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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17 views

Diode 2 power supplies and voltage divider tasks

I have borrowed this analog - electronic book from 1991 at the library, and i am doing some tasks, i find that the book is not explaining , nor giving formulas to make me understand what i am really ...
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1answer
53 views

Stereo-Mono circuit after passive bandpass filter

If i put a passive RC band pass (high pass + low pass) filter before the amplifer and right next to it I sum the channels with 1-5 k ohm resistors, then the amplifier is turned on,is there a ...
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0answers
65 views

Resistor Madness… which way to read? [on hold]

I saw the result for 6-band resistors, but I'm trying to read 5-band. They seem to be evenly spaced and both directions give valid yet different values. The paint on these resistors is spotty in ...
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2answers
45 views

If adding resistors in parallel decreases total resistance, why doesn't the voltage in the circuit change?

I'm sure I'm missing something basic, but here we go: If adding resistors in parallel decreases total resistance, why doesn't the voltage in the circuit change? Does the current increase to match ...
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2answers
35 views

Mixing 2v and 3V LED's and calculating resistors

Are series groups in parallel better than strictly parallel with a resister on each leg? And for parallel do I calculate Ω just for each voltage LED or do I need to somehow do a calculation that takes ...
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2answers
62 views

Combining resistors in series with a voltage source in between

Am I allowed to combine the resistor R and coil Xl as if they were right next to each other? I want to make this into a current generator, without many transformations.
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2answers
27 views

How is the resistor value for boost conversion calculated?

I'm looking at MCP1640 and in Section 5.2, an equation for calculating RTOP is presented. However, the two examples underneath have RBOT = 309kOhm. How did that come about? Is 309kOhm some standard ...
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2answers
96 views

Noob trying to select resistor for 3 LEDs

So I'm making a parallel LED circuit using THREE CREE x-lamp LEDs which typically run at ~ 3.1v @ 350 mA, but they can max out at 1000 mA. I'm putting a resistor for each LED. So my logic may be ...
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53 views

Resistance to use with an LED to check if capacitor has been charged

I'm currently using this basic circuit to charge a capacitor I have: Now, I have three power sources which I use: 9V, 12V and 18V. I am using this capacitor to produce sparks to ignite hydrogen. ...
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4answers
535 views

Jumper or resistor?

I have in my BOM (Bill of materials) the following component CR21- 000-T and in the datasheet of the component : CR, CJ series is specified CR21 series as 0805 resistor. But the 000 is specified as ...
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0answers
72 views

About pull up or pull down resister [closed]

If a pull up or pull down resistor is connected between two ic then how to calculate the voltage drop across the resistor
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3answers
129 views

LED without resistor

I know Ohms Law, i know leds need resitors. My scenario is this: I need to make a little circuit that controls 2 RGB leds with a 9 Volt battery. This gives an avergare o 5 hours of light before the ...
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1answer
24 views

Choosing the correct thermistor

I need help choosing a thermistor. I’m not sure what I need to look for. Let’s say I have this circuit measuring temperature: I have a range of temperatures from 0 to 10 degrees that I need to ...
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1answer
88 views

Can I connect a MOSFET to an Arduino directly?

I have the following electromagnet and plan on connecting it to the following MOSFET which will be controlled by an Arduino (I'm thinking analogue or PWM). Do I need any other parts (resistors etc.) ...
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0answers
43 views

How to model the energy (heat) dissipating from a power resistor? [duplicate]

The issue I'm currently struggling with is: What is the mathematical relationship between power dissipation and temperature in a resistor? The project I'm working on is a controller card for a ...
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1answer
101 views

Theoretical infinite voltage here! Where's the problem?

Update: Thanks Spehro Pefhany for finding the issue! I've got a formula deduced which should - in theory - suggest that a battery with no external load connected should have an infinite external ...
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2answers
410 views

Do I Need a Series Resistor in Front of a Blinking LED?

I bought LEDs with a built-in chip which make them blink. The type of the LEDs are Kingbright L-56BSRD-B. The complete spec sheet is here. After reading the spec sheet I do not know if this LED needs ...
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1answer
44 views

What is a good resistance value for voltage divider to measure LiPo voltage with Arduino

(Full disclosure: I'm a newbie.) I'm trying to measure my 4S lipo's cell voltages using an Arduino Mega. I know that I should use a voltage divider (actually, several of them) and I think I ...
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1answer
54 views

LED Poster configuration

I am helping my sister make a LED poster for a concert she is going to. I am using a foam board with some letters she placed on there. I am then going to add LED's on top of the letters to spell them ...
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1answer
98 views

Choose the right resistor for your RGB led (calibrate the colors)

Calibrate RGB leds with the correct resistor Playing around with some microcontrollers and multiplexed leds i noticed that i always need to fix the colors of each led rgb output softwareside... thats ...
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3answers
65 views

Accounting for temperature changes in circuit design

In my last post about a simple circuit: +12V -- R1 -- LED1 -- LED2 -- LED3 -- ground A user said: ...you should account for temperature changes and variation between parts. Not all parts (even ...
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3answers
441 views

Resistor will heat up on what amount of current?

I tested a 470 ohms resistor with 35mA DC current flowing and my resistor is heating up. On my final design I have created a voltage divider circuit using ...
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1answer
43 views

Calculating resistor values for RPi circuit detecting AC current using H11AA1 and PNP transistor

I've got an electronic doorbell system (Aiphone IE-1AD) that sends a ~15Vac signal when the button is pushed. I used this blog post on detecting a signal on a similar door bell using a moteino ...
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1answer
58 views

Is it possible to reach 800 deg Celsius on copper? [closed]

Hi im totally tired of searching it. i want to heat a copper bar of 2*2*1 cmm to 800 deg celsius. i think it is possible by Kanthal,Nichrome wires. So please tell the required length, diameter and ...
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1answer
65 views

Most efficient way to drive a low power LED at half brightness

I'm working on a small project where efficiency is very important (every mA counts). I need to drive two red 3528 LED's in series and only have a 9V DC source. I want the LED's to be only around half ...
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2answers
81 views

What resistor should I buy (More than 2kW peak power)

Im using a resistor (68Ohm) to discharge a capacitor bank rated at around 400V. This is the graph of the current and the power in the resistor, as you can see there is a 2KW (4.5A) peak. But it's just ...
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2answers
37 views

Connecting AC analog amps meter

I'm a hobbyist/newby and I buy some items to build a cheap nichrome wire heater.First I buy a 50feet of 22gauges nichrome wire. For 120V AC source , I need 8feet of this nichrome wire to get desired ...
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1answer
50 views

How to drive luxeon Rebel LED

I was working on a project regarding building a high power LED driver as a excitation light to excite the florescence in the plant tissue. I want to turn the LED on and off at around 200Hz~10KHz.I ...
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2answers
66 views

Best configuration for 400W resistive heating device

Suppose I wanted to heat a large aluminum disk with joule heating. I would use one of its flat faces, which has a radius of about a foot (30cm, SA = 0.28 sq m) and enough resistors to dissipate 400W ...
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1answer
41 views

Installing a USB-A Port on D-Link DIR-300NRU B7 with Ralink RT5350F Chipset [closed]

I am writing to enquire about the installation of a USB-A port into the existing but soldered pins on DIR-300NRU B7. The board is given below: The USB pins are located on the bottom right. The ...
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2answers
90 views

Not understanding Forward Voltage and Voltage Drop

I have a simple circuit: +12V -- R1 -- LED1 -- LED2 -- LED3 -- ground Falstad simulation link If the Forward Voltage of an LED is 3V, and the Forward Current is 20mA, I can (I believe) calculate ...
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1answer
43 views

One shot pulse Push Button

How could I make a circuit where whenever a push button is pressed, the output would be a single pulse ? The pulses duration has to always be the same regardless of how long the button is held down. ...
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2answers
23 views

Cermet potentiometer temperature coefficients

I'm engineering a system that is temperature-sensitive, between ~-10-30C. I've moved to using cermet potentiometers because of their sub-200PPM/C temperature coefficients. If I wire such a pot with ...
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1answer
163 views

AVR switch best practice

After reading a lot of posts (here and on the web), I am a bit confused. All I want to do is to get the best practice of push button connection to AVR. I have 2 "sections" to my question. the first ...
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1answer
55 views

About finding equivalent resistance

The figure below is the schematic of the circuit, I have to admit that this is a homework question which I have stuck for a while. I try to use Wheatstone Bridge theory, but here in this question ...
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1answer
54 views

Negative resistance in Thevenin equivalent using elementary devices?

Is it possible to generate a negative resistance Thevenin equivalent using just resistances, ideal voltage sources, ideal current sources? I need a negative slope straight line I with respect to V. ...
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3answers
88 views

One resistor on two LEDs [duplicate]

This question is a little bit stupid and silly. As I am chemist, I don't remember electricity physics very good. As I remember it shouldn't harm anything, but I need to be sure. LEDs will be ...
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1answer
52 views

Check if bucket has water left

I want to build starter and simple auto self-watering system. I need the pump to take the water from a bucket, which means I need to check the water level on it and alert if too low. I want to do ...
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5answers
100 views

Parallel Resistor Calculation — Higher Equivalent Resistance

\$R_1\$ and \$R_2\$ are in parallel. What should be the value of \$R_2\$ if \$R_1 = 100\Omega\$ and their equivalent resistance is \$1\text{k}\Omega\$?
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2answers
89 views

0402 versus 0201 resistor footprints

I am writing a manufacturing specification for our contract manufacturing. So far, the smallest component on our PCB is a 0402 resistor, however, I would like to specify a process that will be ...
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1answer
39 views

Calculate absolute values for resistor bridge to use with op amp lm358

I'm trying to make a simple thermostat using a thermistor and an Op Amp. The relevant part of my circuit diagram is shown below. simulate this circuit – Schematic created using CircuitLab ...
2
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1answer
28 views

semiconductor resistor vs resistor in SPICE modeling Altium

I'm doing some SPICE modeling using altium and would like to apply the temperature coefficients of the passive components for a more accurate simulation. However, as far as I know, in altium the ...
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1answer
49 views

How a P-Channel Mosfet works with a pull-up resistor

I have been desperately trying for days to troubleshoot this h-bridge I build so I'm trying to completely understand it first. What I don't understand is how R1 and ...
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2answers
350 views

Quick question about aux cable DIY

I've been planning to make an aux cable for my BMW 3-series, because the original costs 80€... So I've read a couple of DIY and I've found this So I've ordered the cable, capacitors, and the ...
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1answer
38 views

MIKROE-55 - LCD Datasheet [duplicate]

I'm a bit confused by the datasheet of a LCD (MIKROE-55). It says supply voltage is 3.5V (TYP), which results in as Supply current of 16mA. At first I understood this as: "connect K to GND and A to ...
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0answers
43 views

Single Transistor DC TO AC Circut

I have a question that may be rather difficult to ask and format however I will try. Now I am very new to electronics in general but in my spare time I play around with them a little bit. I have ...
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3answers
289 views

How many ohms do you need before you need a resistor?

Okay, I'm rather a bit confused here now. I am trying my first real circuits, for some LED lighting. I tried making a little circuit last night, matching two LEDs in parallel on 4.5v of battery. ...
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3answers
125 views

Unusual resistor symbol: resitor with Z overlaid

I found this symbol in a vendor circuit diagram. What does it mean? It looks like they are trying to convey some sort of limiting. It's a resistor symbol with a line over the top that has both the ...
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3answers
496 views

what is the meaning of NOP in the schematic diagram?

what is the meaning of NOP in the schematic diagam?
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0answers
40 views

algebraic addition and subtraction within RC and RL

Why isn't it possible to algebraic add the potential drop of R and L within a serial circuit using alternate current? And why is ...