This circuit generates a tone that sounds very similar to a siren. The generator part of the circuit is made of the combination of PNP and NPN transistors. Toghether, the two transistors build up a ...

We must admit that we’ve been guilty of using a microcontroller to make two LEDs blink alternately in the past. It’s not the worst transgression, but it stems from our discomfort with analog circuits.

Here is the circuit of an ultra sensitive IR receiver that can be used to switch on various AC devices through an IR transmitter. It uses the Photo transistor L14F1 to detect IR signals from the ...