Questions tagged [latch]

A latch or flip-flop is a circuit that has two stable states and can be used to store state information. However latch is normally used to describe a simple storage device while flip-flop is normally reserved for clocked devices.

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Weird thing happening with my latch circuit [closed]

I was experimenting with this basic latch circuit where you have an NPN transistor opening the base of PNP transistor to GND, and once the PNP is on, the collector latches into the base of the NPN, so ...
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MAX31865 data readout in continuous conversion mode

Reading the MAX31865 data sheet, it remains unclear to me when / how conversion results are latched in automatic (continuous) conversion mode. Figure 9 shows how /DRDY is set (it goes low when new ...
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SR latch circuit with ESP8266

I want to keep some state during a deep sleep of an ESP8266. To do this I used the following SR latch circuit: It works well. The only change I made is that I used 2N2222 transistors. The only ...
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Soft Latch ON-OFF with support of DC High Voltage side, compatibile with Arduino or any Low Voltage MCU (with schematic)

First Schematic I'm trying to implement this schematic that I found in this interesting article (Soft Latching Power Circuits). This is a circuit can substitute a mechanical on off switch, and use ...
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24V input shutdown-latch - is it a good idea?

I want to protect my circuit by adding the ability to the MCU, to turn-off the power supply (and by this also turn itself off), in case of certain failure conditions are met. One of it would be ...
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What kind of latch would be best to continuously store and feed in a series of inputs?

So I've got an assignment where I've two buttons and LED screen. One button inputs a '1' and the other a '0', and when four inputs are detected the screen displays the number eg. If I typed 0011 it ...
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Toggle latching IC to replace relay

I need an IC on which pins stays in same state after power reset. How it's called? I don't want to use relays.
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Unclocked NOR gate SR latch not latching [closed]

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 video) on a breadboard. My circuit is pictured, it is ...
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6 answers
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Doubt regarding SR latch

I am having trouble visualizing an SR latch intuitively. Here the two outputs \$Q, Q'\$ both are dependent on each other,so how will the two function at the same time? Let me break it down. Suppose I ...
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How do I make a NAND SR-latch with transistors

I'm trying to make a NAND SR-latch using only transistors, by combining a schematic for a NAND gate and a schematic for an SR-latch. The resulting circuit looks like this: (One thing not shown is ...
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3 answers
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Switching between power sources part 2

So I'm trying to switch between two power sources, a 24 V battery and a 24 V power supply, I'd love to use the circuit mentioned in a another thread. Switching between two power sources I am having ...
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How to understand this combinational cyclic circuit made of interconnected SR latches?

I'm trying to understand the following circuit, or better said, what must be the approach to analyze other similar ones: What I'm doing for now is forget about the clock signal and the ...
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Latching an analog signal on a trigger event

I am looking for sort of an analog equivalent of regular digital latches. I want it to mirror its input (voltage) to its output (voltage, with or without gain) only at a trigger edge/pulse and ...
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Does an eFuse exist that latches off immediately (and does not reactivate) in case of a short-circuit?

I've just discovered eFuses (from Texas Instruments + Toshiba + STMicro). In case of a short-circuit on the output, MOS can be disabled in 150-500 ns by detecting a surge of current (called "fast-...
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Latch the values generated by a 4-16 line decoder

I am using a 4 to 16 line decoder to convert a 4 bit number from arduino/seeed/ESP32 to drive circuits like RGB leds which would otherwise use up all my pins. There are some problems with this ...
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Finding a pass-through demultiplexer with latch/register on output

I'm currently working on an Arduino project with lots of digital IO (21 outputs, 8 inputs) and no analog IO. This is more than the number of digital pins on an Arduino Nano, so I started looking at ...
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To turn a ratioed circuit into non-ratioed circuit, what should be the transistor sizes for proper operation of this circuit?

The circuit is at the bottom. I know it is a ratioed circuit however, how can I convert it to a non-ratioed circuit without adding two more PMOS transistors between Vdd and the other PMOSs. Also, what ...
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Identification of a circuit element

Here is the image: What does the triangle with a bubble on one of its sides represent?
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Is there a simpler way to latch a supervisor?

I’m currently designing a Li-Ion powered ESP32 circuit. The ESP32 has a minimum operating voltage of 3 V. So, my instinct is to use a 3.1 V supervisor to keep the ESP32 within an acceptable range. ...
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Valid Use of Voltage Divider Supply?

I know it's not a good practice to use a voltage divider as a power supply, but I'm considering it for an unusual circuit. Is this a good use of a voltage divider or is there a better way to do this I'...
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2 answers
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How enable for latch converts to clock in flip flop [duplicate]

Latch has enable signal and we cascade latches to make flip flops. How enable for latch converts to clock in flip flop. I mean how and why enable driven latches form edge triggered flip flops. Why ...
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How to make this T-flip-flop circuit

I am trying to make a T-flip-flop circuit with a relay, which would: toggle on a button press (12 V) [default state: off] allow control from an external micro-controller (optocouplers) allow ...
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How to stabilize this CV triggered toggle (555 timer latching switch) when fed with two gates?

I created the prototype for a modular synthesizer module. The project goal is an AND gate that is fed with two control voltage inputs (A and B with an Vpp around 5V). There will be two outputs: the ...
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3 votes
3 answers
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How does an SR-latch actually work?

In case of a NOR SR-latch, if we make S = 0 and R = 0, then output Q = 1 and nQ = 0. I also know one important rule which is if we put high input in the set line (S = 1) then output Q goes high. If S =...
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Why isn't my SR latch working?

I built this SR latch out of two NOR gates. However, it doesn't seem to be working for some reason. Why not? (Created with TinkerCAD) Here's a circuit diagram (source is 5 V):
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Making a register from DFFs without using multiplexers

I am currently trying to design a 4-bit register that is optimised in terms of transistor count, since I will be laying it out in a larger circuit that is very limited in terms of chip space. My ...
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2 answers
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Converting latching switch to momentary output

I'm trying to get a latch switch to send a pulse for around 3 seconds or so. The pulse doesn't need to be pretty or precise. The circuit will be used to sound a buzzer when the switch is flipped on. ...
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Car soft latch circuit auto triggers

I wanted a circuit to power on and off the front parking sensors of a car with a single button. After searching the internet for a bit I came across a soft latch circuit by eevblog and after changing ...
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1 vote
1 answer
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Logic gate latch application question

I am trying to design a reliable latch to lock the output of U3 permanently high when the Q14 goes high and I couldn't find a solution after searching online, so I came up with the following circuit ...
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2 votes
1 answer
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555 Timer Switch Circuit Operating at 12V Problem

I have designed a prototype PCB for a product we are working on. It works, but with minor problem the PCB should be able to be supplied from anything from 5V - 12V. The problem is the 555 timer ...
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2 votes
4 answers
120 views

Switching on and off at different voltage while maintaining states

I am designing my own circuit to switch on / off a 9V motor via solar panel. I am connecting 2 sets of 3.7V 18650 batteries in series, that means the circuit runs on 7.4V. I am also using a generic ...
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How do I develop a discrete SR latch into a simple shift register?

I trying to develop a discrete SR flip-flop into a serial in parallel out (SIPO) shift register, say 2 bits for the sake of learning. I don't have a clue how to proceed. For the SR latch, I suppose I ...
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1 answer
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Why is my latch circuit not toggling?

While I am waiting on some parts I made this circuit in a simulator. When S1 is pressed it should toggle the relay K1 and latch in that state, turning on the other LED. When I press the switch, though,...
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5 votes
3 answers
160 views

Put SR latch to determined state during power on

I'm trying to build a circuit that will stay turned on once triggered, and ordinary SR latch seems like a perfect solution. However, I cannot find an efficient way to turn SR Latch to deterministic ...
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1 vote
1 answer
106 views

Can we detect moving "in" and "out" without timers? [closed]

I wish to automate my light-bulb such that when I enter it turns on and turns off when I exit. So there are two sensors A and B. A then B : Light ON B then A : Light OFF I was wondering if it is ...
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1 answer
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Break Before Make Implementation [closed]

I want to add a circuit after comparators, so that the outputs of the comparators don't be high or low simultaneously. i.e., if the first output goes high, the second output should be low. And if the ...
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Is the the output of Q' in an S-R Latch used for anything, or is only the Q output important?

From looking at a diagram like this: and watching some videos on the topic, it seems that Q represents a 1-bit memory, but I'm unsure if there is a purpose for Q'.
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Shared rising edge detector? [closed]

Why do we have a rising edge detector in every flip flop of a register. Can't we just make a shared one for all the flip flops in order to save hardware?
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Combinatorial loop of SR latch

I implemented an SR latch in Verilog. module sr_latch( output Q, output P, input S, input R ); nor(P, S, Q); nor(Q, R, P); endmodule However, ...
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How to find the capacitance at a point?

I wanted to find the capacitance at X,Y,P and Q in the diagram given below. Idea was to find the dynamic power consumption of the circuit and for that we need the capacitance(I got this idea from a ...
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3 votes
2 answers
172 views

VHDL -- K-map reduced characteristic equation fails

I have this circuit (D-latch): and I can directly write the logical equation by only watching the gates: $$ Q = \overline{(\overline{(D \cdot C) + Q}) + (C \cdot \overline{D})} $$ If I want to ...
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Need help on latching circuit turning on without pressing on/off button when battery is inserted

I have this latching circuit to turn on and off an MCU (ATTINY 167) and a led Driver, by using a 8.4V Lipo battery. It works fine: pressing the button turns it on and pressing again turns it off. Also,...
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2 answers
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Need help to bypass the momentary switch in this latching ciircuit (but keep using it.)

I’m using this circuit to turn on and off an Attiny167 and an LED driver with the push of a micro switch. My circuit is powered by an 8.4V battery. In the “load” part of the circuit there’s a voltage ...
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1 answer
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Low current power cutoff for microcontroller

I'm attempting to design a battery-saving circuit for a microcontroller/computer. I plan to hook the circuit up to a raspberry PI and have it cut the power completely once it is fully shut-down. The ...
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Active high SR latch when input changes from (1,0) to (0,1)

If we do analysis like in the below diagram i.e from S side, then I got outputs Qn+1=0 and (Qn+1)'=0. But it is not supposed to happen according to state table( i.e actually Qn+1=1 and (Qn+1)'=0 must ...
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3 votes
1 answer
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Question on timing diagram of a SR Latch with different gate delays

Below is the verilog code that I wrote to implement a simple SR Latch. Note that I assumed different gate delays for the same NOR gate. (#10, ...
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Transistor as a switch from point A to point B

[ Hello, I'm curious how I could replace the momentary switch with a transistor in this scenario. Would I connect the left side of of the button to the collector and pins 2 and 6 to the emitter, then ...
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Cycle-by-cycle current limiting with latching comparator

I am attempting to design a cycle-by-cycle current limiting circuit for a motor driver. Here is my circuit along with some notes to explain its intended operation: The latching comparator I plan on ...
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1 vote
2 answers
92 views

What is the simplest logic circuit + latch that satisfies this truth table?

This is not a homework problem, I'm just revisiting/relearning the practical applications of latches and logic circuits and I've been trying to figure this out on my own. Basically, I want to turn one ...
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3 votes
2 answers
274 views

How to turn a Latch circuit from Press-ON/Press-OFF to Press-ON/Hold-OFF circuit and how to make it auto-off when power is first connected?

I'm building a Latching circuit using 555 IC. The schematic is as follows: The Input voltage is 12V and is used to operate the 555 IC that switches a relay coil through a transistor. When the circuit ...
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