Hi, im building a light switch with a infared led, when somebody put the hand between the led and the sensor, the circuit will send a signal to a relay, and then turn on the lights, my problem is, i want the the circuit stays on, even when the hand is removed, and when somebody pass the hand again, the lights turn off. Well, i have to to this without use ant IC`s, just logic gates, transistors and the basic components of eletronics... i was thinking in build a memory circuit with logic gates, but i dont figured out how do it..
obs.: i can use the ic 555.
