Questions tagged [current]

Flow of electric charge - typically movement of charge carriers, such as electrons. Measured in amperes (A).

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Howland current source for negative currents

I am currently in the process of utilizing the design of Howland in order to derive a source that is able to provide an \$I_{out}\$ between \$0A\$ and \$30A\$ at the output load \$R_L\$. As you can ...
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How to connect 16 gauge wire to DRV8825?

I need to connect 16 gauge wire to one of the pins of my DRV8825 motor driver. I know DuPont cables are not going to work because they typically max out at 5 amps. What else can I use? Also, is it ...
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Calibrating the current (uA) of a TI by using a 34465A DMM as a std and a suitable load

When calibrating a test instrument (TI) on its current generation using the DMM 34465A as the standard and a suitable load in series, I think the uncertainty budget should not include the accuracy and ...
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Crystals - Works on the principle of piezoelectricity or inverse piezoelectricity

I've done google search on the working principle of crystals and piezoelectricity. Nothing explains the actual principle. Is it piezoelectricity or inverse piezoelectricity? From what I've understood, ...
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How is it possible for a 12000 mAh battery pack to power a DC motor that requires 70 amps of current?

I have a DC motor: DC Motor Link And a battery: Battery Link The motor says it requires a continuous ~79 amps of current. The battery says it gives 12 amp hours per charge. I don't understand how it ...
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Current sensing using transimpedance amplifier

I am looking for a way to create a Transimpedance Amplifier like below (to convert current to voltage) The problem now is how to add the current source? The current I want is the one read from ...
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Crystal oscillator - Gain

I was reading more about the crystal oscillators and had this question in mind. During the initial start up, the gain of the oscillator should be large and later on, the gain should be greater or ...
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Why can't we use crystal oscillators in series mode itself instead of parallel mode

I'm reading about the crystals and found that the crystal can be operated in series mode resonance as well as parallel mode resonance. In the case of series mode resonance, no external load capacitors ...
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Inductance depends on the number of turns in a solenoid. Is this the case with reluctance as well?

The total flux (\$\Phi\$) through an solenoidal inductor of length \$l\$ and \$N\$ turns is proportional to the current through the inductor and the inductance \$L\$ of the inductor according to $$\...
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When do we add a resistor between the inverting and non-inverting terminal of an op-amp

simulate this circuit – Schematic created using CircuitLab In the above image, let's assume for namesake that the op-amp is powered and there are inputs at both the terminals. My question is , ...
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RC 90 deg phase shift

What does 90 deg phase shift actually mean? Like, consider this below RC circuit. simulate this circuit – Schematic created using CircuitLab From what I understand, when I apply a sine wave at ...
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Should the load capacitance value connected to the crystal be the same

I've seen many app notes and calculations that in the above circuit, the value of C1 and C2 are the same. I haven't seen in many places where the values of C1 and C2 can be different. Can someone tell ...
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Resistor across crystal for biasing the internal op-amp [duplicate]

I've seen this below resistor across the terminal of the internal op-amp and also connected to the crystal. I've read that this resistor is required to provide the biasing for the circuit so that the ...
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Output load current less - DCDC Converter [closed]

I'm using this Boost converter. 3.6V to 12V with a load current 300mA. 10uH is the inductor used. But I am only able to get a maximum load current of 120mA. What might be the reason?
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Switching frequency data not available

Why do some dc-dc buck or boost converters do not have the switching frequency value in their datasheet? For example: Link does not have switching frequency ? Is it possible to get power dissipation ...
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Tail tagging feature in Ethernet and this product

I'm going through this KSZ8795 IC. In the description of the product, it is mentioned as Gigabit Uplink. But in the product features on page 1, it is mentioned that all PHY ports supports 10/100 Mbps ...
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Bob Smith Termination - Where should we use it? [duplicate]

What is a Bob-smith termination and why do we use it? I've seen it being using in Ethernet RJ-45 connectors where it is terminated to Chassis ground? Can someone tell me how this type of termination ...
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High value resistor connected across the crystal (between the inverting and non-inverting terminals of an op-amp) [duplicate]

I've often observed a high value resistor connected across the crystal (between the inverting and non-inverting terminals of an op-amp). Can someone tell me why is that? What's the purpose? Reference ...
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Current source controlled via PWM

Trying to simulate a sensor that acts as a current source. This sensor generates 2 current values: 10mA (low signal) 20mA (high signal) I will be using an STM32F4 micro - PWM output pin to try to ...
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PWM Controlled Current Source to drive 24V Proportional Solenoid Valve using Arduino

I would like to implement a PWM controlled current source to drive 24V proportional solenoid valve using Arduino. What I need are the following: Input will be 5V PWM with 5000Hz frequency, duty cycle ...
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Clock out drive strength - Current

In the datasheet of this IC, what is the benefit or purpose of having 12mA and 16mA drive strength for the clock output pins? What is the purpose of having 2 drive strength values for the clock? Is it ...
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How to control current to charge batteries?

I have a project that is powered with a 1s battery pack (multiple 18650 in parallel). I use following module to protect against overcharge/overdischarge : https://aliexpress.com/item/32982853134.html ...
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Base resistor too low problematic?

I have recently designed and ordered some PCBs which can combine a horizontal and a vertical video sync signal into one composite sync signal (all are TTL signals). This is done using a BJT circuit ...
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Should I use one thick wire or many thin wires in a step-up high frequency transformer to reduce resistance and impedance?

I am planning to make a step up high frequency (hundreds of kHz) transformer. I want to reduce the resistance and impedance in the secondary. Should I use one thick wire in the secondary, or should I ...
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Peak current of inrush limiting inductor?

I have this tricky question and I can't wrap my head around it. There is this inductor to limit the inrush current that will be charging up a capacitor. I'm questioning the design of it, but I don't ...
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Are smartphone cells actually charged with 9V using QC and other techniques or does the smartphone always step down the voltage?

I'm having this disagreement with a good friend of mine regarding charging voltage of the cells inside modern smartphones when quick charge, USB PPS and other techniques are used. Let's take as an ...
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Off-grid computing

I am designing the electrical system for a school bus to tiny home conversion (skoolie, by jargon.) The current iteration is entirely solar powered, somewhere around 2640 W in panels, and likely 1000 ...
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Current transformer wire issues

I would greatly appreciate some advice regarding twisted pair conductors for a current transformer. So, according to the manufacturer, whose equipment I am installing, I need to connect 10 AWG, ...
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What prevents old (low current) USB cables from catching fire if used to Quick Charge modern devices (at high-current)?

Let's say I have A very old Micro-USB cable. It's USB 2.0 and rated for a max current of 5V, 0.5A (2.5W). A modern, power-thirsty, quick-charging tablet that charges over micro-USB at a max of 100W. ...
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Graphing modes of BJT

Suppose we have this Ic vs Vce graph of a BJT transistor I have been taught this graph is applicable for this BJT transistor configuration. simulate this circuit – Schematic created using ...
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Calculating the reading on ammeter \$A_1\$: why am I incorrect?

I have the following circuit: The voltmeter \$V_1\$ measures the voltage drop across the \$9.00 \ \Omega\$ resistor and has a reading of \$4.50 \ \text{V}\$. I am trying to calculate the reading on ...
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What's the difference between Maximum working current and upper limit of instantaneous current? [closed]

I am seeking to protect a Mabuchi RS-380-SH4535 motor + battery system using a BMS. The battery is a single cell 18650 LiIon. The motor has a stall current of 15 A at maximum battery voltage. My ...
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2 votes
3 answers
105 views

Vending machine motor: simple DC motor with microswitch, one revolution

Long story short, I'm currently trying to understand and control a DC motor with connected microswitch, which gives back one-revolution feedback (don't know how). I tried connecting INA219 current ...
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How do I compute the power consumption of an audio amplifier?

I intend to use this audio amplifier in my project : PAM8019 It has two analog inputs : left channel and right channel. It has two analog ouputs, which are the amplified inputs. Let's say I follow the ...
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Normal Switch and LAN9353

I am reading about the different types of LAN Switches. And I came across the LAN9353 device - Link I want to understand the difference between a normal Gigabit Ethernet 3 port switch and this LAN9353 ...
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External Interrupt Peripheral Microcontroller

I'm using this ATSAME53N20A-AU microcontroller - Link I'd like to know what does the EIC and EXTINT peripherals would do? So, I went through the Appnotes - EXTINT and EIC I just want to know whether ...
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6 votes
3 answers
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How can a reed switch be used for high current applications?

I am planning to use a reed switch as a power switch in my underwater robotics project. The switch will be placed between the LiPo battery (16.8V, 20.8Ah) and the load. The load mainly consists of two ...
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4 votes
2 answers
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How to stop current from passing through a transistor?

I have this circuit. When sw1 is open the LED should be off. The thing is, some current passes through the transistor even though it's off making the LED light up dimly. Is there a way to fix this, ...
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1 answer
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What are relationship between cable properties and electrical properties?

I was prototyping esp32-cam (microcontroller aka MCU) on breadboard, I saw brownout error message on serial monitor everytime I initialize WiFi then it keeps restarting. After I google for 24 hours ...
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Current in a induction dc motor [closed]

SO I am building an induction dc motor and using a battery that supplies 12V and 7.0Ah. The wire I am using is a 0.8mm enamel copper wire and I am trying to find how much current was drawn from the ...
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If two devices both require 12V 2A power can I use a 12V 4A power supply to power them both?

The question title says it all really: I have two devices that both require a 12V 2A power supply, so I'm assuming that I can I just use a single 12V 4A power supply to power them both? I'm also ...
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1 answer
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I don't get the formula RIN = beta * RE

There is a formula in Malvino's book (page 210 of the 6th edition) which states that the input base resistance of a transistor is beta times the emitter resistance. To quote: "When seen from the ...
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Pin Buffer Types

I'm going through the datasheet of this PHY Transceiver LAN8742A On table 2.2, it is mentioned as buffer types. I see a row called as O12, which stands for Output 12mA sink or Output 12mA source. My ...
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Modeling three phase load for EV charger

When designing a power system to supply EV charging stations, are the stations modeled as delta loads or wye loads? Slightly off topic but is it standard practice to assume that three phase loads are ...
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3 answers
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Resistance measured individually vs measured on PCB

I always wanted to ask this question. Suppose I have a 1kohm resistor. I measure its resistance by connection a multimeter to both of its terminals (when it is not connected to any part of a circuit.) ...
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Is it possible to increase the current of an Arduino Nano 3V3 pin without altering the voltage?

I am trying to use an ESP8266 with an Arduino Nano but I see that the NANO can not enough current for supplying ESP8266 from 3V3 pin. I think it is limited from the faactory. If I use the 3V3 pin RX ...
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2 votes
4 answers
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How can I best reduce the current drawn by a PCB heatbed?

I have a noob question about fairly basic circuit design (I think). I am building an incubator for making Tempeh at home, and want to use an old PCB heatbed I have lying around as the heating element. ...
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2 votes
1 answer
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Same part devices supporting different temperature ranges

I just had this question. We often come across microcontrollers having the same internal peripherals and supporting the same functions but supporting different temperature ranges. Can you tell me how ...
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Why is the input current for a forward converter negative for a short time? [closed]

We have made some lab excercises with a forward converter and I was wondering why the input current of a forward converter is negative for a short time. Screenshot of oscilloscope can be seen below, ...
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Is voltage important for calculating PCB trace width? If not, why?

As per the IPC 2221A the formula for calculating PCB trace width follow the process given below; First, the area is calculated: Area[mils²] = (Current[Amps]/(k*(Temp_Rise[°C])b))^(1/c) Then, the width ...
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