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Questions tagged [current]

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

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59 views

Protecting back to back mosfets

I'm designing a high side back to back common source bidirectinal power switch made from n-mosfets. schema: Schematic attached. The questions: How can i protect driver from voltage spike from ...
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1answer
52 views

I dont know how to caculate initial current [duplicate]

simulate this circuit – Schematic created using CircuitLab I have a circuit of just a 240 ohm resistors and a 12 v battery. In the circuit the current after the resistors is 0.05. what is the ...
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62 views

Reducing Current?

Having a problem with my EV a converted Fiat 500. The conversion is made with part from companies that dont exist any more, so it is hard to get information about them. The car have two batterybanks ...
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0answers
32 views

Power SMD 5050 LED Strip from Orange Pi Zero 5V pin

I am trying to control a 5V 5050 LED strip with around 20 LEDs from an Orange Pi Zero. A lot of pages suggest to use an external power supply, but since my strip is 5V and only has around 20 LEDs, ...
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2answers
35 views

24V LED Strip Circuit - Switch, Breaker & Wiring Size Requirement

I am running a long LED strip (24V, 21 meter, 0.6A per meter, so technically 13A). The 24V PSU supplying power to the strips is to be connected to a switch that is rated 240V, 10A & 2400W. ...
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56 views

What can I add to a DC circuit, to limit the voltage to 24V and current to 16 amps?

I have a battery pack that can put out around 25V and 20 amps, but it needs to be limited to 24V and 16 amps. Update: This is a follow-up to my question from yesterday: Protected 18650 batteries ...
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6answers
2k views

How does a transformer increase voltage while decreasing the current?

Ohm's law states V=I*R. That means when we increase voltage we must also increase the current(I.) But transformer increases the current while decreasing the voltage or decreasing the current while ...
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2answers
49 views

Finding the current trough resistor in a closed mesh

In a closed mesh we have: simulate this circuit – Schematic created using CircuitLab The question is to determine the current through the 2nd resistor \$\text{I}_x\$. My work: I think of ...
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1answer
57 views

what is cut off current in dc motor?

This question is conceptual question. May it is easy for engineers to explain cut off current in DC Motor. In our formula, we are finding motor torque, $$T_{motor} = C_{motor} \times (I_{cut} - I_{...
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3answers
153 views

Op-amp: Virtual ground principle and other doubts [closed]

I can't understand some stuff about op-amps. Here is my list of doubts: If an op-amp amplify the difference between the V+ and the V-, how can it work if for the principle of virtual ground V+ = V-, ...
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3answers
138 views

Why does there flows no current through the common part of the circuit?

I saw there was a post asking the same question here but I still don't understand it. I am reading the book Code: The hidden language of computer hardware and software and the book shows the ...
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2answers
67 views

I'm working on a school Lab for a Constant Current source BJT and need a nudge in the right direction

I am stuck trying to determine the applicable formula for the load current. I have used \$I_b = \frac{Vin-Vbe}{(Beta+1)*Re}\$ and then \$I_L= (Beta)*I_b \$. The problem is I can't find a proper ...
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1answer
72 views

Identify the element among RLC

question : A two terminal network consists of one of the RLC elements . The element is connected to an a.c. supply .The current through the element is I A. When inductor is inserted in series between ...
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4answers
1k views

How current works

I apologize for the very basic question but I seem to be lacking some fundamental knowledge. I am using an infra red LED in a circuit and it seems like it is drawing around 15mA at 5v. I was told ...
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0answers
55 views

Calculate 100mAH battery with active and inactive value

A battery-powered remote wireless sensor uses 10 mA when active, 10 uA when inactive. How long will it run on a 100 mAh battery when it is: active for 10 seconds once per hour active for 10 seconds ...
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0answers
32 views

How estimate Current Consumption In minutes reference

Hello I hope somebody can give a short answer. I am confused about how estimate the current consumption of a Electronic Component/device. For example a led 20ma @ 3V or an arduino mini @ 50ma. If I ...
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4answers
650 views

High resistance, no current. What's the point of a potential then?

I am referring to this example: Why does it matter that the IC has a high resistance? What does this do for/to the IC? If there is a potential but no current, what is the point of using the IC when ...
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4answers
62 views

Normalised Current Transfer Ratio of Opto-Coupler

My understanding is that the Current Transfer Ratio of an opto-coupler defines the relationship between the current flowing through the LED, and the maximum supply current of the output. e.g. "5ma ...
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1answer
51 views

Electrical noise on wemos D1 mini

There is electrical humming sound coming from wemos D1 mini v2 module. I'm using 5v 3A power supply connected to 5v input pin. I suspect its the current input which cause sparking/humming sound. ...
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1answer
62 views

Amplifying Current from 0-20mA to 3A

I would like to drive a pump with a PLC. The PLC generates analog output signal of 0-10V with 0-20mA and the pump runs at the same voltage but 3A current. Is there any solution to this problem? Thank ...
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1answer
111 views

Boost Converter Output Ripple Current

I am designing a boost converter with the help of this TI app note My output Load current is 300mA and output voltage is 28V. I need to calculate the output ripple current. But in the app note, no ...
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2answers
114 views

Inductor Saturation Current and Temperature Rise Current

I have an inductor at the output of my boost converter. My output RMS inductor current is 271mA and the peak switch current is 1.3A. I have selected a 22uH / 2A Inductor as we select the inductor ...
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0answers
40 views

Mountain Bike Light Bar 18650 battery pack

I have a 6 Inch LED Spot Mini Bar Light which is used for vehicles, it uses 12-24 V and is rated at 18 W of power. I have some 18650 batteries which would work perfectly for this project. What would ...
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2answers
83 views

Will a live wire tester screwdriver work if I am hanging in air?

I have a very basic electric live wire tester. A simple device that otherwise looks like a screwdriver with resistor and a neon inside it. Image source WiKi I connect one end to the live wire and ...
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2answers
437 views

Will love to understand how the circuit works based on this schematics [closed]

Just a pure understanding of the workability of this circuit. why 7 switches?
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4answers
76 views

How to reduce the current of a battery with an unknown maximum amperage

I'm currently trying to heat a wire to a certain temperature and tests showed that the amperage needed is in the range of 3-4 A. However, I'm having a problem with how to supply such current to the ...
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2answers
67 views

Devices drawing current

I was recently reading a passage discussing the effects of a replacement (mobile phone) charging plug. Suppose that the original charging plug is marked 2 A and 10 V and is replaced with a ...
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2answers
55 views

Does ESP8266 deep sleep make sense while on the power supply? [closed]

If ESP8266 is powered via a dedicated power supply 220V AC → 3.3V DC. Is it worth it to put ESP to deep sleep in order to reduce power consumption? For example the indoor weather station, which ...
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1answer
40 views

Current mode operation of a Source Measurement Unit (SMU)

I'm studying semiconductor parameter analyzers. In particular, I have difficulties in fully understanding the circuit in the following slide, which represents an SMU operating in I-mode (i.e., it ...
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1answer
74 views

Where does -1 in BJT’s Ies equation come from?

I don’t know whether there is already a question and answer to this but I couldn’t find one yet. Regarding the following information from a text: The equation for emitter reverse saturation current ...
4
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1answer
57 views

Total current in a closed loop using Ampere's Circuital Law

I would like to reassure my concept on this question: I have 2 different ways to solve this question: Determining the direction of current in the loop using right-hand solenoid loop and adding ...
4
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3answers
933 views

Resistor Selection to retain same brightness in LED PWM circuit

I am making a simple LED PWM brightness control circuit. I am using a relatively high power White CREE LED, N-channel Enhancement MOSFET BSS316N and Resistor R. The circuit is as shown below. I am ...
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3answers
84 views

Is there no current between these terminals?

This is related to charge carries movements out of transistor terminals. Assuming a transistor in common emitter connection is biased properly where resistors are omitted for simplicity. Before asking ...
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1answer
79 views

USB cable for power delivery max voltage

I have a USB cable with the following markings on it AWM 80°C 30V VW-1 28AWGX1P 24AWGX2C Inside the cable there are 4 wires. I would like to use the VCC and GND ...
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1answer
74 views

Peak open-circuit current and applied voltage of transformer function

I know that the back-EMF equation tells shows that the peak flux density is proportional to the AC supply voltage. But what is the explanation for that the open-circuit current increases non linearly ...
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1answer
43 views

Is this way of plotting AC current gain in LTspice correct?

I want to plot the AC current gain versus the collector current in common base configuration. Ac current gain "alpha ac" for CB configuration is defined as the change occurring in collector current IC ...
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1answer
110 views

Ultra Stable Current Source At Up To 2 A [closed]

Can anyone suggest circuit(s) that can produce a very stable current source, preferably trimmable to close to 1 or 2 amps? Stability is the main requirement, all help is greatly appreciated. I have ...
5
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1answer
83 views

Are rated cable ampacities per conductor or per circuit?

I'd like to construct a cable using connectors DigiKey 708-1190-ND to connect a 20A LED to its power supply. The connector is rated "32A". In this example the connector's third pin will not be ...
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2answers
90 views

PCB problem - INA321 vias are too big

I am making a PCB using ULTIBOARD from NI. The problem is that I use a part called INA321 and for some reason I get the error that my vias are too close to each other when I place vias in the pads ...
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0answers
65 views

Current Transformers

I have a question about current transformers being used to measure AC currents. Say for example, we have a 50/5 amp current ratio, meaning that when there's 50 amps on the primary, there will be 5 ...
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0answers
49 views

Led driver compliance voltage

I want to design a led driver providing constant current to relative high power LEDS such as CREE XLamp series. These LEDs typically can be operated with 1A and upwards with a forward voltage of 12V ...
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0answers
29 views

Solving for open ckt voltage and short circuit current

I am unsure if I did the KCL for node A for the short circuit diagram correctly. I used the ia value from the open circuit and used it to find iy. Please let me know if I am on the right path or if ...
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2answers
89 views

Comparator as a current detector

I'm looking for a simple circuit that uses only a comparator (or an opamp) to detect the presence of a small current through a high-side current resistor. The idea is for a microcontroller input to go ...
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1answer
70 views

No Output Voltage On Power Mux

I am building a board based on a working reference design. I've obtained the assembled board based on my design but the '3V3_OUT' signal is failing to carry power anywhere on the board. The issue ...
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4answers
382 views

Opamp output to source and to sink

The output impedance of an ideal opamp is zero. The output of an ideal opamp acts as an ideal voltage source. The output of the opamp should be able to output very large currents (to source) and (to ...
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2answers
56 views

Confused on when to use RMS current or voltage in calculations (regarding rectifiers)

For question a, why is the power absorbed by the DC source : P=Vo*Io However, for the same exact question, the power absorbed in the resistor is P = (Irms)^2 * R Hence when do we use RMS current/...
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2answers
137 views

Class D amplifier - equation for peak current?

I'm trying to spec a power supply for a class D amplifier IC. I have figured out the maximum RMS current draw by taking the RMS power rating of the amp, increasing that to compensate for efficiency ...
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1answer
31 views

Do the dipole antenna edges have earth potential or is it a closed circuit made of co-axial cable?

I understand the shape of the dipole antenna, but how is it fed so that the current only flows through one direction during the half cycle? Even in a normal pole antenna, is there a ground at the edge ...
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1answer
46 views

Photodiode current vs. irradiance and finding upper limit current

1.) What equation could be used to calculate, or make a decent estimate of the current produced by a photo-diode from incident irradiance and its operating parameters. For example for this PIN photo-...
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0answers
22 views

LiPo ballancing circuit

I'm designing a circuit board to which I'll be able to connect multiple LiPo batteries (2-6S) and charge them in parallel without bothering user about balancing those packs firstly. So the charging ...