The ultrasonic hand sanitizer circuit detects the presence of human hand through reflected ultrasonic waves, and triggers a relay solenoid pump momentarily for dispensing the sanitizing liquid on the hands of the user. The project uses the popular HC-SR04 ultrasonic sensor module for the required sensing function. Using HC-SR04 The HC-SR04 ultrasonic sensor module is […]
Archives for 2020
5 Simple Fastest Finger First Circuits Explained
The 5 simple fastest finger first indicator circuits presented here can be used for indicating which candidate was the first to press the answer button out of the 4 participating candidates in a quiz contest. We all have probably seen the famous game show “who wants to be a millionaire” and many similar quiz shows, […]
Unijunction Transistor (UJT) – Comprehensive Tutorial
A unijunction transistor is a 3 terminal semiconductor device which is unlike a BJT has only a single pn junction. It is basically designed to be used as a single-stage oscillator circuit for generating pulsed signals suitable for digital-circuit applications. UJT Relaxation Oscillator Circuit The unijunction transistor could be typically wired in the form of […]
Solid State Relay (SSR) Circuit using Two MOSFETs
SSR or Solid state relays are high power electrical switches that work without involving mechanical contacts, instead they use just a couple of solid state semiconductors like MOSFETs for switching an electrical load, smoothly, and with high efficiency. SSRs can be used for operating high power loads, through a small input trigger voltage with negligible […]
Diac – Working and Application Circuits
The diac is a two-terminal device having a combination of parallel-inverse semiconductor layers, which allows the device to be triggered through both directions regardless of the supply polarity. Diac Characteristics The characteristics of a typical diac can be seen in the following Figure, which distinctly reveals the presence of a breakover voltage in across both […]
How Contactless Infrared Thermometers Work – How to Make One
In this post I have explained the basic working concept of thermal scanners or contactless IR thermometers, and also learn how to make a practical DIY prototype of the unit without Arduino. In the post COVID-19 era, witnessing doctors holding a contactless temperature gun and pointing toward the forehead of a COVID-19 suspect is a […]