This is an IR transmitter / receiver circuit I’ve made to control my TV, amplifier etc from my computer. It was made using a cheap Arduino clone, an IR module and an IR LED. The receiver can read most infrared remote controllers, independent of which protocol they may use.
Servo tester by 555 timer
I needed a servo tester for my workshop, to have at hand whenever I change servo horns or need to see if a servo is dead. I decided to use a 555 timer to do this.