# 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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### 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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### 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 ...
155 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. ...
394 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
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### 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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### 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 ...
1 vote
305 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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### Is a current limiting resistor needed for dual opamp supply pins?

Consider the TL072 dual op amp that is supplied with +/- 12V. The datasheet says that the supply current for (each) amplifier is typically 1.4 mA, with maximum of 2.5 mA. If both amplifiers are ...
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### Power Supply Module Internal Trimmer circuit / Remote Programming Resistor Value?

I am looking to incorporate a 45V supply into a design. These PFE1000-48V supplies have a trimming ability to get +/- 20%, based on +/- 20% variable resistor. I am trying to confirm what this resistor ...
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### Feedback resistor and capacitor calculation for transimpedance amplifier

I am designing a transimpedance amplifier using LTC6268-10 from Analog Devices. The photodiode that I use is S9055-01 from Hamamatsu and the laser source that I use has a power of 10mW with the ...
618 views

### 0 current in a circuit using tunnel diode

Suppose we have a diode with negative differential resistance of -40 ohm in the region of 0.3-0.5 V and we put it in parallel with a 40 ohm resistor: simulate this circuit – Schematic created ...
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### Need help lowering 5.5V to 3V for my GPIO input

So I'm new to electronics and sorry for the cursed images of circuits, but I have a background in computer science and trying to make this work. So I took the connection from my Intercom bell and it's ...
2k views

### Why do the leads of some resistors have holes?

Why do the leads of some resistors have holes? Is it to: Run a wire through it before soldering? If so, what is the best technique? Run a tiny screw through it for connecting a tiny lug? Provide a ...
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### Analog to digital conversion for neural network weights

I am a machine learning researcher, and lately I am getting interested in neural networks trained on analog hardware. However, I have some doubts about their potential, probably because I am missing ...
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### Are these trim potentiometer measurements expected? [closed]

I am trying to replace a 2-D analog joystick assembly that no longer works, because I dropped it. The assembly looks just like the one pictured in this forum post. My question is about the trim ...
1k views

### Tiny inductors and capacitors connected in parallel to a DC motor terminals

Why would you connect tiny resistors and capacitors in parallel to a DC motor as shown in the picture? Why would two of the resistors be connected to the outer shell of the motor? I checked the ...
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### Calculating optimal resistor values for an ATtiny84A circuit and NPN transistor vs MOSFET

I am starting my first project in electronics and I am having a hard time understanding the information available in the 84A's datasheet (pg. 179, Electrical Characteristics) While drawing the ...
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### Can I connect low-power resistors to achieve a high-power resistive load?

I've designed an 80 W 400 V PFC boost converter and I want to test it with resistive load. but I couldn't find a low-cost high power (20 to 80 watts) resistor in the range of 2k to 10k ohm. Is there ...
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### Voltage Based Current Limiting Application

I have a mobile application where I need to pre-charge the capacitors in a Victron 24v MultiPlus with a resistor before closing the circuit switch to its battery bank (24V 200Ah lithium); this ...
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### Find time in RC circut with known C and R

In a series RC circuit with a voltage source the Capacitance(15uF) and Resistanse(22.4ohm) is given. The time at which the Voltage across the resistor is same as the voltage across the capacitor is ...
2k views

### What is the reason to connect 4 resistors of the same value as 2s2p? (image)

There are 2 parallel branches, each has 2x 10R resistor. It seems to me that the resulting value will be 10R, but I can't wrap my head around why would someone do this if it is not meant to dissipate ...
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### Level shifting of a 3 state pin

I want to design a simple battery charger using MCP73831/2. This chip has a 3-State state pin according to the table below: I have a 3.3V MCU and I want to connect this pin to a GPIO. The MCU is not ...
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### Computing voltages over resistors [closed]

How do you use the combine/redraw method to find the voltages of the different resistors?
53 views

### PWM Controlled Resistance vs Resistor to minimize heat dissapation

I have a low-ohm resistor (7.5 ohms) connected to a MOSFET used for passive charge balancing. It is generating a lot of heat on my PCB. I can apply a duty cycle to the switching which somewhat combats ...
1 vote
104 views

### Parallel RC Circuit Time Constant

For a general RC circuit that looks like the following: (Sorry for the rough sketch of the circuit, I couldn't find a picture online) What would the time constant or RC equations be? My thinking: The ...
1 vote
76 views

### Load testing using a resistor bank

I have a bespoke 48V down converter that I'm looking to test which should be able to provide a maximum of 500W of power. I'm looking to test the device under various loads - from 50W to 500W. I'm ...
1 vote
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### Dependent voltage source in RL circuit

In this question, V1 is a dependent voltage source. The question asks us to calculate i(t) and ix(t). Assume that $i(0)= 10 A$ for the inductor. I decided to make mesh analysis. Mesh 1: 0.5\...
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### Measure Magnetic Field Circuit

I saw a design of a magnetic field meter circuit at here.This circuit looks like it can measure weak magnetic field such as earth's with only using inductor coil to gather magnetic field and without ...
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### Using resistor with 110 V LED indicator to make current measurement between 50 - 70 mA

I need your guidance with the V=IR formula. It's probably a simple question but I don't have an electrical background. I am working on making an LED simulator panel for railway signaling interlocking ...
352 views

### Measure Earth Magnetic Field using Hall Effect

This is about Hall Effect from this youtube video. The voltage across a metal will change based on the strength of the magnetic field. I am wondering whether this will be accurate in reading small ...
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### LED flasher circuit: unexpected behaviour

I am a beginner so bear with me. I have attempted to design an LED flasher circuit but it gives unexpected behaviour. Diagram: When I apply the 9V DC voltage, the LED stays on for about half a second ...
1 vote
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### What is the purpose of the 1 Mega-ohm 1/2 watt resistor between neutral and ground, in a vintage audio amplifier (SONY model STR-7800SD)

I own an old SONY radio / amplifier, model STR-7800SD. I opened it and I saw a resistor between one of the AC lines and the chassis. The funny thing is that it has a REVERSIBLE 2-prong plug! So, I ...
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### Diode and resistor in parallel

I was recently investigating a model of a circuit in which there is a resistor in parallel with a forward-biased diode. Why is the current passing through the resistor dictated solely by the forward ...
124 views

### Resistor bridging diagonal of square circuit

Consider a square ABCD where there is a one-ohm resistor on each side of the square. If there is also a one-ohm resistor bridging the AC diagonal, what is the equivalent resistance in ohms between ...
103 views

### Beautiful rain drop lights using multiple NE 555

This 74HC595 is used to create rain drop lights as shown in this Youtube video at here. Is there a way to replicate this using multiple NE 555 timers?
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### Shunt both op-amp input terminals individually

I'm working on a lab project for my class. My manual says that I need to shunt both OPAMP input terminals individually with resistors Rx = 1kΩ. I'm not sure what that means. Where should I put the ...
1 vote
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### How to accurately measure average temperature of a heating element?

Problem I'm trying to very accurately measure the heat of a nichrome wire as current is passed through it. My approach thus far has been to monitor current and voltage across the heating element and ...
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### Mysterious Component Marking

I have stumbled across this component which I’m trying to replace. It has a rating of ‘22mOhmF’. It looks to be a resistor but I am confused as to why there is a ‘F’ in the rating as this indicates a ...
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### How do I use a microcontroller and transistor to control resistance on a wire?

I need to programmatically pull a wire down to ground with a 1k resistor. I put the following schematic together on a breadboard and then programmed a GPIO pin on a STM32 microcontroller to alternate ...
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### Custom LED light bulb protection /

I wanted to design a custom LED light bulb, so I bought a couple and tore them down in the hope to reverse engineer them. Most of them implement a circuit with a chip shown as below, with the circuit ...
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### Issues with getting UR

I'm trying to get UR5 from this schema, but something is not right. All I have so far
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### Building DC to DC converter using a inductor

Can I build a DC to DC converter like this? simulate this circuit – Schematic created using CircuitLab When the switch is moved due to the low resistance path it will take a lot of time for the ...
1 vote
125 views

### Resistance averaging circuit / resistance divider circuit (NOT voltage divider)

I'm trying to design a circuit to average 3 Pt100 resistors to feed into a single temperature controller. All the solutions I've found so far involve either a microcontroller or a complex opamp + ...
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### Half-bridge IR 2184 discrete component

I found datasheet for IR2184 HALF-BRIDGE DRIVER IC here . I was hoping to find the IC discrete components circuit from which it was built upon using transistors, diodes, resistor only but its not in ...
202 views

### Voltage divider formula?

Actually I am not able to understand how the author arrived at this equation using voltage divider formula ? what I tried is , I combined the two 2R resistor connected to ground in series and wrote ...
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### Typical inductance of power (probably wound) resistor

I need a big resistor to dump reactive energy to. But I need it 'fast' since otherwise the input TVS will overload. The situation: parasitic inductance of wiring makes the whole circuit substantially ...
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### How can I limit input current to a raspberry Pi to 2 amps from a high current battery?

The circuit I currently have consists of a motor circuit and a raspberry pi circuit connected to the same battery. (2 series circuits from the same battery). The problem is that during idle motor, a ...
63 views

### How many times larger should the gate resistors be than the drain resistor?

I was asked this question in class and could not come to a concise answer. This is question was asked in terms of MOSFET design. Are there any general rules or guidelines to follow?