# Tagged Questions

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 ...

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### Need assistance in choosing diode for seat heater circuit

Background: I have been working on car seat heater circuit. I purchased the universal seat heater with manual 2 level (high and low) switch. Instead of manual switch, I re-wired the seat heater ...
49 views

### why Commutator power capacity is limited

A commutator's power capacity is said to be limited to a few megawatts. What are the reasons limiting it? I thought it could be like brush resistance and spark strength. What is the maximum voltage ...
57 views

### Voltages to keep my circuit running at 200mA with NMOSFETS

Im trying to build a circuit to send information using IR led, using pulse signals my leds (TSAL6400) operates at 1.35V, and their maximum pulse current is rated 200mA After struggling a bit with ...
70 views

### Why do we need to find the current?

I am beginner in electronics. What i came to know until now is that mostly we have to find the current in a circuit in our text books. I wonder what useful work we do after finding the current, dc ...
127 views

### How to increase the current in this circuit?

Im trying to build a circuit to send information using IR led, using pulse signals (Im trying to mimic a home appliance remote control). My leds (datasheet) operate at 1.3V, and their maximum pulse ...
99 views

### Smartest way to use current limit using LM317?

As i understand, using this circuit: Will cause the current to go right through the POT and resistor, which will generate a lot of heat. Is there a better way to use current limiting with LM317 ...
37 views

### Driving a 5V IR led with a 5V charger?

I'm trying to build a remote control with IR led. I'm experiencing low range with my 1.5V, If=50mA IR leds, so I looked for and found a 5V, If=100mA IR leds. twice the current, hence probably better ...
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### Generic question about interfacing a microcontroller with a device: when is the current limit a problem?

I have an Arduino Board, to be precise many models, but let say I want to interface a ATmega328p with another integrated circuit (all is running at 3.3 V). In this case I want to connect Arduino with ...
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### LTC1153 current trip off IC

I am using an LTC1153 IC, with an IRLML6346 MOSFET. I am supplying a 3.3V rail. Now, the output is being fed to an arduino board and the supply works. The Gate pin gives out about 7V (in conformance ...
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### Where can I use my ammeter to measure the current set by the current limit potentiometer?

Here is the circuit in question: (http://i.imgur.com/Jmo6mzL.png) The circuit is an adjustable power supply that I have put together (can be bought here) and I am working on putting it all together ...
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### What is the Maximum Current an Arduino can Supply? [migrated]

I was wondering how much my Arduino I/O pin can output when it is set at Output and is at High. I am using an Arduino Uno R3. Thanks in Advanced.
100 views

### How a sensor supply circuit should be? [closed]

i am looking for sensor supply circuit for a sensor. The sensor requires bipolar +-6V to -15V DC and 10 mA power consumption at 6V DC (6V*10mA=0.06mW). Also power supply of this sensor requires less ...
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Goodmorning all, Here my very first question so I may be asking something that is may be already answerd but I couldn't find, My question is : How is current limiting achieved in modern IGBT based ...
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### Adjust the power of laser diode on both CW and pulsed mode

I am working on my graduation project to build a laser unit, i am supposed to control the power of laser diode when operating in pulsed mode and continuous mode. firstly, i had the pulses from ...
62 views

### Help using transistor in active mode as a current limiter

Brief context: I have a small solar panel, nominal properties are 0.6W, 6V, 100mA. In given conditions I want to measure the maximum power it can produce - I do not want to do anything with this ...
44 views

### Using AC fuse for DC & DC fuse for AC…!

Recently I visited a site where I saw that in an inverter AC fuse are use for DC..it is quit odd for me..!!! Is it ok to use the same? What are the factors to be considered when we use AC fuse in DC ...
43 views

### Over Voltage Protection/Surge Suppressor Circuit

I have a 12v Solar system that powers a WiFi radio (that needs 24v PoE). So I have a step-up converter feeding the Radio... worked great, until my 24v step up started to fail and was passing way too ...
88 views

### current sense circuit - High side sensing/Low side sensing

I want to measure the current through the 2 ohm Load resistor.I have read about high side and low side sensing.But I am confused about which method should I use in my case as the FETs are part of ...
53 views

### 3V Current source with low voltage drop

I'm trying to make a IR laser diode driver which needs 1.9V and ~80-100 mA constant current. Most of laser driver circuits in web has LM317 as a current source but that design has always voltage drop ...
56 views

### Given Vf across a LED, what is the current draw?

I have sourced some LEDs from everyone's favorite high-quality electronics marketplace, eBay. I have a simplistic "datasheet" for the 7-segment LEDs that I purchased, which show a Vf of 3.8v across ...
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### Question about Power MOSFET current limting

I am studying current limiting technique for Power MOSFET(P-ch). The material is AN1542(Active Inrush Current Limiting Using MOSFET) ...
59 views

### 480 VDC Series Battery Bank - Solar PV Charging Current Feedback Control Circuit

I have a 480VDC Lead Acid Battery Bank (40 x 12VDC 50Ahr Batteries in Series) directly coupled to a 5.0 Kilowatt Solar PV Array [with an output range of 560-580 VDC and maximum output of 8.9 Amps). ...
105 views

### Current limiting with MOSFET

i want to limit the current through a MOSFET (high side) as simple as possible. The MOSFET will switch 600V and approx. 150mA for 1-2 seconds. The focus really lies on simplicity. I know that i can ...
99 views

### Is a resistor needed between logical pin and base/gate transistor?

I'm using a logical pin output (3.3V) to drive a NPN darlington transitor with the max current possible to minimize the fall and rise times. My microcontroler has a 20mA max output current per logical ...
71 views

### Need assistance with current limiting resistor for LED

I am seeking some advise on a making an infrared light source. I am using IR LED SE-5455-2. I have found some calculators on line but the results vary. I have also read many threads here. I am ...
119 views

### Detecting a coil is fully energized

I'm working on customized ignition system and want to implement the final stage as robust as possible. The ECU (Engine Control Unit) provides TTL level control signal to drive ignition system. The ...
105 views

### If I drive an LED whose forward voltage is 2V with a source that's 3.3V limited to 20ma, will I harm the LED?

Background: I built a 10x20 LED matrix for use inside a jack-o-lantern. The matrix is driven by 74HC595 shift registers that are connected to an Arduino. I've attached the Vcc of the shift registers ...
112 views

### Why sample current via lopsided resistive divider?

I'm studying the constant-current circuit of the Agilent E3610A 15V 30W DC Bench Power Supply. The entire schematic is at the end of the user manual, but I've redrawn the parts of interest here for ...
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### How much hold current is consumed when there is no load?

Given a 24V 1A motor with no actual load connected (just a piece of orange tape so we can see the shaft moving). How much current will the motor use if I configure the driver board for 2A maximum ...
136 views

### How to limit current in order to power small car radiator fan with laptop charger?

I'm trying to do a makeshift small grinder/sander out of a car radiator fan, but I want to power it up with a laptop charger for convenience. Since it's a salvaged fan, I wasn't able to look up its ...
167 views

### BJT Current limiter for linear power supply

I am trying to design a current limiter or my LM317 based power supply using this schema. The power supply must be able to provide a maximum of 1.5A@30V. I made some calculations and I would like to ...
188 views

### How does this power supply circuit work?

This is the circuit of a power supply with adjustable output voltage and current, and I wish to understand how it works: What I did understand: R1 T1 VD5 - they form a voltage divider which ...
18 views

### How to determine limiting load of a motor which uses separate Over Load Protection Component

I am using an dual voltage electric motor of 1.5Hp and RPM of 1750.Dual voltage motor works on 110Vac and 230Vac but with single 60Hz frequency. There is no over load protection built-in on the motor, ...
153 views

### Using transistors to prevent short circuit / current limit

I am designing a circuit where I want to protect Q1 from current overload and popping in the event that Rl is a short. The length of wire in a short circuit situation is 0.7 ohms. Usually Rl is 10 ...
81 views

### Function of the FET in LM350/LM317 programmable current limiter

My question pertains this circuit which is from this question, which in turn is a circuit straight from the data sheet. I don't understand the function of the FET in this circuit. Surely, with the ...
99 views

### Transformer Current Limiting

I Rewired A MOT (Microwave Oven Transformer) To have an Output of 40V and a center Tab With No load the primary Gets HOT really fast. I measured the current draw with no load and it pulls about 10 ...
93 views

### X-Ray tube Current Control based on PWM

I want a control module to be implemented in FPGA(Altera Cyclone IV running on NIOS2) using VHDL which controls current flow to a X-Ray tube. The scenario is I have the expected current value say ...
54 views

### Current clamp circuit after buffer amplifier

I'm building a voltage supply that uses a DAC to convert a binary string into an analog voltage. The DAC can't source a lot of current, so I'm using unity-gain amplifiers after the DAC output on each ...
59 views

### Current limiter of negative/positive pulse

I have pulse with both negative and positive sides, say -4v to +4v. I want to limit the current for both sides to 1mA. I know how to limit the current of a 0 to 5v pulse using two transistors but I am ...
251 views

### Simple function generator: is current-limiting/short circuit protection/impedance matching necessary?

I have designed a function generator with the intent to provide test signals to a microcontroller or ADC of some other device. However, I may forget that a year down the line and plug it into some ...
58 views

### why is my differential amps error related to load impedence?

So ive built up this circuit, as a simple current limiter. After making sure the output is null when the differential is 0, i get different errors depending on the load impedance even when the both ...
76 views

### Explanation and solution of an error in Differential Amplifier Current Soruce circuit

So ive built up the following schematic as a simple current limit circuit. When the current limit is not in place, ie the PNP is conducting "fully", I null any offset errors in the Differential Amp ...
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### Reduce output current with same voltage of circuit

I have a lm2596 module and given a 12.5v 3A input to it Now i derive 5v 3A max output from it The prob is the circuit when connected as a charger to phone heats up and doesnt charge well or burns out ...
231 views

### How to deal with inrush current tripping circuit breakers?

I have a temperature controller supplied with 230VAC via a 0.5A circuit breaker curve C. The thing is, the MCB trips as soon as power is turned on. I have measured the inrush current profile without ...
42 views

### Need to control 100 Watt Pump With 15 Watt Float Switch

I am an inexperienced hobbyist So My Question may be obvious, but thank you for the help. I have a 12 V battery, which is powering two 12 V pumps. It is a 100 W pump which runs at 7 A on average ...
100 views

### Limit current with fewer resistors

Arduino digital pin in OUTPUT mode have low impedance, is it safe to limit current through two leds (connected to two output pins) with one resistor, not two (knowing that leds will go dim and current ...
52 views

### Current Regulator IC/Transistor [duplicate]

Can anyone suggest a Current Regulator that can bring down 2A to 40mA... I'll be needing 40mA to power my arduino... I'm not that keen in electronics so pls use simple terms in explaining things to me ...
424 views

### How to determine current limiting resistor values for push pull amplifier driven by op amp?

I'm looking to increase the output current drive of a high voltage op amp using a push pull amplifier. The OPA454 datasheet includes an application circuit to do exactly this, and includes some ...