Questions tagged [input]

Something put into a system or expended in its operation to achieve output or a result

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BJT Input AC Signal Amplitude

This question is referring to npn BJT CE: If we look at base voltage vs. collector current plot we can see that at approximately 0.7V on base to emitter junction, the BJT starts rapidly conducting. ...
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9 votes
9 answers
6k views

12V input on microcontroller pin

I'm trying to count pulses/sec. on a microcontroller pin in the ~5 to 100Hz range. The µC can operate at 5V input, so I have to get the voltage level down safely. A simple resistor comes to mind, yet ...
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  • 621
8 votes
2 answers
2k views

What is the use for non-inverting input resistance in a negative feedback opamp?

Here in the Figure R5=50K. This resistor value is not in the equations to obtain output voltage, and in many tutorials non-inverting input is directly grounded without a resistor. What might be the ...
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6 votes
7 answers
13k views

Multiplexing Inputs on a microcontroller

I have a 4 way DIL switch that I use to provide input to a microcontroller, and I need to free up a port to use for something else. Is there a way to multiplex 4 inputs into 3 microcontroller ports? ...
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  • 5,758
12 votes
6 answers
19k views

Input voltage range of opamps

I understand that, for an ideal opamp, Vo is bounded by Vee and Vcc (i.e.; Vee < Vo < Vcc). But, what about the input voltage range? What is the allowed input voltage range in which opamp works ...
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7 votes
3 answers
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PIC - How to skirt around low maximum ADC input impedance?

Reading a 9V battery on a PIC is nothing new. The most simple and straightforward way is with a voltage divider. I'd like to keep the divider resistances cranked up into the hundreds of kohms so I'm ...
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0 votes
1 answer
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Controlling a single phase AC fan with a 0-10V DC input

I have a fan motor which is a permanent split phase single phase capacitor motor: http://uk.rs-online.com/web/p/axial-fans/2781543/ I currently control this fan's speed with the following controller:...
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4 answers
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Understading negative feedback [duplicate]

There is a question here about something similar, but it's asking about the internals of an op-amp. I'm having trouble understanding the function and use despite several hours of YouTube tutorials. ...
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2 votes
2 answers
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5v output to 3.3v?

I have a microcontroller and a Raspberry Pi, both running off of the same 5v supply, in parallel. The microcontroller has 4 5v output pins and the other is a Raspberry Pi, that can only accept inputs ...
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12 votes
4 answers
3k views

Is this clamping voltage divider for a high-impedance input a good, robust design?

I have an AC input as follows: Can range from ±10V to at least ±500V continuously. Runs from roughly 1 Hz to 1 kHz. Needs > 100 kΩ of impedance on it, otherwise its amplitude changes. May ...
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10 votes
1 answer
6k views

How is this 5-24V input circuit working?

Since I require some kind of wide range input (going to a microcontroller) for a new project, I looked through some designs that are already in use (or were considered at some point) for other ...
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9 votes
1 answer
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How to implement a "rotary switch" like in audio equipment?

for my current project I'm planning to use an input "device" like this in the photo (don't know its real name): It is used in a lot of musical instruments and it is like a potentiometer that can be ...
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  • 317
9 votes
1 answer
1k views

What's mean these microcontroller pin input/output modes?

I bought an stm32f103ret6. When I saw the reference manual, I saw that it has several I/O modes. For input: floating, pull-up, pull-down For output: analog, open-drain, push-pull I have already ...
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  • 381
6 votes
4 answers
28k views

3 input XNOR gate operation

For 3 input XOR gate and XNOR gate, by solving the equations I got the result as in the picture. So according to the solution the outputs of the 3 input XOR and XNOR gates are same. This solution ...
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  • 133
2 votes
3 answers
6k views

Digital Input Clamp Circuit Protection

To be able to connect some peripheral to digital input, I'm designing the circuit protection to avoid any possible failure due to over/under-voltage issue. So, I will add a clamp protection circuit. ...
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  • 357
1 vote
5 answers
10k views

Can an opto-isolated input be analog?

Title says it all: can an opto-isolated input be analog or are they intrinsically digital? Why: I am looking to purchase a relay control board and am deciding between a few options. Here is my ...
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0 votes
1 answer
4k views

MCU Input Protection

I am working on a simple protection circuit for an I/O pin on an MCU. The device will be 3v battery powered. The MCU's I/O pin has a voltage tolerance of (GND - .6V) to (Vdd + .6V). Pull-to-ground ...
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  • 159
2 votes
2 answers
296 views

Is there a way to measure the Phase Shift between the input and the output voltages related by the equation: \$V_o = V_i(a+jb).\$? [closed]

Say \$V_i\$ is an input voltage, and the output voltage is given by \$V_o = V_i(a+jb).\$ Is there a way to measure the Phase Shift between these input and output voltages?
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2 votes
1 answer
2k views

Vbe vs Ic characteristics of NPN transistor at different Vce in active region

Below is an NPN transistor characteristics for Vbe versus Ic at different Vcb or Vce: It seems like in the active region, Vbe vs Ic curves gets steeper with an increasing Vce. The following ...
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1 vote
3 answers
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What are the mechanisms at work in a pull-up or pull-down resistor circuits with a push-buttons and a GPIO?

I have a question regarding the GPIO (from a Arduino board for example). How does it work exactly when you use it as an input pin? What are the mechanisms at work when you use it in a pull-up and pull-...
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26 votes
3 answers
36k views

How do I extend the number of analog (input) pins available to me?

I already know how to extend the number of digital pins on an Arduino using a multiplexer. I want to increase the number of analog input channels that I have. One solution is to add another Arduino ...
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  • 2,832
38 votes
8 answers
3k views

Add a passive hardware token using a 3.5mm jack

I have a box that I made for my niece, which allows her to exchange voice messages with me. It is powered by a Raspberry Pi and features two buttons, a LED, a microphone and a speaker. Now, for ...
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  • 603
7 votes
3 answers
15k views

What kind of diode to use with ADC inputs

I am looking for diodes to protect my ADC from over voltage conditions. From what I have researched so far, I know that I need schottky diodes hooked up from the input to the ground and the input to ...
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  • 1,970
12 votes
3 answers
3k views

Can unconnected inputs make an IC get warm?

I am using an ATF16V8 PLD for some simple glue logic. While testing it on a prototyping board, I noticed that it gets warm to the touch almost immediately. I checked that no outputs were short ...
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  • 399
6 votes
6 answers
4k views

Simplest possible I/O for Homebrew 8-bit CPU

I am working on designing an 8 bit cpu as a personal project for no real reason. I am using mostly 74HC series chips and am generally focusing on ease of programming over performance. I am using ...
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  • 2,044
15 votes
5 answers
17k views

Considerations when using internal pull-up/down resistors

I am working with STM32 micro-controllers. These micro-controllers have the option to set the input pin as pull up or pull down: Earlier I used to give external pull up or pull down resistor wherever ...
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  • 7,532
12 votes
3 answers
3k views

12 V input on 3.3 V GPIO, TVS pulled down or Schottky pull up?

I am building my own PLC that has to accept permanent inputs of up to 30 V DC into a STM32F with 3.3 V inputs. The switched input will have to work with 8-30 V, but 90% of the time the ...
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11 votes
4 answers
3k views

Where Does VDD+0.3V Input Limit Come From on IC chips?

There are a variety of integrated circuits that specify that their input voltage can span a fairly wide (absolute maximum) range, e.g. -0.3V to 6.0V (ref, pdf page 4), and then have a "Input Voltage ...
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7 votes
2 answers
6k views

How to trigger a transistor from iphone's audio output jack?

I want to trigger a transistor using iPhone's audio output jack. My goal is to turn off an LED(which is fed by an external +5V battery) by sending an audio signal from iphone's output jack. At the ...
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1 vote
1 answer
1k views

Wide voltage range input regulation (24V - 3.3V)

TL; DR: I need a circuit capable of handling input voltages from 24V to 3.3V (with a 10mA/5mA maximum current) and delivering 3.3V to the microcontroller (ESP32) input. Recently, I've been working ...
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8 votes
3 answers
8k views

Arduino Analog Input example clarification

First of all I'm total nub in electronics. Recently I got an Arduino Nano. Now I'm trying to understand why there is no potentiometer nominal at http://arduino.cc/en/Tutorial/ReadAnalogVoltage ...
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  • 183
3 votes
3 answers
9k views

How to make clamping circuit to clamp exactly at 3.3 volts

I am building a circuit that attenuates the signal and sends it to 3.3V ADC, so I need to limit max voltage to 3.3V. After testing out some circuits for clamping the voltage(various schottky or zener ...
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2 votes
1 answer
715 views

Can you use a stepper motor as input?

I'm not too versed in EE so I apologize for my duncitude - My thought is that you can precisely control a stepper motor, but can you inversely get precise readings out of a stepper motor? For ...
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2 votes
2 answers
11k views

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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1 vote
2 answers
693 views

Several Questions About Analog Input

I am new in the automation industry, and now I am focusing on learning how to wire correctly analog inputs in detail, since last time I tried I damaged the module input because of wrong wiring. Here ...
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  • 225
0 votes
2 answers
89 views

Keyboard USB transform

I want to press a key on my keyboard, for example "a" and a device should take the scan code of the button I pressed and transform it to something else: e.g. "b" or the scan code ...
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0 votes
3 answers
652 views

Help to build a circuit to trigger event only after input signal changes from "1" to "0"

I'd like to build a kind of logic as shown in the picture ,but I can't do it and I really appreciate if someone can help on that. Basically what I'd like to achieve is that when the input signal ...
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9 votes
4 answers
3k views

Does there exist an IC that allows on-the-fly routing of signals?

Do there exist ICs with N input pins and N output pins which, either via EEPROM setting or via on-the-fly control by a microcontroller, allow one to route each of the N inputs to ANY of the N outputs? ...
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5 votes
3 answers
1k views

Measuring input current of opamp

I want to measure the current that goes into a noninverting opamp input. I've setup my experiment as follows: I can't measure the voltage drop across the 10M (R1) resistor directly since my DMM has ...
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4 votes
4 answers
3k views

Input impedance of an op Amp

I noticed that the input impedance of an op Amp is extremely high. Why is that so?
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3 votes
1 answer
1k views

Op Amp input protection

I was looking for an Op Amp input protection circuit and the most common I found looks like this. When the voltage at Input Signal goes above/below Op-Amp's supply ...
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  • 1,900
2 votes
3 answers
2k views

Bipolar Op Amp w/ Near Zero Offset?

My understanding is that if source resistance is low, a bipolar op amp has 10dB less noise than a JFET. I prefer the JFET op amps because the input offset is so low that you can eliminate coupling ...
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1 vote
1 answer
41 views

Input range for TPA311x

I'm reading through the datasheet of the TPA311x family. I'm looking for the input range for pins INPR and INPL but I cannot find this information. I see the absolute maximum ratings, but it's not ...
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1 vote
1 answer
317 views

Is 3.5VDC going to damage an stm32 analog input?

I have a pressure transmitter sensor that is supplied with 5VDC and provides 0.5-3.5VDC analog value within a pressure range of 0-4bar. The system that I'll be using the sensor within, will almost ...
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1 vote
2 answers
3k views

How can I interface with these 24 V signals?

I have a few 24V inputs to my micro controller from Limit switches. I have conditioned the signals as shown. Pulled down, de-bounced and level converted. I have some signals that are again 24V but ...
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1 vote
1 answer
908 views

Sallen Key topology input and output impedance

Ideal Operational amplifier Zi=(R1+R2)||Zc2 Zo=0 741 Operational amplifier Zi=(R1+R2)||Zc2 Zo=0 (at DC) For the input impedance when using a 741 I am not sure if I should consider the Fairchild ...
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  • 53
1 vote
1 answer
482 views

DC Op-Amp Output at an unexpected voltage?

For some reason Op-Amps are impossible for me. I'm experimenting with them a little bit. I have the following circuit... simulate this circuit – Schematic created using CircuitLab This is the ...
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  • 705
1 vote
2 answers
304 views

dsPIC 30F6012A will not read RD9, appears to be software problem

I'm using a dsPIC 30F6012A. I have two PCBs with this chip, both displaying the same symptoms, implying it's not one-off damage. RD9 is definitely being driven to five volts, confirmed with a ...
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1 vote
2 answers
1k views

Detect 220Vac signal on Microcontroller

I'm developing a module and the control switch may be at long distances. Considering I have the 127 or 220Vac input, I want to use that for switch signal. I believe is better, instead of making a ...
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1 vote
1 answer
575 views

How not to waste power with digital inputs?

I am trying to make simple gates with n-MOSFETS, yet I'm not sure how to actually do physical gate inputs correctly. At first, I tried this (a single-pole, single-throw switch from +5V to gate). ...
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