# Tagged Questions

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### How can a logic gate work with multiple signals if a circuit only (supposedly) uses one electrical line?

On, say, a circuit for a lightbulb there's only one line for the current to flow, and that current is illustrated in every circuit I have ever seen. Being a beginner to this I am wondering how that ...
43 views

### Minimum #states in State Transition Graph [on hold]

I have the following question at hand regarding a sequential circuit: Can someone please help me solve this question? It is not a homework question. I was preparing for an exam and I was solving ...
80 views

### Interpreting a digital logic diagram [on hold]

I wanted to know the meaning or how to interpret the inputs to get the expression for the output f? Can someone please help me out?
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### Design a circuit using only 2 to 1 multiplexers that implements the function of an 8 to 1 multiplexer

I'm not entirely familiar with multiplexers and I don't fully understand the concept of how I can make a 2 to 1 imitate a 8 to 1. Is there a predetermined/default truth table for multiplexers that I ...
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### How to cycle through outputs ONLY given clock signal?

Purely using digital logic devices (no microcontroller) I was hoping to create something that will cycle through its outputs (only 1 pin high) given only a clock line. Daisy chain flip-flops? I ...
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### If digital logic requires a digital signal, does a computer's PSU have to make the signal digital before starting? [closed]

We know that the 120v from the wall is analog ... it looks like this: And the digital one that the components will use (transistors, diodes, etc.) will look like this: That would imply that an ...
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### Component Advice - Single Digital Line Cutoff

I have a command signal +/-10V 20mA (max) is going to a motor controller. The command signal is varied using a National Instruments I/O device but the problem is that stopping the LabVIEW program/VI ...
61 views

### IGBT Logic Switch

I am trying to make a switch with an IGBT STGP19NC60HD. Here is a link to the data sheet. My simple circuit looks like this: simulate this circuit – Schematic created using CircuitLab Im ...
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### Issues with 4-bit counter when porting to PCB

I need help or maybe an explanation on a particular issue I am experiencing when porting a small and relatively simple circuit from a breadboard to a PCB. The circuit is for a school project used to ...
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### Building a toggle with a flipflop?

I'm trying to build a toggle that turns a 4 bit counter on or off. Here's where I'm at so far: As you can see, I'm using a single D flip flop. Ideally I want one switch to disable the chip, and ...
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### Recommended voltage/current for dry contact input?

What would be a reasonable value for voltage and max current to used in conjunction with a remote dry contact output so that it can return to my MCU (through isolator)? I plan on using this input for ...
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### How to wire up optocoupler for digitally controlled UV (under voltage) input protection?

What I am trying to build is an under voltage input protection. It will always limit the voltage flowing into the output end to the microcontroller to be 3.3V, but when the input goes below 380V, it ...
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### How to extend this particular multiplexer circuit to 4 x 4 channels in / 1 x 4 channels out?

How to extend this particular multiplexer circuit to 4 x 4 channels in / 1 x 4 channels out? Forgive me my ignorance, I'm just a my very beginning with this stuff... Thank you!
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### How do I simplify this sum of products expression into an easier sop form

'=Compliment D=P'VST + PV'S'T + PV'ST'+ PV'ST + PVS'T' + PVS'T + PVST' + PVST I'm having trouble simplifying this.
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### Dealing with digital circuits and their associated switching speed?

When designing a digital one-minute counting circuit I came across a difficult problem. Basically, I designed the circuit to drive the (normally HIGH) clock of the 10s slot low if the 1s slot's ...
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### How is Crystal Oscillator implemented in digital circuit to generate clock frequency. What part of crystal oscillator makes the clock signal?

How is Crystal Oscillator implemented in digital circuit to generate clock frequency? What part of crystal oscillator makes the clock signal? I know the fact that crystals has its resonating ...
60 views

### Logic-circuit physical implementation

I've got a logical design that uses roughly 3000 NAND gates. So far it's only on simulation, but I would like to physically implement it. The circuit is already simplified. What are my options to do ...
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### How do I use multiple BCD switches as a single binary input?

I'm trying to convert a 4-digit (decimal) number to binary. My input is a BCD switch (this one). I've been looking to see if I can find either a logic-based circuit or a specific decoder IC to convert ...
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### Motor polarity reversing circuit using just SPDT switches

I have a 6v DC motor that controls a physical system similar to a window blind, using one SPDT toggle switch and two SPDT microswitches for control. I have seen similar setups with hoists, however I ...
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### How does the basic RS Flip-Flop (also known as latch) works?

Ok this is a basic question but i am not able to figure out how does this work 1: This is the representation of the RS Flip-Flop with the truth table given in my book I am not able to connect the ...
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### Learning Curve For Microcontroller Programming & Anlog/Digital Electronics? [closed]

What is learning curve for embedded developer in which you can learn with doing small projects? I'm working in a power electronics firm. Our product portfolio is Inverters/Converters, Chargers, AC/DC ...
106 views

### Vegetable oil controller?

So I have been working for a while now on a controller for the vegetable oil system in my vehicle. I am fairly new to programing and am enjoying teaching myself with an arduino. I have an arduino nano ...
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### Is PIC running at 3.3v, 5V logic tolerant?

Can a micro-controller that is capable of running at voltages ranging from 2.3 to 5.5 V, tolerate 5V logic levels while operating at 3.3V? I need to interface GPS (5V) and raspberry Pi (3.3V) with my ...
109 views

### Flip flop with load/set, reset, clk, and input

I'm not looking for a hardware language description of the flip flop, but the logic gate level to implement. In verilog, the equivalent I'm looking for is ...
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### How to cycle through bits of information for a hex display?

I am doing some work with a Hex Seven Segment Digital Display with a built in decoder that takes in 4 bits of information. Controlling it I have 4 cascading T-FlipFlops whose outputs are inverted so I ...
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### Convert area of ASIC into kilo-gate equivalent kGE

Is there any resource/datasheet where I can find the kilogate (kGE) of the various CMOS technologies? Essentially, I have a bunch of ASIC circuits with their areas given in mm2 that I want to convert ...
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### How many gates does a 7400TTL decice have? [closed]

How many gates does a 7400TTL decice have? What type of devices inside this chip?
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### Allowing a BJT to turn on and turn off at different set points

simulate this circuit – Schematic created using CircuitLab The circuitry I have on my board currently is the schematic above. It is showing a start up regulator. D1 is an 18V zener, as ...
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### Reset and clock

In digital circuits (combination & Sequential) which input holds more priority clock signal or a reset signal? suppose we give a input reset in an asynchronous counter then reset will wait for ...
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### What if setup/hold time is not violated but data becomes valid outside of the normal data valid window?

Lets look at the latching register in register to register path. Usually there is a skew between the latching register clock and the launching register clock. The latching register clock is delayed in ...
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### Digital Logic and Assertion levels

I'm struggling to get my head around assertion levels and how it relates to logic levels / functions. For example. Let's say we have 2 input signals, A and B So A assertive high and A assertive ...
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### What do 2 pairs of three numbers separated by colon mean in SDF files when describing delays of cells?

OK here is an example: ...
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### Simple state machine's state table

EDIT: This is a homework question. What I need to know is how to solve the circuit through the transition table. That is, how do I write the circuits for the state changes (is it a flip-flop circuit, ...
90 views

### ATtiny/ATmega programmer board - need a 6 x 1:3 Mux solution

Hey so I'm trying to create a circuit on perf board that allows me to program three different types of chips using an Arduino Duemilanove as ISP. Those chips are the ATtiny85, ATtiny84, and ...
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Sometimes, if the sum of two digits are < 10, BCD addition is similar to binary addition. But sometimes if the sum > 9, the result requires a correction. This corrections is +( 0110). Why do we ...
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### Exclusive control over actuators

I feel kind of stupid asking this question, but after unsuccessfully searching for papers and then starting to draw my own solution with a lot of XORs to the following problem, I started wondering ...
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### QuestaSim/ModelSim simulation gives me unkown value in wave window. However I get them as X and x, what is the difference between the two?

What is the difference between big X and small x when we get red (unknown) signals in QuestaSim? I would assume it to be the same in ModelSim simulation as well.
125 views

### Implement a Function using 3x8 decoder (74LS138)

I need to implement the function below using 3x8 decoder (74LS138) and a minimum number of gates but I did not see 74LS138 before. F = (A.B)' I implement the function using a normal 3x8 decoder but ...
339 views

### How to build an interesting XOR circuit with my child's electronics kit

When I got home today, my child was proudly telling me how they had managed to make AND, OR, and NOT logic from his snap circuits electronic kit and was asking me how they could make exclusive or. ...
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### What are “Equivalent Logic Elements”?

I'm browsing through the specs of Arista's Stratix V FPGAs. The first row of Table 1 is labelled "Equivalent LEs". What are "equivalent logic elements"? What "logic element" do they use as a ...
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### How to find Gate Delay

I need to find the delay of a full adder. I searched for it but I couldnt find absolute information. Sample delays : XOR - 8ns / AND - 2ns / OR - 2ns What is the delay of this circuit? My Solution ...
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### Circuit to emulate 2/3 button presses

I am attempting to build a simple circuit to to control sound on my Android phone. All the controls are accomplished by tying a control pin to ground, so all I do in between is just about resistance ...
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### Confused about Full-Subtractor truth table

I'm a little confused about the 011 condition in the Full-Subtractor truth table. I don't get how the output can be D = 0, B = 1. Since D = A - B - C, that gives D = 0 - 1 - 1 = -2 How does a ...
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### General guidelines in making a choice between Combinational or Sequential approach?

I have to design a functional unit, which can be done either using Sequential Circuits or combinational. I have to make a choice. Development time is not an issue, but resource usage and space ...
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### Usage of “safe” gated SR Latch?

I just learned about SR Latches, D Latches, and their gated versions and I've got a little burning question. So of course with the SR Latch, the professor told us that the "11" condition cannot occur ...
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### Best way (logic) to model an XOR?

Some people say that the best way to model an XOR is to use NMOS pass logic. Others say its better to use a transmission gate (or simply, pass logic). The only difference I could find in these ...
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### Is it possible to combine independent digital TV antennas?

Is it possible to create a TV antenna that is composed of smaller antennas that are pointed to different broadcast centers? So in essence, many antennas for just a single digital TV. Is it possible ...
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### How digital video is processed? [closed]

I'm not sure if I'm using the right words, but I would like to learn how digital video works. I have a book that explains how VGA works and how to implement it on FPGA. I would like to know what kind ...