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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44 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
141 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
57 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
230 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
170 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
211 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
432 views
+100

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
43 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 ...
3
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3answers
183 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
67 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
127 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
106 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
150 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 ...
0
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0answers
47 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
44 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
42 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 ...
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2answers
106 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
72 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
101 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
272 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 ...
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3answers
103 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 ...
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5answers
806 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.
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3answers
341 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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3answers
138 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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2answers
79 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 ...
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0answers
50 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
84 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..
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3answers
77 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? ...
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2answers
175 views

Transistor Ohms

I've built the circuit in the schematic below to control my TV, the D1 and D2 LEDs are the two mini LEDs from this IR Extender: I've cut it below the female headphone jack and I'm using my ...
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0answers
73 views

Equivalent circuit of resistor capacitor

I came across a capacitor that has a marking like this: 0.1uF+2x2000pF XY + 2MOhm 220V~ HPF fo 1.6MHz 7.75 560.7 it looks like this one below the only ...
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0answers
67 views

Maximum Ohms for IR LED and transistor

I bought a cheap IR extender and I'm trying to use the small sticky cases to control my TV using a Raspberry Pi. The extender has two "heads" with a small IR LED in it and they were connected to the ...
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2answers
85 views

Please explain the purpose of the resistors in this scenario

I came across this schematic and I am wondering why there are two different resistors on the output pins. I know that there has to be some resistor because otherwise if one pin was hight and the other ...
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4answers
122 views

Replacement for no longer found sand block resistor in subwoofer amp?

My SVS PB13-Ultra subwoofer stopped working. It happened after a voltage sag, probably followed by some spike. After inspection, the fuse and a power resistor were blown. I am sending you pictures ...
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2answers
75 views

Messing with rgb leds and have a question

I have some LEDs that I'm wanting to use in a project. I would like to know what's the best resistor I would need to get the most light out of the 3 different colors using a 12v source. I've measured ...
0
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1answer
32 views

Current of a circuit with regulator

When the specification of a regulator says that output is 1A for example the whole current of the circuit will be 1A? For example I have a regulator in series with a 100Ω resistor and a 7V source.The ...
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3answers
88 views

How to determine wattages on an applications note schematic?

Specifically, I refer to Fig 18 on Page 14 of this datasheet for dual supplies. Really nice, really "simple" to use 2x40W power amp I want to try out. Unfortunately, I'm a newbie and their schematic ...
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2answers
70 views

STM32F3 Discovery 5V output

I want to use a STM32F3 GPIO (3.6V) to drive another device using 5V input. Which is the correct way to do so? I know that is possible to use the open drain mode on the GPIO, but I'm not sure if I ...
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1answer
59 views

Do I have to use a sense resistor? MC34063 Step-Up

Do I need to use a sense resistor for the MC34063 Step-Up Circuit? I would like to step-up my voltage from 5V to 40V. After doing the math, I've found that I will probably need a 0.16 Ohm Sense ...
1
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1answer
53 views

Resistors in parallel?

From what I understand, the proof is suggesting that $$i(t) = (\frac{1}{R_1}+\frac{1}{R_2})v(t)$$ implies that replacing the two resistors with 1 resistor of value \$\frac{1}{R_1}+\frac{1}{R_2}\$ ...
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2answers
131 views

L7805CV won't go higher than 7.5

I am trying to use a STMicroelectronics L7805CV to increase voltage from 7.5v to about 12v, but I can't get it work. I've placed 470 ohm resistors between out and common and between common and ground, ...
0
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1answer
65 views

Connect two-function brake light to three-function car circuit

I need to replace my 12VDC (bulb based) brake lights but I am unable to find a three-function light (Running/Brake/Off) with the same specs. I did however find a two-function light LED fixture ...
2
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3answers
145 views

What kind of metal are the legs of resistors made from?

Can anyone tell me what kind of metal is used in electronics to make wires going in/out to the elements? Can longer of this metal wire be found anywhere? Actually I am looking for sth like copper wire ...
1
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3answers
52 views

Do I need pull-down resistor on Enable pin cd74hc4051

Can I directly connect enable pin to ground? I am not going to use it. datasheet Also can I connect all unused pins of LM324 op-amp to ground through single resistor or what configuration does it ...
0
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1answer
50 views

I used led calculator and it gave me a different solutions, in one of the solutions says “ the array draws current of 100 mA from the source”

With another solutions mA just goes up, 125 mA, then 175 mA, 250 mA,I want to know which solution is best,the one that draws less mA will be best?
2
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1answer
140 views

Resistor symbol with a dot

I was looking for some reference and i found this resistor symbol: All the resistors in the schematic (several sheets) have the same symbol, so i concluded that it means nothing, but i'm not sure. ...
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3answers
134 views

Best way to drop 12V fan to 7-9V? [closed]

So my Xbox one PSU died and microsoft doesn't sell official ones yet, so I bought a third party one and the fan that is in it is a 12V blower fan with 2 wires running right to the board (it says 12V ...
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0answers
69 views

DC Voltage of a 12V AC transformer after rectification

I want to drive relays using Method 2 of the following question: What is the most economical way to drive an array of single coil latching relays? This basically means that any time the relay is ...
0
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1answer
85 views

What kind of temperature sensor is this?

What kind of temperature sensor is this? What would be the best method for getting a reading from it?