Digital Logic - SR Latch




The SR Latch is a great way to introduce how digital logic works. First you make two NAND Gate which is "Not AND" in logic terms and you can combine them together to make a latch. The way it works is by using the unstable condition to hold the last state or the last pushbutton that was pressed. This introduces memory into the circuit.

Part List

  • Pushbuttons (2)
  • Green LEDs(2)
  • 1,000 Ohm resistors (10)
  • NPN transistors (4)
  • Diodes (6)

How it works

Just press the top pushbutton and the top LED will stay on or press the bottom pushbutton and the bottom LED will stay on.

If you would like to learn more visit



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    This looks like an awesome gadget, I just wish there were more pictures, and more step by steps. Those two things can really help people fully complete your project!