever your car is in reverse gear. The circuit (refer Fig. 1) employs dual timer NE556 to generate the sound....

Stereo Headphone Amplifier

Here is an inexpensive circuit for a stereo amplifier to drive a low-impedance headphone set. The circuit uses a few cheap transistors (BC547 and BC557) and passive components like resistors, diodes...

Whisker for Robots

Whiskers for robots are simple switch-type sensors that work like an animal’s whiskers detecting nearby objects in the environment. When disturbed, the sensor sends a pulse to the robot to indicate...

TRANSISTORISED LOGIC PROBE FOR TTL

A logic probe is a handheld pen-like probe used for analysing and troubleshooting the logical states '0' or '1' of a digital circuit. While most logic probes are powered by the...

INVERTER FOR SOLDERING IRON

Here is a simple but inexpensive inverter for using a small soldering iron (25W, 35W, etc) in the absence of mains supply. It uses eight transistors and a few resistors and...

LED And Luminaire Testing Can’t Be Taken Lightly

Standards and tests are essential to evaluate the quality and longevity of LEDs and luminaires. So test and measurement solutions have to keep pace with the evolving LED lighting standards SHWETA DHADIWAL...

Design And Test Challenges Of Frequency-Hopping Radios

The erratic behaviour of frequency-hopped signals makes them difficult to capture, verify and measure. Hence more effective tools and processes are required to design and test modern radios that employ increasingly...

Looking Into The Brain For Lie Detection

Though the reliability of brain scanning for lie detection is still under question, these tests are fast becoming popular with the crime investigating teams. Here’s how they work DR S.S. VERMA Police use...

MULTI-SWITCH DOORBELL WITH INDICATORS

Here’s the circuit of a multi-switch input musical doorbell (shown in Fig.1). The circuit is built around the popular and less expensive quad D-latch CD4042B (IC1). When switch S6 is pushed to...