SR latch
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange users link it when explaining or copying how feedback in logic gates creates latching behaviour and the power-up state of an SR latch.
Recommended by 1 people across 1 different months, 2017 to 2022.
What it is
Ben Eater builds an SR latch on a breadboard, starting with a single OR gate whose output feeds back to its input, then moving to cross-coupled NOR gates. He wires up 74LS32 and 74LS02 chips with buttons and LEDs to show how feedback turns plain logic gates into one bit of memory.
What people said
Recommends Aaryan Dewan · 2020-10 · Electrical Engineering Stack Exchange · on “In a NOR gate not connected to any power supply, how can the output be '1' if both of the inputs are '0'?”
For people who have the same question but are not quite satisfied by the answer given, see this video: [this video] . Here, just before connecting, the O/P was 0 (which should have been 1) but as soon as he powers the thing up, even though no current flows as I/P, the O/P is 1 (as expected)
Cites John Joe · 2017-12 · Electrical Engineering Stack Exchange · on “Why does a 2-input OR gate cause the input to stay on when there is feedback?”
As I understand it, latches are made from OR gates, but I am trying to understand the basis for how they work and came across this video [this video] . When you make simply one OR gate with two inputs, A and B, except that the input B is the feedback output, you get a latch that doesn't reset. At around 3:00, he demonstrates that when you turn the button on, it stays on forever and that you can only reset it by creating an open circuit. But, why does the output stay high forever just because the input was high one time?
Cites Jack Moore · 2022-03 · Electrical Engineering Stack Exchange · on “Unclocked NOR gate SR latch not latching”
I am starting to learn computer architecture and decided to try building an SR latch using NOR gates and without a clock (basically copying this [this video] video) on a breadboard. My circuit is pictured, it is using an SN74LS02N IC for the NOR gates and I am powering it using a micro USB wire connected to a 5 V wall plug. I have confirmed that the IC is receiving 5.07 V, so it is within the operating range. However, when I press the set button (bottom button), the top light initially turns on, but then it turns off, either when I release the button or a few seconds after I release it, with the bottom light turning back on. I've tested around with the voltmeter and the main issue I have found is