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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Miniature heater with more-or-less constant temperature. Need tip on element

I'm a software engineer with very basic knowledge of electronics. I have a project in which I want to make a small (cylinder of length about 100-150mm and diameter 20-30mm), localized heater that ...
2
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2answers
143 views

Learning transistor based circuits

simulate this circuit – Schematic created using CircuitLab In one of our electronic circuit tests, this question was asked: What is the output voltage of given circuit? This circuit ...
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26 views

thevenin equivalent using matrix method

Is it possible to determine the Thevenin equivalent of a linear network(of very high complexity) by using some matrix method?
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2answers
74 views

resistor's resistance value in any circuit [closed]

how can I find resistor value in any circuit ? please don't tell me anyone about colour code only tell How do I know that there used to resistor this.
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1answer
122 views

Does biasing of address pins require a resistor?

I'm a total newbie fooling around with a project of mine. I want to use a MCP23071 I2C port extender (Data sheet) for my arduino project. The chip has three hardware pins that must be externally ...
26
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4answers
5k views

Why do resistors still use color coding?

I always wondered why color coding is still used on resistors in 2014. Here is Wikipedia's word on the original reason why : Colorbands were commonly used (especially on resistors) because they ...
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0answers
48 views

E-series Enigma

I just found something that baffles me to no end. I programmatically calculated what should be the actual values for each number in the E-series from E6 to E48, and some of them do not match up with ...
2
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4answers
257 views

LEDs are burning. Cannot figure out why

I have a lamp that has LED driver producing 35 V (actually lamp driver says 16 - 28 V, but I've measured 35 V). On the lamp I have 7 LEDs (originally 5 + 2 I've added) with heatsinks that have burned ...
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1answer
43 views

Help compare my results to the maximum power transfer theorem and explain using algorithms

So below is an image of the relationship between efficiency of a circuit and the resistance of the load, as you can see the maximum efficiency occurs when the two resistances are equal. here is a ...
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5answers
694 views

Large Resistors?

Can there exist a resistor that can deal with current reaching up to 1000A or 10x time that value, and beyond? What about heat dissipation when massive amounts of current is required?
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1answer
51 views

Calculationg base-resistor between microcontroller and transistor

I'm curious, when connecting my 2N2222 transistor's base to a PWM output pin on my Arduino, I know the Arduino can deliver a maximum of 40mA current. The 2N2222 only requires around 5 to 10 mA on it's ...
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2answers
86 views

Slowing Down Capacitor Circuit discharge rate

I am currently trying to use a 5 Pin relay on a Motorcycle indicator circuit. The concept is I have a Daytime Running Light (DRL) that is in the same housing as the indicator. When the indicator is ...
2
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3answers
127 views

Identifying this resistor/capacitor

I'm having trouble to identify this (presumably broken) part for replacement: It was used in a broken LED power supply, with 220-240 V AC on the input and 120-200V DC on the output. I suspect this ...
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1answer
49 views

Motorised blind controller schematic - do I need to protect ICs with resistors?

I am making a simple motorised blind controller, which I want to have a "safety cut out" when it gets to its fully closed/fully open state. (So the user doesn't strain the motor keeping their finger ...
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1answer
85 views

Russian variable resistor datasheet

Can you please help me find datasheet for this 2.2 ohm variable resistor. I want to know if it can tolerate 20 amps. If you recognize the logo that would help a lot.
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0answers
88 views

Designing circuit with Arduino and optocoupler: beginners problem

Firstly, I am a beginning hobbyist starting doing some electronics and this is my absolutely first attempt in trying to automate something. Here is my circuit (or what I intend): I don't know if my ...
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2answers
64 views

Why increase in resistance of register used in circuit show lesser average power dissipation

I am working on 6 transistor full adder circuit. Red marked resistors (25k) are used to show all pattern of full adder correctly. But it show wired behavior. When I increase resistance from 25k to ...
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2answers
110 views

Resistor required for capacitor?

I'm currently working on some simple circuits to learn about circuitry, and being a Physics major I have a pretty good grasp of the mathematics and concepts, but I'm a little confused about ...
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2answers
100 views

Understanding resistors on inputs/outputs of op amps

I was looking at the schematic for Dave Jones' uCurrent, and I can't seem to make sense of why there are 270 ohm resistors on the inputs and outputs of the op amps in his circuit. The resistance is ...
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5answers
117 views

Which resistor to use for this LED

I'm looking to buy resistors for a Raspberry Pi project, but am getting conflicting information on which resistance to use for my LEDs. I will have three LEDs. The voltage from the RPi GPIO pins is ...
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3answers
89 views

Low power serial bluetooth module with Arduino

I plan to use the HC-06 serial bluetooth module with an Arduino Leonardo. To my knowledge, the Arduino's serial pins output at 5V with 40mA of current. The HC-06's datasheet says it will accept input ...
3
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3answers
204 views

Why resistor values are non-linear? What makes sense in 470 ohm? [duplicate]

I never figured that out. Why do we have 220 ohm and 470 ohm, rather than 100 ohm, 200 ohm, 300 ohm? Any particular reason? maybe it's just legacy from old manufacturing process.
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1answer
64 views

Calculate delay in long line

Assume we are connecting a lamp to a source but line (wire) is so long (for example 20Km): Will the lamp bright after connecting the source immediately? how much time it will be? Can we calculate ...
3
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1answer
243 views

Not sure if my calculation is correct, can anyone check this RC circuit for me?

Hello everyone, so in my book I decided to do this practice question but failed to notice that the answer was not given in the back of the book. If anyone can help me confirm my answer I would much ...
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3answers
181 views

Accuracy in translating voltages to currents for shunt resistors

I apply a constant 4ma current I to a resistor R and I measure a voltage V across. so the resistor \$ R = \dfrac{V}{I}\$. But when I apply \$ I_2=20ma\$ to the same resistor R and I obtain the ...
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3answers
234 views

Meaning of temperature coefficient for resistors

Is temperature coefficient of a resistor about the temperature of the resistor or ambient temperature or are they the same thing? What I mean to ask is that: Lets say I have a resistor and I have no ...
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1answer
641 views

What are the advantages of a shunt resistor vs. a hall effect sensor?

I'm constructing a boost converter, and I need to measure both the input current and the output current. Currents range anywhere from 25A to 200A, depending on the model. My controller is referenced ...
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2answers
49 views

Resistor Magnitudes in Voltage Dividers

I recently made a voltage divider that uses a 10 ohm (top) and ~90 ohm (bottom) to divide a source voltage of 5v to 4.5v. The resistor values I used was somewhat arbitrary, in that I just picked a ...
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3answers
191 views

Measuring Voltage across a resistor

I am taking my first steps into learning about electronics as a hobbyist and I am struggling to understand something about resistance. I have read about Ohm's law and it seems fairly straightforward ...
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2answers
72 views

Resistors in series current question

According to Wikipedia, the current of resistors in series will be Vin/R1+R2. Now I could be over thinking this but is that the current that you'll get out or is that just used for determining the ...
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1answer
134 views

Resistor in series and capacitor in parallel to ground

Could somebody tell me why someone would need circuit like that in supply rails? I assume it is for making DC voltage smoother by parallel capacitor. However, my 24V power supply has 500mA output ...
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5answers
2k views

Why are there so many resistors in a typical schematic?

I know that some resistors cause pull-up or pull-down or work as a voltage divider and/or current divider. But sometimes I cannot understand their function in some simple circuits: Take this motor ...
3
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2answers
288 views

Grounding unused leg of bussed resistor?

I've got a bussed resistor: The package I'm using has 13 inputs and 1 output, tied to ground. I'm only using 11 of the inputs. Do I need to worry about the floating end of the two unused inputs? ...
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3answers
127 views

A series resistor behind a reverse biased zener diode

simulate this circuit – Schematic created using CircuitLab If the Zener is rated at 4V, and the resistors R1 R2 are both 300ohm, may I know what is the value for Vout? I know this is a ...
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3answers
225 views

3 Watt LEDs in Series - Using constant voltage Source

I have searched everywhere for an answer to this question but I think its probably so simple that no one has felt the need to answer it. Basically I have 20 x 3 Watt LEDs and have a 80W Constant ...
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0answers
49 views

Can you calculate parasitic elements caused by using many breadboards?

Recently, I've had the idea of building a 4-bit CPU out of RTL (Resistor Transistor Logic). Because there are so many connections, I would prefer to build this project on many breadboards. I realized ...
0
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1answer
67 views

CX-20 Quadcopter Part

One of the ESC's on my quadcopter is missing a component. I am unsure what this component does or where to find a new part. Is it a sort of resistor?? What size? it features no markings that I can ...
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2answers
51 views

What potentiometer should I use for my led strip?

I have a led strip, this led strip is consuming about 2.5A @ 12V. Before, I was using an Arduino to modulate the intensity of the light with PWM but I realized that a simple circuit would be even ...
0
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2answers
109 views

Night activated LEDs

I want to use a photo resistor to make a circuit like this But instead of light causing the led to turn on, I want darkness to cause the led to turn on.
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1answer
74 views

Creating Heat with Resistors

I am trying to create a cheap and small heating element capable of reaching temperatures of at least 260 degrees C. I am considering using a resistor. Is there such thing as a cheap resistor capable ...
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2answers
131 views

Controlling a Stepper-Motor with 2 H-bridges

I think that I may have come up with a possible way to control a bipolar stepper motor using 2 simple H-bridges. The idea is to control the direction and the steps of the motor by switching the ...
0
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6answers
290 views

Why are resistor values constant in the face of changing voltage and current?

Small question, I see that resistors are labeled in certain increments (e.g 5, 10 50 Ohms), although a resistor outside of a circuit is completely without voltage and therefore current. Does this just ...
0
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3answers
104 views

Why doesn't linear resistance scale proportionally with the square of length?

I have an in depth question about basic proportionality of resistance. Why doesn't it scale with the square of length? I ask this because what is causing the potential difference on two leads is ...
7
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5answers
824 views

Question about resistors and LEDs

How can I find the right resistor to make 50% brightness in an led? I know how to find the right resistor to get the brightest but I'm wanting to find the perfect middle.
3
votes
3answers
367 views

Voltage rating vs. power rating of a resistor

My question may sound very basic, but I am very confused by the difference between the voltage and power ratings of a resistor. Vishay's document says: Rated Power The maximum amount of ...
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votes
3answers
151 views

When should you use a transformer instead of a resistor? [closed]

I feel like this was something that was never taught by my instructor in physics. Is there a certain rule determine when a resistor should be used over a transformer, when stepping down voltage?
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votes
2answers
90 views

Buzzer on Arduino UNO [closed]

I'm trying to connect a buzzer to my Arduino Uno to play a tone. Instead of giving a melody I will give a HIGH value which translates in to 5V. Since I don't want ...
0
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0answers
65 views

Do I need a resistor for powering a 3-12v dc motor with USB 2.0

I'm trying to make a project from instructables: http://www.instructables.com/id/ATtiny8545-POV-Display/?ALLSTEPS And the guy uses resistors for his usb cable and now I'm not sure if I need to use ...
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3answers
86 views

Batteries in parallel

What will happen if 2 or more ideal batteries with different emfs are connected in parallel across a resistor? Just curious to know what folk around here think..
2
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3answers
87 views

5 Band resistors and correct orientation

few days ago i bought few (about 500) resistors and i noticed that they have 5 color bands instead of 4. My question is how do i count them (which color is the tollerence) and how should i put them? ...