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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4answers
2k views

Why split the resistance on either side of an LED?

In the circuit below, is there any reason why we can't combine R1 and R2 into one 4 kΩ resistor in either location? simulate this circuit – Schematic created using CircuitLab I am reverse ...
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3answers
52 views

Why does the dynamic error of a low pass filter decrease when adding a load at the output?

I have this anti-aliasing low pass filter where R = 100Ω and C = 3.62μF. When the input has a frequency of 50Hz, Vin(t) = sin(2π*50t), I have worked out the dynamic error and found that the maximum ...
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2answers
327 views

LED with built-in resistor and voltage drop

I accidentally bought 12 V LEDs, so an LED with a built-in resistor (you can see it as a black dot on the anode). Now I measured the voltage and get after the LED still a voltage of 11.3 V, when the ...
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0answers
54 views

How badly is this damaged? [closed]

Last night I ran my loadbox from my guitar amp, and it start to smell badly. I may have overcharged the power out to the loadbox. I decided to open the box and look for any visual damage. I saw three ...
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4answers
130 views

Powering a 1 watt LED using a 3 V coin cell

I was hoping to power a 1 watt LED (would be great if this is capable of powering 2 or 3 watt LEDs) with a 3 volt coin cell. Will the coin cell be able to output voltages and amperages that are ...
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0answers
46 views

Coil fires at 0.6 ohms. Ignition triggers at 3.0 ohms. Can I add resistor to hold coil back to 3.0 ohms?

Can I add resistor to hold 0.6 ohm coil back to 3.0 ohms which is when my ignition triggers. Harley Davidson.
6
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9answers
2k views

What is the correct supply voltage for LEDs?

I have a 5V supply power, three 5mm red LEDs, and each LED has 47-ohm resistor. Two LEDs are bright but soon as I connect the third one all of them become dim. Where am I going wrong? I'm new so a ...
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1answer
53 views

1 resistor for all LEDs or 1 for each? [duplicate]

I heard that using a resistor for each LED in parallel is good, and I also watched a video on youtube. The guy said if your LEDs are the same type and color you can use just 1 resistor. Is there a ...
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1answer
37 views

DHT11 temperature and humidity pull up resistor

I am setting up my Arduino Due with the DHT11 temperature and humidity sensor. Most diagrams mention using a 10k ohm sensor. Is it OK to use a 5.1k ohm as that's what I have available?
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2answers
91 views

Can I use a resistor with higher resistance?

I'm very new to electronics and wanted to use a couple of led diodes, I used an online calculator and it says I need a 40-ohm resistor, my question is can I use a 100-ohm resistor instead of 50? what ...
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2answers
63 views

Measuring voltage drop across 10 ohm, 100 ohm and 10 kilohm resistors (one at a time) - very simple circuit

Below is a picture of my very simple circuit. There are three resistors 10 ohm, 100 ohm, and 10 kilohm. I connect them one at a time in serial fashion and measure voltage drop across them. When I ...
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2answers
103 views

LED open and short detection

Can someone tell me on what how to detect a short circuit and LED open circuit for the below circuit? Is it possible to detect which LED? Could someone provide a circuit which would help to detect an ...
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0answers
44 views

Capacitor Lifetime

Can anyone some sample calculation on how to calculate the lifetime on an Aluminum Electrolytic capacitor who's Endurance value (Assumed as Lifetime value is 2000 hours at 105degC). The manufacturer ...
2
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1answer
55 views

How do i control a 6 V supply output based on a 5 V input?

I have a signal from a microcontroller that varies from 0 V to 5 V. I also have a separate 6 V supply to power a motor. I'm trying to design a circuit that allows the microcontroller signal to ...
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2answers
50 views

Resistor with silver third band

This resistor, from the AC side of a power supply board, has a silver third ring and a white fifth ring. I've never seen such component before : It reads between 8 and 12 ohms on the multimeter and ...
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2answers
69 views

Resistor values for a non-inverting op-amp with gain of 2

I'm trying to build a circuit that uses a non-inverting op-amp to double the voltage in the circuit. The op amp I'm planning on using is: http://www.farnell.com/datasheets/2258629.pdf , and I think it ...
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1answer
37 views

Why does the current enter the negative terminal of this element and it is still absorbing power?

Hi there, I am learning the kirchhoffs-laws, according to the passive sign convention if a positive current enter through the positive terminal of an element and exits out of its negative terminal, ...
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1answer
68 views

First order RL circuit question

I have this circuit: simulate this circuit – Schematic created using CircuitLab At time t=0 we open the switch and IL = 0.At t<0 IL = 2.5A (What I mean by" At time t=0 we open the ...
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4answers
61 views

Recycling a flashlight

I am "another one of those" :) with some understanding but lacking knowledge. I can identify components, know what they are for and even change them when they are visually burn or broken. So ...
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4answers
176 views

Why are resistors classed as 'conflict' goods?

Further to a linked answer for Why recommend tantalum over ceramic capacitor for voltage regulator? , we have this:- Why is the resistor in the middle a conflict resistor? Should I stop buying un-...
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2answers
49 views

Phase shift in AC Circuit power calculation

I have the below question. I am not trying to ask the answer for the problem. But my question is that, we can see that 60deg is the phase shift. But both the voltage and current across the passive ...
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1answer
52 views

How to find the voltage at the circled node

I have this circuit. The voltage source is 4V and the current source is 2A with the 2ohm resistance. I got the node voltage at the circled node to be +8V from a circuit simulator. Can someone help me ...
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2answers
95 views

Water detector with a BC547 and help understanding transistors

I have set up a basic water detection sensor using a BC547 transistor to switch on an LED if there is current between two electrodes (which are spaced about 1 cm apart): I'm trying to understand more ...
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6answers
3k views

What is the purpose of the emitter resistor in a common emitter amplifier?

I'm struggling to understand the purpose of the resistor circled in red, I know it has something to do with DC biasing and the feedback on the circuit (as the capacitor will cause AC bypass). But I'm ...
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3answers
94 views

Voltage of capacitors after long time (RC Circuit)

I'm currently taking a course in electromagnetism, and I got stuck with this problem: The Problem: All of the resistors and capacitors have the same values, R and C respectively. The circuit is ...
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2answers
2k views

Resistor in shunt regulator not following Ohm's law?

I was reverse engineering a power tool battery charger (21V SMPS) that derives its 5V rail from a simple shunt regulator, employing a TL431 programmable precision reference and a NPN transistor, as ...
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3answers
90 views

Need help finding a proper replacement for a burnt resistor

I need to replace a burnt resistor, but I have trouble finding a proper replacement. The dead resistor has 5 color bands on it: ...
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2answers
69 views

How do I solve the equivalent resistance of this circuit?

How do I determine the equivalent resistance of the circuit looking into terminals A and B? I am quite stuck and the only thing I've figured out is that there are 3 pairs of parallel resistors: 90&...
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2answers
52 views

Why is the 2.2k resistor needed in an MT3608 module?

I am trying to implement an MT3608 module on my PCB. I went through its schematic which clearly describes the module. I see they have used 2.2k ohm resistor in addition to a potentiometer. From what I ...
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2answers
66 views

How to choose a perfect resistor to LEDs to get same brightness?

I'm using 5 different LED to indicate water level. I used a 330ohm resistor to all LEDs. Some LEDs glow brighter some are less bright. How can I calculate an exact resistor value to my LEDs to get ...
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1answer
29 views

ESP32 and moisture sensor transistor switch

I'm doing the classic water moisture sensor project with my ESP32, but I want to be able to switch the sensor on and off since that will reduce the amount of corrosion that occurs. Can I use a BC547 ...
0
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1answer
69 views

Fundamental similarity between resistor, capacitor, and inductors?

I notice that resistors, capacitors, and inductors share some fundamental similarities: for example, the way you compute their values in series and in parallel is extremely similar. Likewise, it seems ...
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1answer
60 views

Driving multiple LEDs from microcontroller pin

I have a 12 V supply and I want to connect 4 LEDs to each pin of the microcontroller. Voltage and current of each LED is 2.5 V and 20 mA. When the output of the microcontroller becomes high the LEDs ...
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1answer
128 views

Surprise resistors found in old voltage divider

I'm a grad student in physics that hasn't looked at circuits since early in my undergrad. I was recently handed a voltage divider that my group used to bias a micro-channel plate detector stack as I'...
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2answers
79 views

Limit current to a load

I'm making a little heated greenhouse. I have three 1.2 ohm 5W resistors and a 5V 1A power supply. Everything is controlled by my Arduino through a MOSFET. Now, I would just need 5W of power to keep ...
0
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2answers
48 views

What will be the output voltage graph of the following circuit if output voltage is considered across the resister?

The circuit is given below. I know that until the Vin reaches the first peak, the voltage across R (output voltage) will be 0 since capacitors draw current to charge. After that, I couldn't figure it ...
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0answers
32 views

Trouble understanding the LM555 schematic for 50% duty cycle oscillator mode

I am working with a LM555CN and I am trying to have it run in astable mode and make a LED blink. In essence I am trying to follow along with this video. Now, there is a part in the chip instructions ...
0
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1answer
100 views

Is there any way to have a diode that have very small resistance from reverse path?

I'm trying to find a way so I will always have close to 0V at the measurement point (above the diode), when I have 0V as input. ...
0
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1answer
43 views

Does this require a larger series resistor?

I am connecting a switch to an input pin on a Nexys A7-100T FPGA development board, like shown in the below image: The circuit has a 10K pull down resistor (R1 on drawing above) to ground and the ...
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1answer
45 views

How to calculate the resistor value necessary for the columns 8x8 led matrix?

I am building an 8x8 led matrix using 5mm LEDs (3.2V, 20mA). I connect it to the arduino UNO through the I2C using the GPIO expander MCP23017. The circuit is as follows: A matrix column is made up of ...
0
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1answer
39 views

HZX D882 transistor not blocking 12V DC current

I am not too savvy with electronics so I apologize in advance for any major ignorance on my part. I am trying to use a transistor (listed in the title) as a digital switch for my Raspberry Pi 4 to ...
0
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1answer
71 views

Calculate the time constant for a RC circuit

The switch S has been closed for a long time, and the it is opened. I want to calculate the time constant for the RC circuit below. I don't know how to tackle this problem, is the time constant for an ...
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0answers
39 views

How to calculate \$Z_1, Z_2\$ and \$Z_3\$ in two-port circuit?

I should calculate \$Z_1, Z_2\$ and \$Z_2\$, where \$a_{11} = 1.8, a_{12} = 2kΩ, a_{21} = 1*10^{-3}S\$ and \$a_{22} = 5/3\$? Also, all impedances are resistive, i.e. resistors. I have no idea how to ...
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0answers
25 views

Centering joystick potentiometers in a controller

I've replaced a joystick in my Dual Shock 4 controller, because it was getting stuck. The readings of the new joystick are offset to right and down. I've read that you can recenter the readings by ...
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2answers
57 views

Can someone help to find me a horizontal (90degree) connector? [closed]

I am having this connector - FH40-30S-0.5SV. This is a vertical connector and I am requiring a connector with similar pitch and pin count but instead of vertical (straight), I want horizontal (90 ...
0
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3answers
77 views

Purpose of resistor to ground in video-amp circuit

I was watching how to make a nintoaster, that is, an NES (Nintendo Entertainment System) in the form of a toaster. The video is here. One of the things he does in the video is building a video-amp ...
0
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2answers
102 views

How do I safely discharge a 3900 pF 3 kV (and 9 kV) capacitor?

I am planning to built a circuit with 3 polypropylene film 3900 pF 5% 3 kV DC radial capacitors connected in series. Before I start this, I want to make sure the capacitors are safely discharged. I am ...
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3answers
1k views

Why must the voltage drop over resistors in parallel be the same?

I am wondering why it is the case the when resistors are connected in parallel the voltage drop over them must be the same? The reason I have seen arguing for this is that the electrons before the ...
0
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1answer
92 views

All time up circuit

i'm new in this domain, but I like a lot. So, I have a question: I have a circuit with 20 LED (series + parallel 50mV, 3V), and I want to stay HIGH all time, except when I get a signal from another ...
0
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0answers
47 views

Motor controlled using Rpi 3 and 12V power supply

Could someone please assist me with the below circuit? I can't seem to get it to work. I am using a 12V power supply and Raspberry Pi 3. Apologies, I am very new to circuits. The DC motor does not ...

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