Digital electronics use a finite number of states, unlike analog electronics that treat continuous signals. Digital logic is used to perform arithmetic operations with electric signals, and constitutes the base for building CPUs.

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25 views

Circuit to keep two LEDs on when buttons are released

I am trying for the first time to build something on my own. I am pretty n00b when it comes to electronic so, please, bear with me. I'm trying to build a "simple" schematic that goes like this: there ...
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0answers
41 views

Is it safe to use a bus buffer as level shifter?

I am currently using SN74ABT5402ADW as a buffer and level shifter for my ADC, however, the datasheet does not explicitly say that it can be used as a level shifter. I provide it with 5V power, but the ...
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5answers
782 views

Can an operational amplifier circuit be made entirely out of diode Nand and Nor gates?

I'm not sure whether this question has been asked before, but in researching my question, I came across this user's post (at If-else decision structure using op amps or any other non-programmable ...
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0answers
59 views

What is bit-true implementation

What is bit-true implementation (with an example if possible)? I was reading a paper and it was stated "a bit-true implementation of the algorithm on a FPGA was performed." So what exactly is ...
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3answers
91 views

Should I use CMOS vs. TTL?

Now, I know that this question has been asked so many times that it seems like I'm trolling, but I must point out that I couldn't find the right answer to this question anywhere. So yeah, CMOS and ...
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1answer
37 views

fpga verilog dual access

I need to write to a register from 2 sources.. in this case, a pci host and a microcontroller. The 2 will never access the register at the same time (basically once the PCI is done , it hands it ...
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1answer
42 views

Registers and Busses

I need to design a schematic for a register that has an input of clk and i[7:0] which is an 8 bit binary input interpreted as a number and an output of F which goes high if i was equal was to 127 base ...
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0answers
46 views

Can you calculate parasitic elements caused by using many breadboards?

Recently, I've had the idea of building a 4-bit CPU out of RTL (Resistor Transistor Logic). Because there are so many connections, I would prefer to build this project on many breadboards. I realized ...
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2answers
290 views

I/O series resistor

I've read that digital I/O pins should have a resistor in series in order to limit noise. Should one also use such approach when interfacing with the I/O pins of an arduino, or is that already done on ...
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1answer
52 views

Digital light organ

I am trying to make a circuit that takes an audio signal from an MP3 player and converts the signal into digital signals based on frequency. Audio In is the is the signal from the audio jack of an ...
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6answers
1k views

How does a non-FPGA (ie a PC with a CPU, RAM, hard drive) mimic logic gates?

I know that an FPGA uses look-up tables (LUTs) to synthesize logic gates. A LUT is a block of RAM that is indexed by a number of inputs. The output is the value stored at that memory address. The ...
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2answers
88 views

Isolating an analogue input using ADC/DAC

I'm looking into isolating an analogue input coming from field equipment and interfacing to a PLC analogue input module. The input will be of the 4-20mA range (1-5V). There are a few ways to approach ...
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1answer
46 views

How can I measure a three phase current using a digital multimeter?

My multimeter does not have provision for AC current measurement. Can I use a CT with my digital multimeter to measure three phase current? If so, how can I do it?
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1answer
118 views

What is this quadruple triangle logic symbol? [duplicate]

Or maybe it is two mirrored triangles... and an 'invertor' dot? This is from a diagram in the ATMega328P datasheet, page 76 bottom left. Note that this question shows a similar device. In that ...
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1answer
61 views

How does digital patch memory work on an analog synthesizer?

Not an electrical engineer, but kicking around ideas for a polyphonic analog synth with digital memory, a simplified/modernized update of an older all-analog design. I've riffled through some of the ...
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1answer
66 views

What is the ideal resistance for a 2N3904 base resistor value when using RTL logic?

I have a ton of 2N3904 transistors and would like to use them for my RTL logic project. Based on what I could figure out on the web, and the parts I had, I've gotten logic gates to work quite well ...
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5answers
150 views

Kinds of Feedback

"Feedback is a process in which information about the past or the present influences the same phenomenon in the present or future" I find the idea of feedback quite fascinating and i could ...
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0answers
24 views

conformal renaming rules: Mapping

I had around 140 extra points which were unmapped after mapping key points. Signals have this format signal[5] -> signal_5_0 abc[5]_z -> abc_5_0_z So I ...
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2answers
63 views

Fan in Fan out problem

Fan out is the maximum number of inputs that can be connected to a specific output. Why can’t we connect more number of inputs to this output?
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0answers
23 views

Timing Issues When Interfacing with E28F800 Flash Chip

I'm trying to interface with an E28F800 via an Arduino Mega and am having trouble trying to program it. I'm successful in reading off the chip by toggling CE# & OE# while asserting an address, but ...
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0answers
20 views

Can a retroreflective sensor detact a Charged coupled/CMOS /digital camera?

I am working on a research project and just wanted to know if a retroreflective sensor detect a Charged coupled/CMOS /digital camera?
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1answer
40 views

Finding the minimum switching expression for this output

Did I do this correctly? ...
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3answers
155 views

74154 4 to 16 decoder logic diagram

Will someone please explain the purpose of inverting the outputs (0 through 15) as well as the use the NAND gates here? 2nd, less important question: why are there two input G1 and G2 if the ...
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3answers
73 views

In a NOT gate circuit, does charge not flow through both the transistor and output line when the transistor is “on”?

I've tried to recreate a circuit from what I think would be a NOT gate, based on some other schematics and breadboard examples that I've seen. simulate this circuit – Schematic created ...
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2answers
109 views

What's the point of putting two NOT gates sequentially? [duplicate]

I found the following diagram in data sheet for M74HC595 8 bit shift register I have three questions. Do I understand correctly that all blocks inside red ellipses are NOT gates? What is the ...
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2answers
75 views

Are NAND Gate Pinouts a Standard?

I have this really old NAND gate that I need to replace. As you will see, the datasheet is worthless and it is the only one that I can find. This is my first experience using a NAND gate (I ...
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1answer
108 views

How do I debug red signals in ModelSIM?

I have to design a state machine using only NAND gates for the combinatorial part and D flip flops for the sequential logic. Everything should run at a clock of 1ghz/53. Now before you assault me ...
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1answer
22 views

how to simulate 4 bit ring counter using max+plus II

I'm newbie with max+plus II and digital modelling world just want to simulate a simple ring counter https://www.dropbox.com/s/47tlv3g7o9zi8gb/all.jpg the ring counter's initial value must set to 1 ...
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4answers
112 views

What are logic gates?

So from what I understand transistors are one of the most important electronic elements for computers because of TTL (Transistors-Transistors Logic). Is this true? If so, how exactly does this work? ...
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0answers
73 views

Digital Latch Circuit with Unknown Outputs

Introduction I am a student currently enrolled in a digital course course. I'm actually an analog kind of individual so I (like most other analog people) have a hard time understanding logic. ...
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3answers
155 views

What is the best transistor for a large RTL (resistor transistor logic) project?

I've been reading up on older computers like the PDP-1 and TX-0. I'm fascinated with them and love the idea of making a CPU of my own using discrete resistors and transistors. Keep in mind, this is ...
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2answers
42 views

Expression and gate not gate output

The expression I came up with this circuit is A'B + A'CD + C, would the output change to AB' + AC'D' + C' since it is inverted? I'm assuming the D input compliments and cancels out? What would the ...
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2answers
47 views

Understanding circuit : Output of a CD4017 with 1N4148 diode and RC circuit

I'm reading a circuit on a magazine (look at circuit below) and i don't understand , why the author put a 1N4148 diode and a RC circuit at the output of CD4017 , what is the operations of the RC ...
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1answer
27 views

Multi-input AND gates from 2-input AND gates

To realize a 3-input AND gate from 2-input AND gates, we need 2 such 2-input AND gates. Assuming we have infinite supply of 2-input AND gates, can we obtain a general formula for the number of 2-input ...
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2answers
108 views

An exercise on decoders

I have the following exercise: Design a circuit that takes a 2 bit binary and makes it x^3 (x cubed), using a decoder of your choice. I thought to do it with a ...
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1answer
69 views

Differential signal processing and generation

I am trying to interface to a Mitsubishi central aircon unit. Based upon the manual, the internal units communicate over a differential bus (I hope is TDM). I have a screenshot of the signal: How ...
1
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1answer
31 views

Real Time Data Capture System

I would like to build a system which could capture an analogue waveform data in real time. For the basic data acquisition system I can use an ADC to digitise an analogue waveform and store this in a ...
3
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1answer
76 views

Show numbers on LEDs

I'm a beginner in EE, so maybe the following question seems obvious to you. I have to design a circuit that get a number from 0 to 9 via a decimal keyboard, and then show the corresponding number on a ...
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2answers
1k views

Karnaugh Maps - What is the purpose of a “don't care” condition?

I've got a problem and was stuck for whole day.. I'm designing an octal to 7 segment common cathode decoder which only octal digits 2 to 7 are applied to the inputs of the decoder so combination for ...
2
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2answers
60 views

Dynamic Logic - Transistor Sizing

If we have a circuit in dynamic logic: What should the size of the charge transistors (Qe and Qp) be? I know that increasing the size improves the speed but also increases the dissipation, and that ...
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1answer
71 views

Arduino PWM pin vs digital pin PWM simulation

Do I understand it correctly from this thread, Why do some pins have `~` signs next to their numbers?, that the PWM pins generate a square wave signal independently from what the code uploaded to the ...
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3answers
61 views

How should a SPDT switch be wired for a digital input?

I want to connect a switch to a digital input on a logic board and make it so that the input goes high when the switch is pressed. I'll be using a SPDT switch: Should I connect the digital input to ...
2
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2answers
151 views

Counter is missing an output signal

I used a 4040 counter to count the pulses from an encoder. I then connected two counter output signals to an AND gate, and after that one way is go to reset 4040 counter. The issue is that when I ...
3
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2answers
325 views

How do radio stations broadcast information?

I have noticed that modern FM radio stations broadcast simple text information about them. While this does not affect the analog sound, it can be decoded by most modern FM receivers, including my ...
0
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3answers
118 views

How does VHDL handle bitwise operations?

I'm having a problem in some VHDL code I'm writing. I want to drive a signal with two other signals AND'd together like this: mysignal <= "010" and '1'; The ...
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2answers
57 views

Reducing the Number of Logic Gates by Gate Sharing

Truth table : Circuit : This circuit is created with K-map so it should have been simplified. Is it possible to reduce the number of logic gates by gate sharing? Are there any rule guiding me ...
5
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4answers
313 views

Will the schematic I created for my project work?

Edit: I made it and it works like a charm :D . Only had to connect the switch -ve to the -ve lane and the switch +ve to the +ve lane (not shown in schematic!!) and the circuit works like a chram. I ...
1
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5answers
152 views

How electrical signals converted into Digital (binary 1 0)

I already ask this question in yahoo and in Microsoft........they say that : did I mean to say how to convert analog signals to digital signals.....and they suggest me the theory of AD converter So, ...
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2answers
49 views

Implementation of Any Combinational Logic Circuit with a Decoder and some OR Gates

It is said that a decoder with n input has 2n outputs corresponding to the 2n minterms of the n input variables. An n-to-2n decoder and m OR gates can, therefore, implement any combinational logic ...
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3answers
144 views

Noobie at IC, need help with basic circuit that isn't returning correct values

Okay, first of, I'm a complete newbie at ICs and circuits and I'm doing this for a school project. I request answers to be in laymans terms and not proper, complicated terms. For my first ...