This is Electronic Stethoscope circuits. Usually the stethoscope is a medical device that listens to the heartbeat. Which we can make it with the least amount of electronic equipment so easy to make.
My son wants to know more about MOSFET. I recommend trying to create simple Time Delay circuit using MOSFET,easy to make and long time and less parts than normal transistor. because working with voltage gate.
This is first mini emergency light of my son. It is very small, use LED display when power outage,use transistor instead relay use AA battery charger.
The siren circuits are what importance in various alarm system. For example, the emergency alert, burglar alarm circuits, Fire alarm circuits, Timer , sensor controls, etc. Today I would like to introduce the simple and economical simple siren circuits. It is suitable for beginners. My son will gradually build this circuit onto the PCB layout. Look at below! 4 Circuits.
This is simple signal injector circuit, used two transistors join together as astable multivibrator, signal output frequency 1,000Hz in square wave form.