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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1answer
38 views

Motor “load” for 8051 does not change based on 8051 GPIO pin

I implemented a circuit very similar to the following (original source: 8051 - Can an NPN transistor be driven? ) to control power to a vibration motor from my micro. I made the following ...
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3answers
106 views

Is it a good practice to use resistors for MCU inputs for this case?

I want to use Arduino Uno or a Nano which uses ATMEGA328P as micro-controller. D2 is now set as INPUT. During the start up I want the MCU to detect whether pin D2 is HIGH or LOW depending on the ...
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2answers
31 views

24V supply run 12V 3014 LED strip in series; help with resistors for series

i need help with wiring up some pieces of a 12V LED strip in series to run on a 24V 150mA supply. i want to add resistors , to help keep the strings evenly balanced. i don’t know if it is necessary, ...
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1answer
3k views

Why are all my yellow 2V/20mA LEDs burning out with 330k Ohm resistor?

I have a very basic circuit on a breadboard using an Arduino's 5V+Gnd to power a few LEDs. All the LEDs are from Sparkfun and rated at 2V/20mA, coming in Red, Green, and Yellow. I'm using 330 Ohm ...
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2answers
68 views

Resistance and wattage [closed]

I have a 6 Watt LED strip. When I turn it off it flickers briefly every 20 seconds or so. I placed a 20 Ohm, 1/4 Watt resistor in parallel across the connections to the LED strip and the flickering ...
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1answer
53 views

Mosfet Gate Resistor

I am building a high power ZVS induction heater. I originally used this famous design. It worked like a charm when I used a 48v 31A power supply. But I want an upgrade. I recently got a few of these ...
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33 views

High power source and low power load (device) [duplicate]

Can we drive low power load on high power source? For example we have source power 12 volt 60 amp and load power 12 volt 5 amp. Do we need resistor between them? If needed, what value will it be and ...
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1answer
41 views

Which wire should I use as dummy load for this specific PSU

I'd like to make lab power supply out of my old ATX Power supply. I am beginner in electrical engineering and this project seems pretty straightforward. I've checked many tutorials about it and ...
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2answers
95 views

Surface Mount Resistor Clip?

I have a goofy idea: a user is given a PCB and a pack of surface mount metal film resistors. To configure the board's settings, the user places various combinations of resistors into several 'sockets' ...
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1answer
67 views

What Resistor to use between Source and an IC

I'm trying to make a clock, and as part of that I need to power some IC's. To give a specific example I'm looking at the TI SN74HC163 4 bit counter. After some searching around, I found myself ...
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2answers
60 views

LED Circuit - Resistor calculation

If I have an LED such as this It has a forward current of 20mA It has a forward voltage of 2V. If my supply is 3.3v, am I correct in saying I would need a resistor value of 65 Ohms. My calculation ...
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3answers
78 views

Are these two equivalent [closed]

Are these two equivalent? Z is characteristic impedance of the transmission line and theta is electrical length of it.
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1answer
100 views

Controlling the current through multiple LEDs linearily and efficiently

I have around 100 infrared LEDs, each with an adjacent phototransistor to detect small differences in the distance of several objects (QRE1113). As the objects materials differ, I want to be able to ...
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1answer
45 views

Confused about proving series and parallel resistance equations

I am attempting to read through The Art of Electronics.In the early sections of The Art of Electronics the authors asks to prove the series and parallel equations. I am unsure where to start. I know ...
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0answers
61 views

Find the transfer function of an opamp circuit

I've the following circuit: simulate this circuit – Schematic created using CircuitLab I need to find the transfer function of this circuit. I did the following: $$V_+=\frac{R_1}{R_1+R_2}\...
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2answers
55 views

UCC28C42: TI simulated ,Resistor Heated

I am using an UCC28C42 in my circuit. I need a clarification of some resistor. I am converting 48V to 24V. If my load increases to 4.5A then Resistor is getting heated up.(Circled part) I used ...
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26 views

Step response of Series RLC circuit

Can we solve this question by using KVL to derive characteristic equation and passive sign convention at t>0 rather than using derived formule. p.s. the response I(t) is underdamped. I am having ...
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2answers
68 views

how to correctly power the LED of a push button?

So I've got a push button and a switch. Both of them have LEDs inside. Both of them seem to have LEDs working at 12V. But according to the specs of the push button, you could also use 6V. My ...
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1answer
47 views

Sense Resistor in Battery Charging Circuit

I have a 3 18650 in parallel Li-ion battery pack and wish to use the LTC4162 as the charger and LTC2944 and the level indicator. I am unsure as to who to wire them to effectively use both. I noticed ...
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1answer
27 views

feeding scaled down voltage to XADC (Xilinx)

simulate this circuit – Schematic created using CircuitLab I have XADC (Xilinx) with single ended voltage range of 0-1V. To regulate the output of a DC/DC converter let's say 15V i feed the ...
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1answer
89 views

Resistor and power supply [closed]

A 1.5kohm resistor has a power rating of 3.75W. if it is connected to a 24V power supply, will it be damaged? why?
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1answer
82 views

Do carbon resistors not follow tolerance as they age?

I'm trying to figure out the problem with my LCD and resistors. The micro I'm using is AT89S52 and the LCD is a standard display based on the HD44780 chipset. Part of the code in my micro allows for ...
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3answers
151 views

Why are THP 1/2W resistors bigger than 1/4W while 1206 resistors are all equal?

How come THM (through hole mounting) 1/2 W resistors are bigger than their 1/4 W or 1/8 W counterparts, while SMD 1206 1/2 W and 1/8 W resistors are equally sized?
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2answers
91 views

Maximum rating of resistor

I have a fusible resistor In some situation resistor will damaged. How can I calculate the maximum current a resistor can handle with a safe limit? is this resistor can handle inrush current from ...
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1answer
70 views

Trying to attach resistor to MacBook logic board (a1278, 820-3115-b)

On my logic board, I knocked off a loose resistor when I was replacing my battery. The resistor was r6700, which is located right at the edge of the board and its function is to detect headphones. So ...
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1answer
31 views

Voltage drop at gate of pmos (or nmos)

Sorry if this question has been asked before, I've tried looking through google and Stack Exchange and I can't seem to find the answer. Resistors on the gate (R3 on the picture) are usually in the K ...
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1answer
69 views

how to lower a power bank USB 5.1v /2.1amps output to 4.5v to power a 150 lumens LED flashlight [closed]

I would like to use a power bank to power a 150 lumens flashlight 3 AAA batteries operated ( https://www.harborfreight.com/ultra-bright-led-portable-worklightflashlight-64005.html ). I already ...
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2answers
83 views

Raspberry Pi Zero 12V Battery backup to 5V - do I need the resistor?

I found this diagram on the internet which seems to divide the voltage down to 5V and still be able to deliver 1A with the 7805 just like I want. It will use a 12V lead acid battery and a 12V IN ...
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1answer
78 views

Resistors scaling in voltage divider?

For my bench power supply, I am willing to make a voltage divider with two potentiometers (for coarse and fine tuning). I think I got the schematic right but what I am not sure about is the influence ...
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1answer
64 views

How do I measure the voltage across R3 (Va) in this circuit?

This circuit has been troubling me for a few hours, I've been able to measure Vout and the Thevenin Resistance, however, I haven't been able to calculate the voltage (Va). Any help would be ...
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1answer
30 views

Circuit thermal analysis in PSPICE and temperature coefficients

I am tying to perform a thermal analysis in pspice. Resistors needs two temperature coefficients as TC1 and TC2 (if we assume linear change of R vs. T, it's zero) in pspice. But in resistor datasheets ...
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0answers
37 views

LED Matrix creation using resistors & MAX7219

I've been attempting to create my own LED matrix, but now I've plugged it all together I'm getting some unexpected LED's lighting up, it seems some are getting power when they shouldn't (not very ...
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1answer
200 views

5 band resistor. Red, orange, black, gold and black. It doesn't fit in to normal rules

I have a difficulty in identifying a five band resistor. Color sequence is red, orange, black, gold, and black. It doesn't fit in to normal rules. Depending on the location of its use I expect that ...
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0answers
28 views

How can I measure voltage up to 120V in an Arduino? [duplicate]

I'm a beginner in electronics world, I've developed things before but not so sofisticated. Now I have to create a prototype and I need to measure voltages up to 120V. I've seen there are sensors that ...
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1answer
29 views

Pull down for 74HCTXX series logic ICs

I am building an adder with standard 74HC/HCT series logic ICs. I see the result when input pins are left floating are erroneous. Shall I have to connect some pull down resistors. Thank you.
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2answers
87 views

What is the use of these resistors in the schematic?

I am trying to build a line-following robot with the schematics I found below. I understood that the comparator is used as the logic for the robot and there is no need for a feedback loop for the ...
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1answer
82 views

Can someone identify this transistor and/or resistor component?

I stumbled upon a weird transistor or resistor component which I can't place. Here is a simplified version of the circuit: I am pretty sure that the transistor on the bottom is an N-MOS transistor ...
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0answers
48 views

(Inductor) Low-pass filter for current signal

I'm using resistors in a series circuit to vary the resistance between a constant 12V supply line and ground. Using transistors, the current either flow through all resistors, or is routed to ground ...
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2answers
123 views

Resistor getting hot - up to 50°C. Is it an issue of the resistor wattage or nature of the resistor?

I am using an FOD817DSD optoisolator. According to the datasheet: CTR: 300% - 600% @ 5 mA VF = 1.2 V (typical) @ If = 20 mA. We have 10 optoisolators on the PCB which is connected to some other ...
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1answer
67 views

Approximating a zener diode with an independent voltage source in series with a resistor

Given the following schema: The zener diode IV-relationship is actually a piecewise-linear approximation to a real diode. Having the following values: RIN = 1 kΩ RL = 2 kΩ VI = 9.5 V ...
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2answers
157 views

Does resistor placement change power dissipation in simple LED circuit?

Does the power dissipation in an LED and resistor change depending on the resistor placement? Let's assume the following: Supply Voltage: 3.3v (DC) LED Forward Voltage: 2.1v Resistor: 330 Ohm I ...
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5answers
136 views

Delay introduced by parallel R/C components

I have an envelope follower circuit which uses a LT1013 op-amp to multiply an audio signal to a logic level (~4.7V). Then the signal is filtered to create an output of the original signal’s envelope. ...
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1answer
63 views

Pull down resistor with 24v

What is a good value for a pull-down resistor, which when switched, connects to 24v? Is there a formula to derive this? This is effectively how it's drawn in the schematic (the inverter input's ...
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1answer
62 views

Identify the element among RLC

question : A two terminal network consists of one of the RLC elements . The element is connected to an a.c. supply .The current through the element is I A. When inductor is inserted in series between ...
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3answers
4k views

Is this resistor leaking? If so, is it a concern?

I found this resistor on the control board of an old Whirpool washing machine: Is that fluid leaking from the resistor? (Why would that happen?) Could it be something like stray epoxy or a chemical ...
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2answers
60 views

Stove element as a resistor

I am wanting to use an inverter based TIG welder as a constant current power source for anodizing aluminum. The main hurdle I suspect I will be facing is that the amperage of the welder may be ...
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0answers
69 views

How make a pulse acquisition from an electrical meter directly into a raspberry pi?

I would like to acquire pulse informations from a french electrical meter. There is a picture of the outputs of this electrical meter. These pulses vary in frequency and after acquisition, we can ...
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4answers
639 views

High resistance, no current. What's the point of a potential then?

I am referring to this example: Why does it matter that the IC has a high resistance? What does this do for/to the IC? If there is a potential but no current, what is the point of using the IC when ...
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2answers
90 views

Connect 10 LEDs using 5 volt current

I have 10 yellow-colored LEDs and ten 220 ohm resistors. I don't have any power source except the Arduino's 5 volt itself. Is it possible to power all the 10 LEDs using the 5 volt equally? Or will ...
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2answers
90 views

Design a Circuit with Zero-Order Transfer function H(s) > 1

I know that if I do 2 1K ohm resistors in series, I can just do a voltage divider to get Vout/Vin = R2/(R1+R2) = 0.5. But if I want to get a transfer function of 3, what components would I use?