Questions tagged [current-limiting]

Current limiting is the practice in electrical or electronic circuits of imposing an upper limit on the current that may be delivered to a load with the purpose of protecting the circuit generating or transmitting the current from harmful effects due to a short-circuit or similar problem in the load.

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81 views

Do I need to limit the current on the inputs of a parallel load shift register?

I have a Parallel Load Shift register (SN74HC165) When connecting the parallel inputs, do I need to add a resistor to limit the current? And if so, can I use one resistor for all 8 Inputs in total? ...
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52 views

How to calculate current limiter resistors for ULN2803 and Relay?

I'm designing a digital I/O, and for the outputs I have ULN2803 and relays. I have the schematic below. The coil current of relay is 16.7mA, ULN2803's max input current is 1.35mA and output current ...
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22 views

CD4543B Direct LED Driving Capability

I bought some 7 segment decoders specifically the CD4543B and the datasheet https://www.ti.com/lit/ds/symlink/cd4543b.pdf mentions "Direct LED Driving Capability" Does that mean I do not have to use ...
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current limiting resistor for swing circuit (indcutor (probably))

for a project I modified a lucky cat/waving cat. The only part I haven't gotten so far is that for the arm to work with power from my dev board (or similar), I would need to limit or transform 3.3v ...
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1answer
81 views

Low voltage drop current limiter for charging supercaps with a MOSFET

I have an RPi that I want to give enough juice to auto shutdown when the power goes down. For this I'll use 2 supercaps of 6F (2.7V) in series, giving me plenty of time. Now, I was wondering if I ...
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148 views

How to limit current while almost keeping voltage same

I am supposed to design a power supply to a project. I have 3 alternative power supply designs for this purpose. However, one of them sucks huge current while giving enough current. My design is given ...
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62 views

Resistance issue in a triac-optocoupler switch

I have made the following circuit to control my water pump with Arduino(UNO R3). I have tried many resistors (calculated myself) to limit current in the optocoupler and triac, but failed to carry the ...
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38 views

How to work around odd LED strip current limiting?

I’m a theatre lighting technician (and electronics hobbyist), working on a project involving SK6812 RGBW addressable LED strips & strings. They use an 800kHz single-wire control signal, ...
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2answers
68 views

TL494/TL594 measure current with grounded load

Multiple examples of current limiting with TL494/TL594 suggest to use current sensing resistor between load(-) and GND. But I want load to be grounded. Can current sense resistor be placed above load(+...
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49 views

Can I Use a Transformer to feed a Mains current to a RPI GPIO pin

I have a standard mains (240v) motion detector that activates an outdoors lamp. I want to notify my Raspberry Pi when the lamp is activated. My plan is to use a 240v to 3.3v transformer that I have ...
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86 views

How to limit current using voltage regulator

I have a cheap little generic voltage regulator board which should allow me to select both the output voltage and the maximum output current, but I can't get it to limit the current properly. The ...
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43 views

Current limiter doesn't work

I've built simple current source with current limiter. Regulated part of the circuit is supplied by 10V from Lab Power Supply in which I set also current limit to some value. Idea is that U1 pushes ...
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27 views

What is the predictable difference of the voltage drop between the V+ and V- lines on a shunt resistor?

I am making an electronic speed controller, and the half-bridge driver I am using has a built-in overcurrent protection feature. In order to utilize this feature, I have to supply the pin (a ...
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73 views

Combining non-isolated switch mode power supplies in parallel into a single supply

I'm trying to combine several SMPSs each having a ~350VDC output @100mA each. Background: Purchased an unused batch of small DC->DC SMPSs in good industrial quality. Unfortunately they're too weak ...
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57 views

LM317 Constant Current vs Transistor Current Limiter

LM317 with Current Limiter configuration: Current limiter circuit with transistors: I am used to drive LEDs in my PCBs with LM317. However I recently came across this circuit which will cost less. ...
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29 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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133 views

Understanding DALI power supply

I am working on a DALI system and I came across this schematic for the DALI power supply in a Microchip app note AN1465: It says the power line can be 12-20 Volts but the current has to be limited to ...
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53 views

Trying to come up with a overvoltage overcurrent reverse polarity protection circuit, is option 3 done right?

I´m reading for the past week about P-Channel mosfet reverse polarity protection circuits. Then I´ve found this post http://kaktuscircuits.blogspot.com/2014/07/reverse-polarity-and-overvoltage.html ...
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71 views

Limiting current draw from a power supply

I have a power supply that can supply around -60 kV DC and 10 mA. This power supply provides energy to a device known as a fusor. A fusor utilizes a low current and a high voltage to ionize a gas and ...
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80 views

How to safely limit current for DC12v 30a?

I am plating my vias with electrolysis, and I need to safely limit the current so it doesn't go over 30 amps. The power supply I'm going to order is, you guessed it, 12V 30A. I've calculated the ...
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61 views

How does voltage/current limits work in switches?

I want to get a rotary switch, it says that it can handle 600 V and 40 A. I will use it to turn ON two DC brushed motors of 12 V 20 A. So, the voltage is way too high but the current is just right. ...
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69 views

Copper wire current ratings [duplicate]

I have seen a wide variety of different estimates for the maximum current rating for copper wire. For example, for 24-gauge copper wire, the Wikipedia article about "American wire gauge" claims that ...
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35 views

Reducing current in a circuit without reducing voltage [duplicate]

I didn't find a solution in the other similar posts or maybe I don't understand them. Here is my problem : I've got power supply with an output of 5V and 8A to feed 128 leds drawing 5V and 50mA each. ...
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45 views

Current limit a bus-powered usb 3.1 hub

I'm currently designing a bus-powered usb 3.1 hub. It will use a USB-C for UFP and 3 USB-A downstream. The hub will only be acting as a sink. As of my understanding, since it may be connected to USB ...
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67 views

Limiting current of a transformer used for resistance soldering

I'm working on a device capable of soldering wires to tiny components (3mm brass rings). I've used a PSU of a computer to make a resistance soldering device. Using the 5V line and a graphite stick of ...
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153 views

Limiting Cold Side Temperature on Peltier

I'm trying to cool my computer's CPU by sticking a peltier between the CPU and the heatsink, however I don't want to deal with preparing my motherboard and for condensation. Therefore I want to keep ...
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77 views

Raspberry PI Zero - 5VDC output current?

I was planing on using a Raspberry PI Zero W for å smart lamp project with WS2812b LEDs, to avoid separate power supply for the LEDs, my plan was to power the LEDs from +5VDC on the RPI ZW. The lamp ...
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1answer
115 views

What to consider when powering multiple devices in parallel?

Briefly about my background, which might inform the question. I'm currently self-educating myself on some electrical engineering on-the-job. I'm learning from Art of Electronics and some other ...
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113 views

DIY toroidal transformer spot welder

I've put together a toroidal transformer using a core suitable for 1500VA. The primary coil is around 70 turns with the secondary coil being just one. When I plug it into the mains (110VAC), I just ...
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734 views

Why are these LED current limiting resistors so big?

I'm looking at the charging circuit for a lithium ion battery that was made by Adafruit. Here's an excerpt: If there's a 5V rail from the USB port and a 470 Ohms resistor, is that limiting the ...
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325 views

Microwave oven: How can I temporarily limit the startup load?

Problem: It's a common problem for "NON-inverter" type microwave ovens to pop circuit breakers, and mine is no exception. There could be a huge number of reasons for this. Even though I thought I ...
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104 views

Current limiting a starter motor

I'm planning to try to build an electric go-kart. My idea was to use a 12V starter motor from a car to power it, since used ones are fairly cheap and easy to get. (I already have 2 of them to ...
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90 views

270v DC current limiting circuit

I have looked through some of the current limiting responses, but don’t see any close to what I’m working on for my project. I have an EV system running in around 200 - 270V DC. I want to build a ...
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631 views

Digital Current limiting with MCU

All current limiting circuits I've found until now use some sort of analog Logic with Op-Amps to limit/control the current. (Why) is no digital current limiting used? I would imagine a shunt resistor ...
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2answers
170 views

Does this neon indicator light require a resistor to limit current?

I've got a few of these indicator lights from LEECRAFT/VCC, they're marked "tineon 3600" and "125V 1/3W". According to this page: http://wiki.diyfaq.org.uk/index.php/Neon neon lamps require a resistor ...
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88 views

Adjustable voltage source 10 – 50 V and adjustable current limiter 2 – 70 mA

I would like to build a source that gives on the output an adjustable voltage from 10 V to 50 V and that current be limited from 2 mA to 70 mA or make some circuit that let me choose 2 mA, 1 0mA, 50 ...
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117 views

Is my understanding of this level shifter correct

I am considering using this TI LSF0102 level shifter in my circuit - but would like to understand, based upon its datasheet, if I have my understanding correct. It says it has a 100mA current rating, ...
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34 views

TPS562208DDCT current problem

I have attached a PSU design which I have created. The input voltage is between 12 and 24V DC. The first stage creates an isolated output voltage of 7V that is then fed into the two TPS562208DDCT (...
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26 views

IT characteristic implementation of motor protection circuit

I am trying to implement The IT - characteristic feature for motor protection device.There are 2C,5C,10C curve feature . can someone suggest me how it can be implemented in C code. Is there any ...
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85 views

Calculating value of a current limiting resistor in a constant current circuit?

I am using 12 leds in series with 3.0-3.4 v forward voltage and 400-500mA forward current (these values are from the datasheet). I am using a constant current led driver(24-40v and 580mA). My problem ...
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1answer
240 views

Current limiter using pnp transistor

I have below design and want to know it is correct or need to change anything. Details are as below Input voltage is from 18V to 40V and can draw only 2mA current from source voltage. so I have ...
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67 views

Inrush current limiter circuit for filament bulb - comparison

Context: A 12V power supply is switching on externally connected 12V filament bulbs. The power supply's load switch implements an electronic resetable fuse (13A/τ=15ms) in case of an external short. ...
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114 views

What's inside this current limiter?

This component was inside an isolation transformer. It's obviously for limiting inrush current, but how does it work and what is inside? I believe it's a relay of some sort, switching a resistor in ...
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530 views

Current limiting source using opamp

I wanted to know if I'm correctly thinking. The idea for current limiting is to force the opamp to output the correct voltage to control the MOSFET. So the maximum voltage possible is somewhere ...
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3answers
88 views

Surge or other suppressor I can use, to prevent tool blowing fuse if blade sticks [closed]

I want to say up front, that this question involves minor modification (transient surge/current suppression) to the power supply side of a power tool. Usually I'd be the last to do anything like this (...
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109 views

active current protection with diode instead of shunt resistor

Is this current protection technique going to work? I came up with this because I want to make a current protection circuit and I do not have a shunt resistor at hand. I think the circuit should work ...
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403 views

Limiting current to 20A with 48V in

I'm an electronics newbie and I need some help/advice with a project. So basically I need to make a sort of programmable power supply module (or at least that's what I think I gotta do). I got a DC ...
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102 views

Resistor or no resistor between this IC and the pmos GATE?

I'm using this IC (https://www2.mouser.com/datasheet/2/609/ADM1270-878589.pdf). This IC controls the GATE of a pmos. I'm thinking about using this MOSFET (https://www2.mouser.com/datasheet/2/389/...
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131 views

Laser Diode Feeding

Edit: Laser diode info page I have a basic question about laser diodes. For a 14-pin butterfly package as shown below. I know that I need to control the current going in to the laser diode, but I don'...
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128 views

Op amp current regulator

This is probably a marginal mistake. This circuit, a current regulator: simulate this circuit – Schematic created using CircuitLab Works fine on simulation. However, it does not once built. ...