Questions tagged [current]

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

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Should a USB wall charger protects its two USB lines against fluctuation in the other line? [closed]

I have a USB wall charger with a USB-A and a USB-C outlets. I have two identical USB-A LED lamps, and a USB-C Android pixel 8 phone. The desired setup is to plug the charger next to my bed, power one ...
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Power supply A output [duplicate]

I need to replace the power supply for a printer as the one it came with fails during high density prints. The input on it is 110 – 240V ~ 1A 50 / 60Hz and the output is 24V ⎓ 2A. After looking at the ...
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How to buffer tri-state GPIO pin for higher source/sink current?

Edit: I am not looking for a circuit to drive LEDs. I am looking for a generic solution to buffer a tri-state GPIO. My mention below of the bi-color LEDs is only to explain why I need to maintain tri-...
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$I_{on}$ and $I_{off}$ of MOSFET

I have a question from test ( translation from my language to English ): We want to create MOSFET with $\frac{I_{on}}{I_{off}}=10^4$. We also know that $s=80m[V/dec]$, what is the minimum ...
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What should I expect and how can I simulate two PIN photodiodes in series?

I am trying to modulate the current through a PIN diode using another PIN diode. I want to do fast modulation, so I would like both of them to be in reverse bias. If I use the configuration shown in ...
46 views

Induced EMF in a stationary coil

Suppose a there is a coil which hasvelocity=0 and we can say it does not experience any force due to themagnetic field. There is no role of induced EMF in any case. If we place a stationary coil and ...
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What is the purpose of R1, D1 in this gate driver? How they can control the turn on/off time?

I'm reading the datasheet for the ZXGD3004E6 gate driver. I don't understand why R1 and D1 are there.
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Is it possible for a fuse to blow at extremely low temperatures?

From what I understand, when a circuit is overloaded, the fuse heats up and eventually blows. This means that the fuse blowing is typically caused by high temperatures resulting from the overload. Is ...
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100 views

Can an LED connected to a USB port draw more current than its own requirement? [closed]

I did an experiment with a LED. I powered it with a 9V battery(the common rectangular shaped battery). Do not know its exact current rating but on the internet it is 50mA. The LED was working fine. ...
1 vote
86 views

Inrush Current Limiter

I designed a Inrush Current Limiter circuit reference from youtube .The circuit works some way I want to know is this works really like this. I done the simulation LTspice I want know is this ...
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Why a driver for LED bulb may not output enough current?

The driver shown in the pictures below, is for a little 7-watt LED bulb with 9 2835 SMD LEDs. The IC used in the driver is MT7828C whose datasheet and “Typical Application Circuit” you can see here. ...
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566 views

Produce -5 V with 250 mA max current limitation

How to produce -5 V with 250 mA max current limitation from a PSU with 12 V, -12 V and 5 V? I could use a 7905 to produce -5 V, but then I can not find an IC of type Current-Limiting Power ...
128 views

Why does electric current not disobey Heisenberg's uncertainty principle?

So, the definition of current, or the magnitude of current, that I have found is that it's the rate at which the electrons flow through a cross-section of a wire. But that means knowing exactly where ...
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Why does characteristic equation and DC model equation for drain current in JFETs do not agree?

I am reading Semiconductor Devices — Theory and Application (Fiore) about JFETs in chapter 10 and there are two drain current equations shown that do not agree with each other. The first equation is ...
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1 vote
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MCP39F521, a Triac (T610), Load on Neutral & Measuring V and I

I'm trying to build a AC “power bar” with metering per “outlet”. The 2 most interesting chips I found are the Microchip MCP39F521 and the Allegro ACS37800. Due to costs, I've chosen the former. The ...
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Ampacity rating of a wire

Is the ampacity rating of a wire only pertains to the current rating? For example, if I have a 14awg wire and has a load of 10VDC/30A, is this the same as 100VDC/30A load? I understand that they will ...
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How does this LM317 current boost circuit work? [closed]

Can someone please explain how this circuit works, as well as explaining the roles of each component in the circuit? What is the effect of the 500ohm resistor and the resistor on the right side of ...
102 views

1.5 mA Current Source Design Recommendation

I measure temperature with the PT100 temperature sensor. With the circuit below, I obtain a constant DC current of 1.5 mA. I use tempref value as 3 volts and R2 resistor value as 2k. Although this ...
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1 vote
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How does a digital multimeter measure?

I have a pulsating signal (always positive) with a frequency of 50 Hz and a true RMS multimeter. Should I measure the voltage with the multimeter on DC or AC? What´s the multimeter doing in each case?...
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High current voltage controlled current source MOSFET selection

I am working on adjustable voltage controlled current source (2 to 3 A) for my project. I tried different NMOS for the projects, but they all burned. In my application, the resistance of my load is ...
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What if negative is less conductive than positive wire in DC circuit? [closed]

In almost all trucks, the chassis and battery's negative are shorted. Say we are to install a vehicle tracker that operates on 12v DC. The positive sides are connected via a copper wire but the ...
2k views

How can DC charge a capacitor?

I read that a capacitor shows infinite resistance towards DC. While solving questions we use DC to charge the capacitor and use a constant potential difference and current. This contradicts that DC ...
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Why dos my 12V adaptor give electric shock even when switched off? [closed]

Even when the mains supply is switched off but plugged in, my 12V adaptor gives electric shock, like small currents. Why? This is my adaptor And this is where I feel the shock
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Is the coulomb unit a constant or does it depend on the wire?

I'm completely new to electronics, and I'm a bit lost on the definition of a coulomb. I tried to find a decent definition, but they all seem to equate to something like: The coulomb (symbol: C) is ...
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Can someone explain the working principle of this diagram?

In my opinion, during daytime because our battery is only 3V, the solar panel produces more voltage and because of voltage difference, voltage flows from solar panel to battery and there is no ...
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Wires branching in parallel with lipo battery and how would the current behave

If I have a 45C, 1.8Ah lipo battery (81A?) that I want to connect to a constant current driver that can only take up to 10A, would it be possible to use 8 wire branches (with no components) in ...
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I need to prevent a small quantity of water from freezing using a solid state controller circuit

I am currently using a 10W resistive heater element powered by a 5V 2A DC power supply, which works fine, but is unsatisfactory since it's either on (plugged in) or off (unplugged) making it subject ...
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LEDs Progressively dimming even for light intermittent usage

We have been developing an LED array board with a PCA9959HNMP constant current driver, which controls SM0603UV-405 LEDs from Bivar. The UV LED's absolute max forward current is 25 mA, I have used a 2....
1 vote
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Transistor switching speed

I want to be able to identify the speed of a transistor in terms of switching. Most datasheets don't indicate that but I found this transistor from ST-Electronics. Is it the maximum switching ...
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Can a voltage higher than LED maximum be used when using constant-current LED driver?

I am planning to use these components: TLC59283 CREE J Series 5630 LEDs Specifically, I want to create a setup like Figure 9-1 on pg. 22 of the TLC59283 datasheet. Currently, I am trying to choose a ...
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How to know what size diode to use for inductive spiking?

I am making a simple Zener flyback circuit for an inductor. What current rating should the diodes be sized for? Could I use a 1 watt Zener diode because the voltage spike only lasts a few microseconds,...
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Is a capacitor a memoryless system?

According to my textbook, A system is said to be memoryless if its output for each value of the independent variable at a given time is dependent on the input at only that same time. It also gives ...
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Current varies with constant firing time in an SCR

Please bear with me as I am not a power electronics guy. I have a circuit in a battery charger that triggers SCRs, attached here. I am generating the fire pulse from a microcontroller at a constant ...
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Why, when conductors are connected in series, their current strength is equal?

Why, when conductors are connected in series, their current strength is equal, because the resistivity of the conductors can be different?
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Three phase rectifier output current

I´m designing a three phase power transformer, and i´m having troubles with the choosing the current value. After the transformer, goes through a three phase bridge rectifier ( full wave and not ...
1 vote
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Distribute power from one battery to multiple devices

I have a battery, Li-po 3300mAh 22.2V 60C. Then, I have a system (main system, so to speak) which consist of STM32MP1 MPU (operating voltage [1.71, 3.6], typ. 3.3), STA8135GA GNSS IC (operating ...
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1 vote
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Should I replace my stepper driver since my motor is acting up?

I've been using a Pancake Bipolar Stepper Motor for a project and STSPIN220 as the driver, but I've been randomly having a lot of current issues causing my motor to jitter. My project has been running ...
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Why is a push-pull transistor configuration asymmetric?

Looking at the circuit below: How do I analyze it? Specifically, why is the output able to go nearly all the way to +12 V but not beneath 0 V? I'd expect that when V(sig) < 0, since current flows ...
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Voltage and current on two identical TVS diodes in parallel during a voltage spike

Suppose I have two identical unidirectional TVS diodes (A and B) connected in parallel to a voltage source and suddenly a voltage spike occurs (spike voltage > voltage clamp of the TVS diode specs ...
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Is my stepper motor driver causing me current issues or is it me?

I've been using a Pancake Bipolar Stepper Motor for a project and STSPIN220 as the driver, but I've been randomly having a lot of current issues causing my motor to jitter. My project has been running ...
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How to measure battery voltage during charging?

I have a slight confusion regarding the battery. Suppose I have to charge a battery of initially 12V to 14.2V (full charge). My charger has open circuit voltage of 15V. When I connect it what voltage ...
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How much current will a BJT transistor draw through its base?

If a BJT transistor has a voltage Vb at its base, its nominal emitter voltage Ve will be Ve = Vb - 0.7. If we know Re, we know the current through the emitter Ie = (Vb - 0.7)/Re. If beta is high, ...
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Does negative current mean the flow of negative charges? If so where do the positive charges from I_1 and I_3 go after reaching the blue node on the image below? I do not understand how the positive ...
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Powering on a laser diode that exceeds PSU max current

I have a laser diode that I want to test (just seeing if it turns on). However, the threshold current is past the 10A that my bench power supply can supply, hence I can't generate any light. How can I ...
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Why is the power conserved in a phone charger?

Most phone chargers draw 220V 50mA (for example) from the socket to inversely proportional draw 5V and 2.2A (in its converter) to charge the phone at 2.2 A because power is conserved. Why is power ...
1 vote
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Buck-Boost fault mode on startup and gradual current decrease

I am using the TPS92692 in buck-boost mode with an analog signal to set Iadj and PWM. When I start the circuit, it consistently goes into fault mode and the fault pin is periodically set low. However, ...
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1 vote
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Do we need MPPT in grid synchronization and string inverters? [closed]

I have two questions regarding the MPPT grid synchronization. I have seen that it takes a few minutes for the inverter to get synchronized with the grid. I want to ask that does the inverter first ...
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https://www.youtube.com/watch?v=G8JgS-STozA&t=537s First, I apologize this video is in a different language, but I'll point out what is relevant. So, in this video. There is a man saying that his ...
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