Questions tagged [resistors]

A resistor obeys Ohm's law (V=IR); the current through it is equal to the voltage across it divided by the resistance (equivalently \$I=\frac{V}{R}\$)

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How to infer resistor size from the manual of this microcontroller board?

I have STM32's NUCLEO-F302R8 board. The manual is given here. I couldn't find any PCB design file for this board so that I can open it in KiCad, Eagle,etc.. From the manual I couldn't figure out the ...
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Convert speaker level to microphone level

I have a digital piano without line output (not even earphone output) but I would like to record what I am playing. So I decided to convert the speaker level to mic level so I can record the audio in ...
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1 vote
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Why are there two NOT gates in a complementary PWM circuit?

The above is quoted from here. What is the purpose behind two NOT gates? Why not just attach a wire across it since two NOT gates will neutralize each other? For example, 1 will output a 0 for 1 NOT ...
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finding replacement for resistor labeled as fuse in schematic

I am trying to find a replacement for what appears to be a burned resistor in a power supply unit. It appears to be labeled as "F3" on the PCB which is the designation for a fuse. As far as ...
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Can't find formula to calculate resistor values for a BQ34Z100

I am designing a BMS board using the BQ34Z10 fuel gauge IC. From the datasheet BQ34Z100 datasheet figure 8-3 I am unable to figure out how to calculate values for R2,R3,R4. I am designing the system ...
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In a DC voltage sensing circuit, what's the need for capacitors on input and output?

This circuit uses a voltage divider to lower the voltage, and then uses an op-amp as a buffer (with some gain). If the input signal is always DC, why do I need these capacitors? The way I understand ...
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SPI MISO line not working

I am using a KSZ8463 Ethernet Switch IC. When I connect the SPI MISO lane to another board having 2 peripherals - CPU and a CAN Controller IC - there's a spike of 0.3A current and the Switch IC stops ...
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Which electronic circuit simulator is working wrong?

I ran a simulation of the same circuit on three simulators and one gave me different values. Which simulator working right and which wrong? Falstad: EveryCircuit: PartSim:
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3 answers
436 views

Why does the voltage not change when the resistance of the resistor changes?

Why does the voltage not change when the resistance of the resistor changes? Why the voltage after the resistor always 0V? I am new to electronics and don't understand it.
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Resistor array datasheet

I'm looking at the resistor array with specifications Temperature Coefficient of Resistance ±100 ppm/°C; TCR Tracking 50 ppm/°C maximum Does that mean that they are resistors with ±100 ppm/°C with ...
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Resistor surge current rating: Why is the pulse energy withstand capability lower for short duration?

As per an online surge capability calculator, the pulse energy withstand capability is low initially and increases with higher pulse width. In short, we are not allowed to pass a narrow high current ...
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Which resistor/solution should I use?

I have (had) an UPS which got wrecked during flight, I disassembled it and found something broken. I don't really know which resistor should I install or how could I fix it. The other resistors are ...
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1 answer
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What will be the equivalent resistance in this situation?

We have to find the equivalent resistance between A and B. My attempt: Let's simplify the circuit. simulate this circuit – Schematic created using CircuitLab Now, $$\frac{1}{R_P}=\frac{1}{5+5}+\...
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2 answers
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Astable multivibrator small capacitor values

Is there a method to determine the values for the resistances? below shows when R1=R2 << R2=R3 and the capacitance is 10uF and the circuit works perfectly. However if I try to reduce the ...
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-1 votes
1 answer
60 views

Negative resistance - crystal

Why do we have the negative resistance concept in a crystal? How does the crystal exhibit negative resistance? I've read this Link and it seems to say that the amplifier is the one that causes the ...
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What conditions can cause a PCB fuse to fail and act as a resistor?

Context: Tx circuit that shoots 24V pulses into a transformer to get 240V out of it. The purpose is to drive a piezoelectric transducer. The circuit itself has a fuse protecting it at the entrance (...
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-1 votes
1 answer
40 views

Effective resistance integrator circuit

I've encountered the following circuit and I'm puzzled about the effective resistance that the opamp will see. I know that R1 is in parallel with R2+R3, so this would be easily answered by R1*(R2+R3)/...
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Nichrome strip and resistor

I'm trying to build a heater connected to 220 VAC, 50 Hz using a nichrome strip (2.3 Ω/m) and I'm going to use 1 meter or less (60 to 70 cm). I know that this setup won't work at all with 220 VAC so ...
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How to use dependent source in Proteus?

I am trying to determine the voltage at v1, v2 and v3 in a circuit like below using Proteus. ...
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4 votes
3 answers
136 views

What does a pull-up or pull-down resistor actually "pull"

What does a pull-up or pull-down resistor actually "pull"? What does "floating" value mean? What is "floating"? Eg. in this picture, if there is no 10K resistor then the ...
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2 answers
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Crystal oscillator - Gain

I was reading more about the crystal oscillators and had this question in mind. During the initial start up, the gain of the oscillator should be large and later on, the gain should be greater or ...
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Why is resistor temperature coefficient given in a +/- number?

For a given resistor you might see a TCR of +/-25ppm/C, but I'm not sure I quite understand that number. As far as I know, a PTC resistor like a basic thick film always increases in resistance as ...
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2 answers
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Line level to microphone level to record

I have a digital piano with an earphone output where I can connect a simple earphone (like in the picture below.) It works fine. I would like to connect this earphone output to my smartphone jack (...
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1 answer
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Power Rating of a HV resistor

I am conducting a project to measure Breakdown Voltage and would like to use a protection resistor, please see below. When breakdown happens I will have something like In this case the Power ...
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1 answer
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Do I need a current limiting resistor with an industrial rail DIN optocoupler?

I'm going to use this industrial opto-coupler: Optocoupleur RS PRO, montage Rail DIN, 6 mA In its specs document they don't mention the need of a current limiting resistor. I always add a current ...
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What happens if a ceramic power resistor is heated well past its rating?

What would likely happen if a ceramic power resistor was powered well over its power rating (for test/learning purposes and likely buried inside a bucket of sand)? By "well over", I mean 10 ...
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Activate arc lighter with Arduino

I have a SaberLight plasma arc lighter, and I have taken it apart for a flamethrower project. I would like to use an Arduino Uno to programmatically activate the arc lighter. Using the Arduino Uno, ...
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15 votes
2 answers
1k views

Which way to read this five band resistor?

Sorry for this basic question. I have a problem determining which way I should read band on the resistor below. I know it's left to right, but which side of it really is "left"? As far as I ...
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1 answer
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Can I use lower wattage resistor if I’m using a high voltage power supply?

I can use a higher gauge wire with the same wattage if I use a higher voltage so the current is lower. Can I do the same with resistors? I have a neon sign transformer that’s 450 watts at 15 kV and 30 ...
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2 answers
66 views

Will a resistor reduce voltage without current flow?

I asked a question where I was trying to figure out how my truck controls the speed of its blower motor. This answer provided the following diagram showing that it uses a set of resistors in series to ...
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6 answers
193 views

How to reduce power drawn by a resistor heater?

I am rather new in this field. On 220V AC industrial power supply, a 6 ohm resistor heater (nichrome wire, 0.40 ohm/m, 15 m) will draw about 8067 watt of power. About 2400 W are needed. What are the ...
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1 answer
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Finding the "drop in potential" as current moves through a single resistor of a circuit with parallel resistors

I have four different resistors connected in parallel to a \$24.0 \ \text{V}\$ battery with internal resistance of \$0.500 \ \Omega\$. The resistor values are \$10.0 \ \Omega\$,\$15.0 \ \Omega\$, \$30....
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1 answer
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Using a potentiometer to shift between negative outputs from either -2V and 2V

The question that I am wanting to ask is that I start off with either 5V or -5V which is reduced to -2V or 2V for my output for the potentiometer. My potentiometer has a 5k resistance and I am trying ...
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4 votes
2 answers
957 views

Why is capacitor discharge time higher when an LED is included?

I'm testing the discharge time of a capacitor. I found that the time is higher when an LED is present. Circuit with a capacitance of 100mF, 10k resistance and 5V voltage. By calculating discharge ...
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6 votes
1 answer
197 views

XKCD 356 puzzle

I was reading XKCD and saw this comic: Turns out it works, and have been thinking about this for an hour and have gotten nowhere. My first thought was to find the resistance of all paths of length ...
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1 vote
2 answers
47 views

Finding the voltage available at the terminals of the battery in a circuit with parallel resistors

I have four different resistors connected in parallel to a \$24.0 \ \text{V}\$ battery with internal resistance of \$0.500 \ \Omega\$. The resistor values are \$10.0 \ \Omega\$,\$15.0 \ \Omega\$, \$30....
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1 vote
1 answer
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Finding resistance for parallel resistors: how is my reasoning incorrect, and what is the correct reasoning?

I have the following circuit: The voltmeter \$V_1\$ measures the voltage drop across the \$9.00 \ \Omega\$ resistor and has a reading of \$4.50 \ \text{V}\$. The reading on ammeter \$A_1\$ is \$I_1 =...
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1 vote
3 answers
124 views

What limits the heating power output of a resistor heater?

I'm a bit confused since people said those resistors would draw more power the lower its resistance is, and one way to reduce its resistance is reduce its length. Will it draw more power the shorter ...
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What wattage should the resistors or pots be in a car audio voltage divider?

My new radio amplifies the output too much and my car stock amplifier is non-adjustable. The only solution (that I know) besides putting the stock stereo back in, is 4 voltage dividers. I'd like to ...
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Should I use a resistor in series when connecting a pin to logic level high?

I'm trying to design a circuit with MAX8934AETI+. I'm confused about how to connect a pin to logic level high. For example, pin 6 in the picture below is meant to be connected to logic level high to ...
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-2 votes
2 answers
80 views

How to use resistors to lower voltage? [closed]

I want to use a resistor to lower 3V to 1.8V but I'm not sure which one to use. How do I decide which one I should use?
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3 answers
39 views

What is the tradeoff in decreasing the frequency bandwidth when reducing noise of a resistor?

A resistor's Johnson (Inherent) noise can be modelled as an RMS voltage in series with the resistor: $$ e_{rms}\triangleq\sqrt{4kRT\Delta f} $$ where k is Boltzmann's constant, R is resistance, T is ...
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3 votes
3 answers
130 views

Driving a LED with a potentiometer in parallel, electronic basics

Today, in class, we were to analyze this circuit: simulate this circuit – Schematic created using CircuitLab And calculate \$\alpha \in [0, 1]\$ associated with R2 a potentiometer. I'm confused ...
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3 answers
117 views

Resistance measured individually vs measured on PCB

I always wanted to ask this question. Suppose I have a 1kohm resistor. I measure its resistance by connection a multimeter to both of its terminals (when it is not connected to any part of a circuit.) ...
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3 votes
1 answer
109 views

Which temperature sensitive material would be a good choice for temperature measurement from 4K to 300K?

I am building a thermometer for a cryostat which operates at low temperatures (until 4 kelvin). I would like to know the temperature of some parts in my cryostat during the cooling (so from 300 K to 4 ...
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2 votes
4 answers
154 views

How can I best reduce the current drawn by a PCB heatbed?

I have a noob question about fairly basic circuit design (I think). I am building an incubator for making Tempeh at home, and want to use an old PCB heatbed I have lying around as the heating element. ...
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6 votes
2 answers
390 views

Selecting series resistor for a Zener diode

I am currently designing a device that will be powered by eight AA disposable batteries. For reverse polarity protection I am looking to use a P-channel MOSFET in the following configuration: ...
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1 vote
2 answers
321 views

Can the connection of collector and base in these circuits be considered as a diode connected transistor?

I was learning how to design an op amp and I saw something thatis called "diode connected transistor." Like this image: Later I saw a person that was teaching about these circuits, and he ...
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2 answers
318 views

How to find the voltage on each of the parallel resistors? [duplicate]

Suppose we have a circuit like this: It is easy to find the voltage on the node shared by the two parallel resistors, we simply have to find their equivalent resistance and use KVL. But the problem ...
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1 vote
6 answers
277 views

RC time delay circuit to trigger relay

I'm trying to design a circuit that uses a momentary switch/push button to turn on an LED, then it turns off after 1 sec if the switch is held in the ON position longer than that. Below is a diagram ...
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