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2
votes
1answer
151 views
+100

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. ...
0
votes
4answers
101 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 ...
0
votes
0answers
35 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 ...
1
vote
1answer
74 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
vote
2answers
157 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
votes
1answer
94 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
votes
1answer
418 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
votes
1answer
67 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
votes
1answer
62 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?
0
votes
2answers
147 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 ...
1
vote
1answer
113 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: ...
1
vote
3answers
112 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 ...
2
votes
2answers
138 views

What is the correct way to handle inrush currents from a DC/DC converter with short-circuit protection?

I have been using CUI VESD2-S24-D12 to generate 24V to run a circuit board. That regulator has been EOL'd with the recommended replacement being PEM2-S24-D12. The two are effectively identical except ...
2
votes
1answer
254 views

DC motor starting and stopping

I'm powering a motor, and instead of rotating at a constant rate, it rotates roughly a third revolution every half second or so; the rotation keeps starting and stopping. There's no load on the motor, ...
3
votes
1answer
152 views

When a pin needs to stay LOW or HIGH, is it okay to connect directly to VCC or GND?

For example, I'm using an Exar Exar SP3220EBCY-L RS-232 transceiver and the typical application loop back test shows that the EN pin is connected to GND and the SHDN pin is connected to VCC. Should I ...
0
votes
1answer
64 views

protecting a sensor component from high spikes when switching power on

I have an electrical scooter which has a "Hall Effect Sensor" in the handle-bar, measuring the magnetic flux to determine the amount of "gas" or gauge. This sensor tends to burn out quite frequently. ...
0
votes
0answers
59 views

Regulation of DC/DC output voltage and current

I found interesting topic recently, here is it: What is causing the oscillation in the feedback loop of an SMPS? Could somebody explain to me, how does this circuit supposed to charge deeply ...
1
vote
0answers
87 views

Voltage-following, short-circuit protected PSU circuit

For a PSU regulator circuit with these requirements: 0-14v adjustable output, set by 0-14v signal, accurate to +/- ~200mV 20A current limiting +/- ~2A which reduces output V as necessary down to 0V ...
0
votes
0answers
71 views

Need to build a current/voltage limiter for Arm cluster

It's been a while since I dove into electrical components (since college) so bear with me here. I am building an ARM cluster here at my house using ODroid-U2 boards and I want to use a battery bank ...
3
votes
1answer
88 views

How to limit current of an AC signal

For my project, I'm trying to work with the principle of electrovibration. This principle is about simulating textures using low current electricity on an insulated conductive surface (see Wikipedia). ...
4
votes
1answer
231 views

Current measurement in a Buck Converter

We have developed a prototype of a PID-regulated Buck converter made around the AVR XMega. 6-17V at the input, 5-10 on the output, 15A current limit, 500kHz PWM switching. The issue is, how to make ...
1
vote
4answers
100 views

How is current controlled in high power applications?

When working with electronics, it is quite easy to regulate current with a resistor, potentiometer, switcher, etc. But take a simple high power application such as an electric stove. What method is ...
0
votes
2answers
166 views

Are there any single chip solutions for single cell LiPo battery protection? If not, any references?

I can't seem to find one, but does anyone know of a single chip solution for LiPo battery protection on a single cell/3.7V battery? Looking for things like over-current/overvoltage/undervoltage ...
4
votes
3answers
290 views

Improving a simple bipolar current limiter

Is there a way to remove the Vbe dependence on bipolar current limiters, or at least, lessen the effects of process variation & mismatch in the topology below? Vin is nominal 22V, but could ...
1
vote
2answers
130 views

Smoothing current drawn by PWM load

I have a PWM load which draws its current from a regulated DC supply. The supply and load will be separated by some distance, and I'm worried that the rapid changes in current through the current ...
1
vote
2answers
580 views

How to limit base current in transistor when collector current is unknown?

In the followig circuit I am trying to replace a push button with a transistor: simulate this circuit – Schematic created using CircuitLab In the schematic SW1 is the push button that ...
0
votes
0answers
102 views

measure resistance circuit when I have an lm334

I have a circuit simulate this circuit – Schematic created using CircuitLab this circuit without the lm334(current limiter) should produce some kind of voltage on R6 when R5 and R4 are ...
1
vote
1answer
364 views

Current limiting on a stepper controlled by L293D on an arduino board

I currently have a bipolar stepper motor connected to a l298n, with one resistor to each coil. The problem is it draws a lot of power when there is no need to, and limits the maximal power of the ...
3
votes
2answers
176 views

Small battery cut off when fully charged

I am working on a small 1.2 V battery. I want the charging current of 7 mA to stop when the battery voltage reaches 1.5 V. What cut off circuit should I use ?
0
votes
0answers
68 views

Do film capacitors need to be isolated and current limited during the burn-in process to prevent them from discharging into one another?

Do film capacitors such as polypropylene and polyester film capacitors need to be current limited with resistors to each unit and isolated during the burn in process to prevent discharges into other ...
1
vote
1answer
87 views

Is there such a thing as a resistive bus bar to substitute many resistors?

I find myself in the position to design Burn-In racks for a capacitor manufacturing company. I am trying to replace the multitude of resistors on boards that limit the current and isolate each ...
1
vote
2answers
351 views

Transistor current limit circuit - power handling?

I am designing a simple current limiter, which charges a large (4.7mF) capacitor with a charge current of (roughly) 500mA from a supply voltage from about 10-20V - see the below circuit. My dilemma ...
4
votes
4answers
221 views

Can electronics be damaged by under-currenting it?

Someone just asked Can electronics be damaged by undervolting it?, so now I am going to ask under-current. Let's say something requires 10A, 12V, if I limit the current to 5A, could anything go wrong? ...
14
votes
4answers
2k views

Does an over voltage, over current and reverse polarity protection IC exist?

I'm designing a circuit that has the following protection requirements: Reverse polarity Over voltage (60v max) Over current (approx 1A) There's quite a large input voltage range, 10v to 60v. 48v ...
3
votes
1answer
133 views

Is there a way to plot the current to charge a capacitor given that there is a max current in the circuit given by the power supply?

I'm trying to determine the maximum current of a circuit while charging a capacitor but since the power supply has a maximum current of 20mA that is going to extend my charge time longer than the RC ...
0
votes
2answers
344 views

General Questions about PIC24 MCU Input and Output Pin Impedance, Voltage, and Current

I'm having a mental lapse. Try and help me make sense of a few basic things concerning microcontroller pins at the hardware level, please! Correct me if I'm wrong… in the circuit of Figure 1 (see ...
45
votes
1answer
5k views

How can I efficiently drive an LED?

I understand that I can not connect an LED directly to a battery because it will draw too much current. Thus, there must be something else in the circuit to limit the current. What options are there? ...
7
votes
6answers
1k views

Prevent overcurrent while filter capacitor is charged

I have this circuit: On start-up, the power supply experiences an overcurrent condition, because when the capacitor is charged, it looks like a short circuit as seen from the power supply. How can ...
3
votes
1answer
373 views

Driving servos using microcontroller and current limiting

I am new to electronics and would like to design a PCB that uses an Atmel microcontroller, and powers three servos. I was thinking of designing the PCB with a single power supply. The servos I have ...
3
votes
3answers
849 views

Do I need a current limiting resistor when powering an LED below its forward voltage?

I've reviewed the questions: Why can you use an LED below voltage? Is a current-limiting resistor required for LEDs if the forward voltage and supply voltage are equal? But combining them begs ...
1
vote
2answers
339 views

Motor Current Limiting Algorithm

I am building a H-Bridge controller dor DC motors, and I want to add some current limiting on it. Does anyone knows a good algorithm for doing so? I am planning to read the current, and if it goes ...
4
votes
2answers
6k views

How to do a simple overcurrent protection/circuit breaker circuit for 12V 1-2A?

We're developing an I/O shield for Arduino (sort of) and having four FET controlled output connectors with approximated 12V 1-2A load each. I need all these four outputs to be short-circuit protected ...
0
votes
2answers
2k views

wiring LED's in parallel - need series resistor?

I would like to confirm something I have inferred through my looking into LED wiring and also have a couple questions answered. For the sake of the examples below assume the source voltage is 5v; my ...
7
votes
3answers
2k views

Why is LED lighting up despite Supply voltage < Forward voltage

I have an LED which has specified Typical forward voltage of 3.5V and Maximum forward voltage 3.9V. I applied 3.3V across it with a 300 Ohm resistor in series. Why did it light up? I am wondering if ...
18
votes
2answers
662 views

Solution for adapting to USB current draw limits?

Summary: I'm setting up a USB-powered Li-ion charging circuit and would of course like to draw the maximum charge current possible situationally -- but also want to ensure I don't violate the USB ...
0
votes
3answers
2k views

Protecting diode bridge from higher current

I have designed a battery charger circuit. The circuit is simple AC to DC power supply circuit, it is composed of a 220 Volt to 16 Volt stepdown transformer, a diode bridge and a capacitor. Now the ...
8
votes
2answers
725 views

What is high side current limiting?

What is high side current limiting? While google searching for the term I have found ICs that describe their application as "high side load switching". Is this the same thing or something utterly ...
4
votes
2answers
2k views

Charging capacitor bank with current limiting circuit

I would like to charge a capacitor bank with a 4.8 volt supply that I have. With the help received in response to this question, I now have a a useful current limiting circuit (shown below), that ...
4
votes
1answer
3k views

Current limiters using transistors and diodes

I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I started a question based on a conventional 2-transistor current ...
7
votes
3answers
2k views

Help needed optimising simple current limiting circuit

I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I have started using a circuit like the one found on this ...