Questions tagged [input]

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

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26
votes
3answers
32k 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 ...
13
votes
2answers
19k 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 ...
12
votes
3answers
2k 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 ...
12
votes
3answers
2k 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 ...
12
votes
4answers
2k 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 ...
10
votes
5answers
6k 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 ...
10
votes
6answers
14k 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 ...
9
votes
2answers
5k 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 ...
9
votes
4answers
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? ...
9
votes
1answer
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 ...
8
votes
10answers
4k 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 ...
8
votes
1answer
839 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 ...
8
votes
3answers
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 ...
8
votes
4answers
1k 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 ...
8
votes
2answers
608 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 ...
8
votes
1answer
4k 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 ...
8
votes
1answer
958 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 ...
8
votes
2answers
85k 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 ...
7
votes
3answers
5k 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 ...
7
votes
1answer
500 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.
7
votes
1answer
331 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 ...
7
votes
2answers
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 ...
6
votes
7answers
11k 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? ...
6
votes
3answers
13k 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 ...
6
votes
3answers
786 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 ...
6
votes
2answers
834 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 ...
6
votes
3answers
2k 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 ...
6
votes
2answers
5k 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, ...
6
votes
2answers
2k 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 ...
6
votes
4answers
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 ...
5
votes
4answers
24k 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.
5
votes
4answers
2k 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 ...
5
votes
2answers
642 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 ...
5
votes
2answers
727 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 ...
5
votes
6answers
3k 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 ...
5
votes
1answer
2k 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=...
5
votes
3answers
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 ...
5
votes
1answer
682 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 ...
5
votes
2answers
362 views

What does it mean for an input impedance to be “differential”?

In a specs of a data acq. device the input impedance is shown as "20 MΩ differential". Does that mean the measured impedance in diff input case? If so how can I calculate the input impedance for ...
5
votes
2answers
262 views

Trouble chaining multiple low noise op amps

I want to experiment with receiving ELF signals. In particular 76Hz. The goal is to attach a coil of a few thousand turns of magnet wire, place it on the ground, and read the signal level. My ...
4
votes
4answers
2k views

Input impedance of an op Amp

I noticed that the input impedance of an op Amp is extremely high. Why is that so?
4
votes
4answers
1k views

Voltage across LED and source when LED is floating from one end

Refer to these pictures and can you explain why is there 3.335V coming across LED and the LED isn't even turning on. Also to note is that changing the resistor value does not change voltage at D2(A2) ...
4
votes
2answers
5k views

Configure a PIC pin for Input and Output

I am working on a project which uses a PIC24FJ64GA002 mcu. I am working on a bit-banged serial communication function that will use one wire to send data and then switch to receive mode to receive ...
4
votes
3answers
5k views

Using lots of slide potentiometer for computer control

I want to mount a bunch (say 16+) slide potentiometers in a long project box (or other housing that can sit on a desk) that I can use to interact with software on my computer, specifically lighting ...
4
votes
3answers
546 views

ESD protection for pH measurement electrode input

I want to puild a pH meter, which uses a normal glass electrode. Such an electrode behaves as a pH dependend voltage source (<+-500mV) with very high internal resistance (10MOhm - 1GOhm, depending ...
4
votes
3answers
3k 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 (...
4
votes
1answer
397 views

Associate std_logic_vector constant with input port VHDL-200X

I am trying to configure a chip over SPI interface using FPGA Spartan 6 Eval board. I just need to configure, I do not need to read the data from the chip, it will be done by another interface. ...
4
votes
2answers
220 views

Handling audio (from mic to headphones)

Right, I'm new to electronics, but this is what want to know: What do I need to take a mic input, and output it to some ear phones (standard jack, can be mono). I want to build a motorcycle intercom, ...
3
votes
4answers
15k 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 ...
3
votes
3answers
3k views

Why do we need bulky filters at the input stage of SMPS designs?

I usually see costly and large filters at the input stage of switch mode power supplies. Isn't the AC signal already filtered by the large capacitor (the 100\$\mu\$F one in this example) after the ...