Questions tagged [input]

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

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38 votes
8 answers
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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 ...
Besi's user avatar
  • 727
26 votes
3 answers
37k 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 ...
Manishearth's user avatar
  • 2,902
15 votes
5 answers
22k 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 ...
Whiskeyjack's user avatar
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14 votes
4 answers
6k views

Why does most test equipment have 10 MΩ voltage input impedance?

I'm only speaking for equipment interesting in voltage measurements. Multimeters, oscilloscopes and conventional lock-in amplifiers seem to have mainly input impedances of 10 MΩ. I understand the need ...
BlackPenguin's user avatar
13 votes
2 answers
25k views

opto isolated arduino input

I want to protect a pin with an opto isolator to get an external signal from an electrical meter (35VDC max, 50mA max, 240ms pulse width). The purpose is to count the pulses. Do you have some ...
hotips's user avatar
  • 401
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 ...
NeonMan's user avatar
  • 399
12 votes
2 answers
12k views

PCB "Touch" Button

Is it possible to use a PCB pad as a button? I think of using it to switch on a curcuit that is only supposed to be enabled, when the user holds it in its hands. As inspiration, I used the pads that ...
mxcd's user avatar
  • 469
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 ...
Newbie Noob's user avatar
12 votes
6 answers
22k 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 ...
hkBattousai's user avatar
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 ...
JohnSpeeks's user avatar
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 ...
vicatcu's user avatar
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10 votes
1 answer
7k 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 ...
Rev's user avatar
  • 10.1k
10 votes
2 answers
102k views

What is a "dry contact input"?

I'm a PC software guy, a newbie to electronics. Recently, I've got a project in which I need to source for a DAQ that can provide dry contact inputs to an interfacing digital output controller. The ...
Joshua's user avatar
  • 235
9 votes
9 answers
8k 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 ...
Christian's user avatar
  • 621
9 votes
4 answers
4k 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? ...
boardbite's user avatar
  • 4,912
9 votes
1 answer
984 views

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 ...
3mpty's user avatar
  • 317
9 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 ...
user16307's user avatar
  • 12k
9 votes
1 answer
3k views

Should I use a resistor between an input pin of MCU/CPLD and VCC/GND?

Some times, I want my MCU or CPLD to input a static logic. So, I choose to tie it to VCC or GND. The problem is that should I put a resistor in series to limit the current? I just think by myself for ...
oilpig's user avatar
  • 853
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 ...
brian's user avatar
  • 391
8 votes
2 answers
952 views

What is the need for using active low inputs like EN' (read as "Enable bar") in digital electronic circuits? [duplicate]

Is there any special reason because of which active-low inputs are occasionally used instead of active-high inputs? Example: We have active-low inputs RD' (read as "READ bar") and WR' (read ...
Aditya's user avatar
  • 269
8 votes
3 answers
9k 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 ...
A B's user avatar
  • 183
8 votes
3 answers
6k views

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 ...
BB ON's user avatar
  • 2,304
8 votes
4 answers
2k views

Does a switch need to be debounced when opened?

Suppose that an input on a microcontroller has a pullup resistor to 5V and a switch to ground (normally open) connected to it. I know that a switch should be debounced (in my case, in software) when ...
Nate's user avatar
  • 4,526
8 votes
2 answers
896 views

How can I check input of USB?

I have following wire as shown below, one end has male USB connector and other end has four wires. I know, when connected to laptop, the RED one acts as voltage source and BLACK as ground. If I give 2 ...
Divanshu's user avatar
  • 195
7 votes
3 answers
16k 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 ...
Reid's user avatar
  • 2,040
7 votes
1 answer
695 views

Identify Vintage Power Cord for 1980s Organ [closed]

I Recently acquired a Technics SX-C600 organ but it needs a power cord. Does anyone know what type of power cord I should get for this? My understanding is that this is a rare organ.
JennaS's user avatar
  • 71
7 votes
1 answer
747 views

Input and Output pin voltage specs on a datasheet

I'm a bit confused about input pin voltage tolerances and output pin voltage values of ICs. I would think that datasheets for ICs that involve signal inputs/outputs would list two values: The ...
Thomas E's user avatar
  • 715
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 ...
user16307's user avatar
  • 12k
7 votes
2 answers
4k views

How to protect input against both ESD and reverse polarity?

I need to protect an external input on a device against both reverse polarity and ESD (IEC61000-4-2 +-8kV). The normal input is +5V dc at 100-200mA; the reversed input could be -5V and that should be ...
Alex I's user avatar
  • 3,401
6 votes
7 answers
14k 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? ...
BG100's user avatar
  • 5,808
6 votes
3 answers
2k views

How CRT allows use of ligh-guns or pens etc?

While reading about CRT on Wikipedia, an information (CRT Allows the use of light guns/pens; https://en.wikipedia.org/wiki/Cathode_ray_tube#Advantages_and_disadvantages) suddenly triggered a a vast ...
Always Confused's user avatar
6 votes
4 answers
38k 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 ...
turtle's user avatar
  • 133
6 votes
4 answers
3k views

How does a logic gate behave with an input changing faster than its propagation delay?

I am attempting to create a simple logic circuit simulator. I am having a hard time figuring out how does a logic gate behave with an input changing faster than its propagation delay. When attempting ...
David Porizek's user avatar
6 votes
3 answers
3k views

How can we read two digital inputs simultaneously from ATxMega128?

I am new here.. I have two IR sensors that give digital output (0 when there is something in front of it and 1 when there isn't). I am using a ATxMEGA128 to run motors using these sensors but I am ...
Ron's user avatar
  • 93
6 votes
2 answers
6k views

False Positives on Arduino Input

I've used analog and digital input for a multitude of applications with the Arduino Uno board. It has continuously given extremely non reliable readings, where the analog input is always fluctuating, ...
Mark Y.'s user avatar
  • 119
6 votes
2 answers
3k views

Is it OK to rely on an ADC's internal protection diodes?

Related to: ESD protection of ADC input. To protect an ADC input from out-of-spec voltages, including ESD, it is often recommended to use diodes connected to GND and Vcc. If I have a 1k series ...
Rocketmagnet's user avatar
  • 27.4k
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 ...
captncraig's user avatar
  • 2,054
6 votes
1 answer
7k views

Latched outputs on 8255A

I am studying about the 8255A PPI. In Mode 0 of it, it says that the outputs are latched and inputs are not latched. What exactly does it mean?
ayushgp's user avatar
  • 163
6 votes
4 answers
5k views

Why won't my arduino board read an analog pin correctly?

I'm working with an Arduino Uno board. I have a series of voltage dividing circuits off to the side of a breadboard to give me four different voltages. I'm connecting to my laptop. I am using the ...
Michelle's user avatar
6 votes
1 answer
226 views

Getting SPDT behavior (with zero quiescent current) from an SPST switch

If you've got an SPDT switch, it's pretty straightforward to use it as a front panel input to some CMOS logic. Even with simple debouncing (no hysteresis, which is acceptable for my purposes), it ...
Nicholas's user avatar
  • 381
5 votes
5 answers
30k views

Arduino Mega 0 - 10V analog input?

Is it possible to configure the Arduino to give me 0-10V analog input? I realize that I can use a voltage divider. I was just wondering if I can use a larger range for the analog input.
Kousha's user avatar
  • 151
5 votes
2 answers
2k views

Diode Clamp failing with LDO Circuit

I'm back with yet another mystery. Summary question: Why would an input to a voltage clamped circuit de-stabilize and or elevate that voltage clamp's upper rail? How do you properly clamp voltage ...
bathMarm0t's user avatar
5 votes
2 answers
671 views

Is there a way to find the transfer function from only your input and the steady state response?

I know that a transfer function has the general form of $$ G(S) = Y(S)/U(S) $$ where \$Y(S)\$ is the output and \$U(S)\$ is the input. However, if given the output \$u(t)\$ and the steady state ...
TheColonel's user avatar
5 votes
3 answers
16k views

What is meaning of active low input in combinational logic circuits?

I am currently doing self study on combinational logic circuits. I encountered few terms like active low output, active low input. I understood what active low output means (putting not gates at ...
user avatar
5 votes
2 answers
2k views

Clamping diodes or TVS

When should be clamping diodes preferred over one-directional TVS for input sanitation? Consider only digital inputs, not power lines. Clamping diodes seem to be recommended so I worry I might be ...
student's user avatar
  • 551
5 votes
1 answer
3k views

LD1117 vs LM1117

If I'm driving, say, a 500mA load, would you guys think that I could use these two parts more or less interchangeably? http://www.digikey.com/product-search/en?x=-1011&y=-71&lang=en&site=...
M D's user avatar
  • 51
5 votes
3 answers
4k views

Using Single Ended Output with Differential Input by Grounding one Input

I am making a frequency generator using the AD9833 (programmed from the PIC16F876). I wish to use a Programmable Gain Amplifier to adjust the signal level before being sent to a power amplifier (...
Tim M's user avatar
  • 2,008
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 ...
miceuz's user avatar
  • 5,561
5 votes
1 answer
810 views

ATtiny45 pin change interrupt PB5?

On the ATTiny45 data sheets it states that PB5 can be used as a digital IO pin and I want to use it to trigger a pin change interrupt, my only issue is that it is also the reset pin and the moment I ...
Gerharddc's user avatar
  • 285
5 votes
1 answer
305 views

Microcontroller output override another signal, protect uC when powered off

I have a digital signal from somewhere else and a microcontroller. The microctontroller can set it's output pins to be high, low, or high-Z. If the uC pin is high or low, I'd like the output to match ...
Jack B's user avatar
  • 12.2k

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