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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19 views

To evaluate equivalent resistance of the circuit by star delta method

How do I evaluate this circuit via star delta method?
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21 views

Home made birthday gifts using Electronic components

Friends I want to make a birthday gift for my sister using basic electronic components like transistor, resistor, capacitor. Last year I made a gift like this for my sister. This year also I want to ...
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34 views

Serpentine PCB heater size calculation

So, I'm kinda new to the field and the time has come to design my first PCB heater. The main concept is to drive it using a Raspberry Pi and a temperature sensor as feedback. Here is the whole ...
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50 views

How to limit maximum voltage when it's 0.1V too high and the device controller complains?

I built a retrofit Li-Ion battery pack for a scooter that originally ran on two 12V SLA batteries in series. I measured the voltage of the original SLA charger during the CV phase and it measured 29....
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83 views

How will I know the power [dissipation] of resistor when buying resistors?

It is very basic question for many people. It is very easy to predict the resistance of a resistor with multimeter, but sometimes it comes with resistors which are slightly larger in size, such as, ...
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24 views

Low pass filter for DC Battery charging as well as on inverter mode

i want add a Low pass filter between battery and 720watt ups inverter. because dc charging wires has some ripple voltage. I want to make it pure dc... charging voltage is max. 14.4vdc and charging ...
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63 views

How to power a device using a USB port instead of AA batteries?

I have a device that uses 3 AA batteries and I would like to power it from a USB port instead. As I understand I will have to use resistors but I have no idea on which ones. I have found the ...
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1answer
57 views

Unknown equation in the SPICE resistor model

I was looking for simple resistor spice model, and came across this: ...
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2answers
115 views

I cannot find resistor in the market

I'm trying to replicate this design and I cannot find the 6K/1% resistor in any online store (Digikey, Mouser). What can I do? the design I'm trying to replicate is this As per @Huisman request, all ...
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52 views

Car Battery Charge Indicator Replaced with LED then Dimly Lit When Off

I think I should be able to grasp something from this question but I'm not sure if my case is the same or not. Would be great if I can get enlightment on this. In my case I'm replacing incandescent ...
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97 views

Can resistive traces be created on a PCB?

I'm assuming that copper traces on a PCB have negligible resistance. Is it possible to put a trace on a PCB that has some greater amount of resistance? The amount of resistance would not need to be ...
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29 views

Is this circuit for Piezo Transducer and corresponding resistor values correct?

I want to drive this piezo transducer (https://www.mouser.com/datasheet/2/670/cpt-9019s-smt-1310960.pdf) at 3V and 4kHz with STM32F0 microcontroller. This is a follow-up to my previous question (Is ...
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26 views

Building DIY TrackIR, need wiring help

I'm attempting to build a homemade head tacking unit for use in computer games using infrared LEDs for my kid. I followed one tutorial where they were wired in parallel. After doing more research, I ...
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94 views

A 4(5)-band resistor with an extra black band

I need to replace a burned resistor in an electric kettle, but I'm not sure I identified it correctly. The bands are: Red - Grey - Grey - Gold - Black. My preliminary guess 28.8 Ohms no tolerance. ...
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51 views

Half H-Bridge Control

I need to control a Half H-Bridge circuit to move a DC motor on both clkwise and ctrclkwise directions. I've tested the following circuit: It worked as it was supposed to: when the digital input ...
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3answers
127 views

Can I increase the power rating of a film resistor if I increase the cooling?

I am trying to apply 1 kW of heat to an area of 10x10 mm and I am considering using a panel mounted film resistor. One that meets my power requirements doesn't exist so I am wondering if I can go ...
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80 views

Confirming resistor value

Hi I need to replace this resistor but I am not convinced that I have read it correctly at 180m ohm. Can someone confirm please? The third band looks like pink but I ha w read it as violet.
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56 views

What is value for r2 and r3 in circuit for 100f supercapacitor

What is resistant value of R2 and R3 of 100f supercapacitor. And what is the gain/beta. Value of op-amp in this circuit. simulate this circuit – Schematic created using CircuitLab Schematic ...
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Is there a method to find how to combine resistors in order to get a specific resistance? [duplicate]

I was working on this homework: Using only 1k resistors, synthesize a resistor of 3/5k and a resistor of 5/3k. Use no more than four 1k resistors in each case. I found how to do it but I'm not ...
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73 views

Why is voltage across LED filament bulb slowly decreasing?

I'm trying to power this LED filament bulb with a 12V - 2A DC wall adapter. LED specs: rated at 4W 12 to 24V input I'm pretty new to this, but if I get it right: Calculus the LED bulb will draw ...
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62 views

Determine the resistor required for a circuit

If I want to supply power to a device that is rated for about 2V using a DC source of 12V. How can I find the resistor o should use.
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1answer
57 views

Is it possible to control a PWM computer fan with a resistor? If yes, how? [closed]

I have a video card that is loud while idle, because the fan curve appears to be set rather aggressively. Unfortunately, this can not be changed via software. The fan is connected with a regular 4-...
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36 views

Transimpedance AMP, Active HPF, phototdiode (updated)

The original post is here Transimpedance AMP, Active HPF, phototransistor I decided to change back to a photodiode instead of a phototransistor since I have used one for a similar experiment in the ...
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108 views

Why is there a resistor between the primary and the secondary winding?

I recently opened up a linear power supply and found out it has a resistor of 8.2M ohm between the primary winding (specifically in the neutral) and the secondary winding of the step-down transformer. ...
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36 views

Voltage gradient in voltage difference across a resistor

If I have a voltage difference V from terminal 1 to terminal 2 of a resistor. I take an arbitrary point P along the resistor, between terminal 1 and terminal 2, and take terminal 1 as a voltage ...
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106 views

Why does the measured current differ from the calculated current in this circuit?

I have the following schematic: Now I want to know the (more or less) exact current flow in my circuit. For this I did the following calculations: I = V / R I = 5V / 330 Ohm I = 0.015A = 15mA So ...
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Novice LED questions

I'm hoping that you friendly and knowledgeable folk can help me finally figure out how I should be wiring up my LEDs in my panels. Just a short history... Many years ago I took over a panel building ...
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45 views

NPN LED variable resistor

I am still beginner to design and so I would to confirm that the variable resistor setup is correct? I have an LED that operates at 2.7V with 100mA so I added a 23 Ohm resistor. Vcc provides 5V and ...
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103 views

What is the value of this 5-band resistor

The colors are black, light green, green, red and silver (looks more like gray). I am not sure which side to start reading the values from. Both ends seem to be symmetrical. Moreover, I have never ...
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53 views

Electrical RL circuit problem

So I am given u(t)=325sin(314t+90°)V i(t)=14.14sin(314t+30°)A I have to find the impedance Z∠θ, value for the resistor and inductor, inductive reactance Urms∠θ = 325/sqrt2 ∠90° Irms∠θ = 14.14/...
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91 views

Using a resistor on one branch of a parallel circuit affects the other branch?

I've wired in one doorbell button to an 18v AC PSU which is working fine, but upon adding a second to the circuit it didn't work properly. I found later that the second type of doorbell needs a '25 ...
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80 views

Resistor for high power but low energy (pulsed operation)

I need to make a pi attenuator which must support voltages of about 100 V and 20A but only on a pulse of 250ns. But I do not know what resistor to use because it creates a power of about 2kW but only ...
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73 views

Selecting a damping resistor for crystal oscillator circuit

I'm building a data acquisition board with an ADAR7251 ADC. I'm trying to figure out the crystal oscillator circuit, and am stuck on the damping resistor. The relevant datasheet is https://www.analog....
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Why is the battery jumpered to a resistor in this schematic?

I am looking at a schematic for the wifi D1 mini data logger shield that I'm using right now. In this part of the schematic, a coin cell battery powers the RTC. I see R5 is jumpered across the ...
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1answer
76 views

LED strip keeps blowing transistor

I made two LED controllers using an ESP. On the PCB I'm using three 2N2222 transistors + resistor (1k Ohm) at the base to control the 12V circuit powering the LED strips by applying 3.3V from the ESP. ...
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10k views

Weird resistor with dots around it on the schematic

I was looking through the LTC4041 datasheet and saw this: The 10mOhm resistor with the two nodes really close to it - is that a "special" resistor or something? Why have they drawn it like that?
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Will using a resistor in series with a LED to control its voltage increase the total energy expenditure? [duplicate]

This might sound like a stupid question, but I want a confirmation. I watched a video on Youtube about using LEDs. Those LEDs required a voltage around 2 volts at 20 mA. In order to power one LED ...
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1answer
32 views

Non contact AC voltage detector resistors

In this non-contact AC voltage detector, I understand the working principle of taking a tiny induced current in the antenna and amplifying it using transistors. However, I do not understand why the ...
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74 views

Reading an optocoupler datasheet and calculating the resistors for its input/output

This is a continuation from this question (sort of) I want to replace the relays from an existing circuit with optocouplers and had trouble how to read the optocoupler datasheets as well as ...
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949 views

Voltage across a resistor

We have a voltage source of 5 V and a resistor of 100 Ω is connected to it. The other end of the resistor is connected nowhere. To simplify terminal “A” of resistor is connected to 5 V & Terminal “...
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1k views

What difference between two discharge resistors in two circuits?

When I search for 220VAC led indicator, I found two circuits one from here circuit 1 another here circuit 2 The purpose of R1 from two circuits for discharge C1 when main AC off, but is there any ...
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LCD Dimmer with Variable Resistance Circuit

essentially I'm trying to make a very basic circuit where a 3.7 volt battery is wired to a liquid crystal display, (or LCD), and the brightness of said display is controlled by a pentiometer to ...
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52 views

How to choose resistors in a decade counter circuit?

I'll start off by stating that I am a novice. I'm trying to figure out how to use a decade counter, so I've constructed this circuit: It worked fine, but now I'm wondering how it was decided to ...
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55 views

Current Sense Resistor Layout

For a current sense resistor, should I connect the high current terminals to the current sense terminals as shown in the picture?
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43 views

How to reduce the speed of this motor?

I have an old Siemens motor with this specification : 220V 80W 0.65A I need to reduce the speed (slow down) of this motor. I know it's easy with something like an inverter, but I'm just wondering ...
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91 views

Reducing 3v supply to run 2.4v laser diode

I am setting up a laser trip wire system, this question revolves solely around the laser itself. IMPORTANT: The laser is always on (it will have an on/off switch) Supply voltage is 3v (2x aa's) ...
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98 views

Parallel Incandescent Bulbs and Resistors

I have built the circuit in LEDs and high currents and it works well - when the switch is open, the incandescent lamp lights up but the LED doesn't. When the switch is closed, the lamp goes out and ...
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53 views

Best conductive ink mixture for potentiometers

Im 3d printing a model for a 2 axis potentiometer, and I need a carbon ink mixture that will hold up to the copper wiper, and produce around 10kOhm resistance in a line around 1mm*6mm. Searching ...
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1answer
49 views

What resistors do I need for a simple LDR triggered h-bridge?

I am attempting to build this circuit: https://www.instructables.com/id/H-Bridge-on-a-Breadboard/ But instead of switches, I want ldr s like this circuit: https://www.instructables.com/id/Simple-...
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2answers
124 views

Question about the accuracy of integrated resistors

I'm studying the implementation of resistors in integrated technology. In particular the books deals with the accuracy of the obtained resistors. It says: Then it says: "We observe that the value of ...