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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2
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2answers
220 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? ...
-1
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3answers
78 views

Having a series resistor behind [on hold]

We know that a Zener diode regulates voltage to its written rating. Looking at the drawing below, if the Zener is rated at 4V, and the resistor is 300ohm, may I know what is the value for Vout? ...
1
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3answers
108 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
46 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
36 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 ...
0
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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 ...
0
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2answers
104 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.
0
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1answer
68 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
90 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
262 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
102 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
804 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
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3answers
329 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 ...
-2
votes
3answers
131 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
72 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
45 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 ...
-2
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3answers
80 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
75 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? ...
1
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2answers
174 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 ...
0
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0answers
72 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
65 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 ...
1
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2answers
83 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
115 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
73 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 ...
0
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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 ...
0
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2answers
62 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 ...
0
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1answer
57 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}\$ ...
0
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2answers
129 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
64 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
votes
3answers
138 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 ...
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3answers
48 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
48 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
votes
1answer
129 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. ...
1
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3answers
128 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 ...
0
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0answers
61 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
84 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?
1
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6answers
312 views

Current doesn't equal what I expected

I'm making a simple LED circuit. I have a 6V power source, and a LED with 2 forward voltage and that requires 18mA. I calculated the resistance by dividing the voltage with the required amps (6-2 / ...
5
votes
4answers
773 views

When to use pull-down vs. pull-up resistors

After learning and experimenting with microcontrollers, the concept of pull-up- and pull-down resistors has been understood and saved to my hard drive. I now understand when and how to use them, and ...
2
votes
2answers
104 views

How do I use an adjustable LDO regulator to power devices with USB that usually use AA/AAA batteries (or should I)?

I want to use USB to power devices designed to work with one, two, or three AA/AAA batteries. Three seems to be the trickiest, because it involves dropping the voltage only ~0.5 V from 5±0.25 V to 4.5 ...
3
votes
2answers
156 views

How do I calculate what resistors I need for RGB LEDs with 3.7V? [duplicate]

I have a total of 4 x RGB LEDs. I am hoping to power these as well as a RFduino BLE module with a 3.7V lithium rechargeable battery. I was just wondering how I would go about calculating the ...
4
votes
3answers
587 views

What is the voltage across the circuit shown?

I'm having trouble finding the voltage between the points 0 and 1. Can anyone help me? By applying KVL on each closed loop I find that Vi+IiRi is constant for every "i" but I don't know how to find ...
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votes
1answer
58 views

Why do electrons in battery not “go out” if there is no resistor in circuit? [closed]

This is what I always thought: Why do we always need resistors in our circuits? What if we use one battery and just a piece of cable without a resistor? Why do electrons in a battery not "go out" in ...
0
votes
1answer
147 views

How to arrange resistors for certain resistance

This question is like this one. I have two 1 ohm resistors, six 2 ohm resistors, and want 2 ohms total. All resistors must be powered (since they are actually speakers.) How do I do this? Ideally, a ...
1
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2answers
122 views

What is the significance of 75mV in available 100A current shunt resistors?

I'm considering doing part of How to Install an Ammeter in the Black & Decker CMM1200 Cordless Electric Mower but first with just a shunt resistor and voltmeter, versus hooking in a dial ammeter ...
1
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2answers
52 views

Shape specifications axial lead resistor

We are looking for specifications of the shape of an axial lead resistor. In other words what is the radius in the middle of a resistor and at the ends,...
1
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0answers
33 views

Total DC resistance of thin-film resistor with truncated contact pads

I would like to calculate the DC resistance across a rectangular patch of resistive material with contact pads that are less than the resistor width. The resistive material is a thin film with a ...
2
votes
3answers
215 views

How to deal with a complex circuit of resistors and capacitors?

simulate this circuit – Schematic created using CircuitLab Assuming i have the circuit from above and i need to find the current through every resistor and capacitor. the switch opens at ...
2
votes
2answers
197 views

Finding equivalent resistance for time constant in R-C circuit

Given the first order circuit above. The switch has been closed for a long time and is opened at \$t=0\$. Find the equation for the voltage \$vc(t)\$ across the capacitor after the switch has been ...