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2answers
43 views

How to make USB smartphone charger? [duplicate]

I want to make a USB cell phone charger. I know USB operates in 5 volts which means i need to drop down voltage if i have battery potential greater than 5 Volts. I have 12 volts sealed lead acid ...
2
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1answer
71 views

Very odd open-drain output design

I ran across a open-drain design and am baffled by the resistor between the nFET source and ground. There are only two purposes that I see it could serve. 1) It's series source termination, matching ...
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1answer
46 views

Leftover current after current limiting resistor

This question is related to my another question here. In crux, I would like to sink current of TLP521 via 74HC595n shift register. The TLP521 is connected with a resistance such that the current is ...
3
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2answers
155 views

How to limit current precisely?

I would like a way to limit the current of a circuit to exactly 100mA (+/- 2-5%). This is on a relatively high voltage circuit (100V to ground), and the current is normally pulsed with pretty fast ...
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1answer
55 views

Choosing wattage for current limiting filament bulb

I am building a fully featured breadboard/prototyping box for audio circuits and would like to include a current limiting light bulb that will be in circuit when I apply power to the box and then I ...
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3answers
75 views

Current Limiter, can someone troubleshoot this circuit?

so I am trying to limit the current output with x2 3904 transistors and a sensing resistor. This is currently what I have, but am not sure why it doesn't work. That current supply is going to be a ...
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1answer
40 views

Current limiting AC

I am currently experimenting with electrolytic marking. I use a DC bench supply with a current dial so I can drive the reaction with a constant current to keep the marking steady and as a plus keep it ...
0
votes
1answer
69 views

Exceeding voltage ratings on microcontroller pins using series resistor

I've been designing a circuit which requires a microcontroller to read a voltage above its current VDD or below its current VSS. I've done this once or twice before by putting a large-ish resistor in ...
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2answers
105 views

Current limiter with low voltage drop out

I am looking for way to limit the output current from a LDO (Vout = 5V) to max. 150mA. I found only this circuit but the problem with this circuit is the voltage drop Vbe of the transistor Q1 and ...
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1answer
51 views

Is the excess of current the only problem in a motor overvoltage?

I'm designing a Full Bridge for a Brushed DC motor control. My circuit will have a current measurement, so I'll can control the output current, sinked by the motor. Whit this current control, I think ...
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1answer
34 views

Charging questions, current limitation and voltage

I'm having few issues with chargers, current delivered to a device etc... just need to connect the dots I guess. When I connect a phone to a charger for example IPhone which is rated at (5v,1A max), ...
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2answers
44 views

Forward current for assorted LEDs

I have an assortment of T1 and T1¾ LEDs from sampler kits and beginner kits. The kits have sketchy documentation, with missing or inaccurate part numbers. I was able to track down datasheets for some ...
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2answers
76 views

Simple SPST Switch Circuit - Pull-down Resistor VS. Current Limiting Resistor

Super Noob EE question: Here is my quick draw-up of my SPST switch circuit schematic. I know I probably did not do this right, but if it gets the idea across, then thats good enough for me atm. ...
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2answers
55 views

User power supply current limit to avoid current limiting resistors for LED

everyone! I would like to know if I can avoid to use current limiting resistors by pushing my power supply to its limits (it already sounds not like a good idea... btw...). Say I have a 3.3V power ...
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2answers
83 views

Inrush Current Limiter Failure

I work for a company that builds electric motors, within the last few years they've started building control boards from brush-less dc motors. On the incoming power we have an Inrush Current Limiter ...
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0answers
37 views

How to restrict power output to a USB client?

...or, how not to charge my phone when I'm using it as a GSM modem in USB tether mode? I've asked this on Unix&Linux but it seems there's no simple way to do it in software. The problem: In USB ...
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2answers
101 views

Current limiter its not working as it should?

I have created a voltage regulation circuit using op amp and feedback resistors, now I am trying to add a current limiter to the circuit. have read how to create this using two transistors and a ...
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3answers
477 views

How do I build a 10uA current source/limiter?

I need a constant current of 10uA through a variable resistor in the 100k values. I need to inject the current into that resistor and I need the resistor to be connected to Ground such that I can ...
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1answer
118 views

Is there a component that limits current and has a low resistance<0.1Ω

I want to limit the current to 6A. The (roughly resistive) load draws maximum current 9A at 12V. The load voltage is adjustable between 1.5V and 12V. I know that limiting current cause not to reach ...
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2answers
230 views

Limit drawn current but not voltage (LED driver for 100W LED)

So I have serial connected 8 LiPo's with corresponding controllers to monitor the battery pack. Now, they deliver 32 volts which is precisely what I need but they deliver way to much amperage compared ...
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3answers
92 views

How should I current limit a LED matrix?

I have an LED matrix which has a maximum peak forward current of 90mA and average forward current of 13mA per LED (dot). If I power only one LED at a time, this one LED will have a very large current ...
0
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1answer
50 views

How to implement a current controlled voltage source, or a comparator that trips once a certain current is reached?

I have current flowing through a CCVS, once 10A is reached, the CCVS puts out 10V, which takes a comparator's output high. The current that goes through the CCVS continuous to the load. Is there a way ...
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1answer
56 views

Voltage stepping and current reduction

I'm designing a drone to use a relatively new form of propulsion, electrostatic fluid propulsion, which requires extremely large voltages (in the order of 10-100kV) running through a wire to ionize ...
2
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2answers
590 views

What's the difference of placing multiple resistors and one resistor for limiting the current of LEDs?

I'm looking at a diagram and wondering if I could use just one resistor to limit the current of the LEDs instead of multiple resistors so that the cathodes are all connected to the same resistor. ...
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1answer
122 views

Comparison of the efficiency of DC motor current limiting / control methods?

I'm using the wheels and motors of an RC toy car as a simple robotics platform. The car has 2 motors, one drives the back wheels, the other steers the front wheels. The steering motor is stalled by ...
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3answers
148 views

Diode Drop vs Open Drain Output Tolerance

I have an LED Driver IC that states a 5.5V tolerant Open Drain Output. It's Absolute Maximum section indicates 6.5V with a note saying "The input negative-voltage and output voltage ratings may be ...
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4answers
452 views

How do current limiting resistors work between ICs?

In a simple battery+resistor circuit with a fixed voltage, the resistance of a series resistor determines the current flowing through it. But what happens if this resistor is placed between two ICs? ...
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1answer
111 views

Current limitation of a power supply by using transistors

DALI standard limits the maximum current as 250mA. I have a 12V source that is capable of supplying more current. I implemented from one of Motorola reference design the below schematics that limits ...
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1answer
397 views

What happens if I supply 18V to a 12V lighted switch?

I am fairly inexperienced with electrical engineering and usually just wing small things I.E. a current project. Basically I have a project box, with a 12v arming switch with a red light in it. ...
0
votes
1answer
99 views

Voltage limiter with LM358

I have a problem with circuit, because I don't know how to design a voltage limiter. I connect to the input (In) sensor that generates signals with range of 240mV to 940mV. Next, The signal output ...
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1answer
275 views

USB current limiter and under/overvoltage protection

I know recent motherboards already provide these, but lately USB ports are also available in many different gizmos (smartphone chargers, TVs, standalone players, etc.), which I am often tempted to use ...
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2answers
98 views

Protecting a circuit from the effects of a capacitor's charging

During its first outing, I managed to burn out the (control circuitry) of two of the batteries connected to my LED jacket (see this, this and this question for context.) I thought I should have been ...
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2answers
107 views

Limiting mains current

What would be the best way to limit mains (240V @ 50Hz) current? I want at least 1A of current. The output should be AC 240V at any frequency greater than or equal to 50Hz. It should be able to endure ...
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1answer
49 views

Safely Driving a Brushless Motor

I am currently building a quad-copter out of an Arduino. I decided to make my own ESCs using MOSFETs, EMF sensors, and the Arduino. These are the motors that will be driven: ...
3
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1answer
94 views

LT1084 as Current control Regulator

I am using LT1084 as a current control Regulator. Circuit shown below Since the transistor Q2 is controlled by a PWM pulse so output voltage of LT1084 is varying as shown below Since it is used as ...
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2answers
246 views

Batteries & Output Current Limiting

I am currently working on a project that uses a 9.8V 1000mAh battery to power a solenoid, and as I understand it (please correct me if I got this wrong.) a battery capable of delivering 1000mAh is ...
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2answers
891 views

Maximum op-amp output current

Im looking to drive an LED, but am not sure if i should use an op-amp or bjt configured as a switch. Is it possible for an op-amp to source roughly 10mA; the current needed to drive an LED in series ...
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1answer
615 views

Designing a current limiting circuit for my project

I've got a small DC brushless motor for which I would like to set a current limiting circuit as a protection against over-current. I thought I could pull it off with a simple fuse (or those current ...
2
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2answers
269 views

LM3485 current limiter (\$R_{adj}\$) value selection

I have what I believe is a working buck converter design centered around the LM3485. It's intended to be a Raspberry Pi power supply. The schematic is at Pi Power schematic, which I copy below. ...
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4answers
473 views

Is it reasonable to use a current limiting diode in place of a fuse?

I'm trying to source some fast-blow 5mA or 10mA fuses but Littelfuse has discontinued the only reasonably affordable ones I have found. My circuit when operating properly will not output more than ...
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0answers
41 views

DIY Power bank for router? [duplicate]

I'm an electronics enthusiast living in a country with a lot of power cuts, especially through the summer. I want to build a 9V <1A DC power bank for my internet router running on a AC->DC power ...
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1answer
950 views

Need help calculating resistor values for IR LED Driver

I'm wiring an IR LED driver for an Arduino project I'm prototyping. The Arduino will be run at 5V, and I'm planning on using it's 5V output to drive the transistor that runs the LED The circuit I've ...
1
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2answers
309 views

Peak current limiting motor

I've got a motor driver which can take 3A. But my motor seems to draw more than 3A as peak current when it's been turned on. And I would like to get rid of that since it blew up my motor driver a few ...
0
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1answer
165 views

Limiting the current on a PC power supply

I want to use a PC power supply on three 12V stepper motors. The problem is that I want to limit the current of the 12V DC output to 3A maximum for each of the three motors. The power supply has 34A ...
4
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1answer
736 views

Does this circuit regulate current?

I am being told that the circuit below will regulate current, I am wondering how true that is and how exactly does it do it if so. As far as I can tell: two NPN transistor with their bases biased by ...
2
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1answer
95 views

Safe way to wire CMOS ICs together

I have a question about the safety (to the ICs) of wiring the output of one IC directly to the input of another IC. simulate this circuit – Schematic created using CircuitLab For ...
2
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1answer
152 views

How do variable current limiters work in power supplies?

Bench top power supplies often enable you not only the set the voltage, but the maximum current. How do these bench supplies provide this variable current?
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2answers
491 views

LM350 current limiter

Why is the following circuit an adjustable current limiter? It looks like a adjustable current source to me. EDIT: I know the difference between current limiters and current sources. Lets analyze ...
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1answer
284 views

Buck boost converter for lipo 6s charge info request

I need to dimension a Buck boost converter to charge two LiPo battery packs 6s 20ah starting from a variable input voltage. Both packs have their own PCB BMS board. This one: ...
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3answers
730 views

Determining maximum current through 18 gauge wire in robot arm

For a robotics application, I'd like to power some external electronics and sensors off the logic circuit in a robot arm. The components are a computer (19V, 65W => 5A), 2 cameras (1.2A), 1 light ...