# Tagged Questions

A resistor obeys Ohm's law (V=IR); the current through it is equal to the voltage across it divided by the resistance (equivalently $I=\frac{V}{R}$)

509 views

### Capacitor in parallel with resistor on xoscope amplifier schematic

Short version: Why is C3 necessary in this circuit? Explanation: The schematic for the input buffer/amplifier circuit for xoscope is made up of subsections that are mostly broken down in the ...
818 views

### If I'm going to use a potentiometer as an adjustable voltage divider, does the tolerance or resistance matter?

Here's what I working with. I'm researching some three terminal potentiometers for use as adjustable voltage dividers. The outer terminals are connected to 0V and 5V respectably, so as I turn the ...
1k views

### How do I calculate the resistor value for this circuit

I am playing with a power supply that went bad, to expand my knowledge and just see if I can repair the circuit level board. Here is my problem. I have a resistor that burned up. I have no idea of ...
356 views

### Simple voltage divider question

So two resistors in series can be a voltage divider. So say I have the following circuit - From what I have read the voltage gets split across the resistors based on their resistance. So there will ...
1k views

### 1.8V to 5V, still not comfortable with transistors

I have a H-bridge IC L293DNE that needs 5V input signals to operate, however my available outputs are only 1.8V from a Gumstix Overo GPIO pin. I have a power supply that supplies me with +5V 1A. I've ...
618 views

### Resistor Noise - What it will have effect on, in a circuit?

Reading the article resistor noise and knowing that resistor noise is in the form of Voltage (is that thr right expression?!) leaves me wondering that this generated voltage will have only eefect ...
717 views

### Very basic questions on resistor and gnd

Im a total beginner. I bought an arduino starter kit and this is the first sample program - it makes an LED blink. The accompanying text gives no theory about what is happening in the sample programs ...
319 views

### Reducing number of resistors

I have question about reducing number of resistors ... Well, it will be better if I show you the schematics. This is my first scheme: That's what I have. The thing is, I know what only one LED will ...
929 views

### Transistors: why are resistors needed?

I have a solid state relay which needs at least 3V to activate, and I need to toggle with a 2.3V output from a microcontroller. I've also got a 6V 1A power supply which I can use to power the relay. ...
179 views

### How to properly store components efficiently and effectively [duplicate]

Possible Duplicate: What's the best way to store and categorise resistors/capacitors/ICs/etc? I have MANY resistors and many other components as well and currently I am using a very ...
1k views

### EMF Detector Sensitivity

A fun little project I've been working on is an EMF detector using my recently acquired Arduino. It is based off of the guide at http://www.aaronalai.com/emf-detector, primary differences being my own ...
652 views

I have a 7.5V, 2A, Radio Shack AC adapter and I need it to be a 7.5V, 1.5A power supply. It has one of those tip-ring style plugs on the DC end that plugs into a device to provide power. I need the ...
777 views

### Not sure how to name what this resistor is doing?

I have a basic circuit that uses a photoresistor powered by a five volt source. I had made this project to show my son about various sensors and had used a circuit I had found online. It looks ...
280 views

### How is the fact that the resistor used to limit the LED current dissipates some of energy addressed in lighting applications?

LEDs can't be connected directly to a source of power - only in series with a current limiting resistor. Which means that when the LED is powered some power is dissipated by that LED and some power is ...
389 views

### mute de-amplify sound volume

I want to de-amplify the sound volume of my television. My native language is not english, and I do not know the correct word, if any, for the opposite of amplify. When my TV is turned from volume ...
1k views

### What's the automatic equivalent of a variable resistor?

I have a circuit which controls the volume on a speaker by a wheel which is attached to a variable resistor - I want to reproduce this but instead of using a manually operated variable resistor, I ...
272 views

### resistor equivalent for non parallel non serial

What formulas do I need to calculate the resistor equivalent for not just the normal parallel and serial connection? e.g resistance from A to B og these five resistors: Is Kirchhoff's laws and hard ...
9k views

### How do I calculate the required value for a pull-up resistor?

There are many tutorials that use a pull-up or pull-down resistor in conjunction with a switch to avoid a floating ground, e.g. http://www.arduino.cc/en/Tutorial/button Many of these projects ...
1k views

### Voltage Required to Ignite 10ohm resistor

I just read http://www.bigclive.com/ignite.htm It shows igniting a 10ohm resistor with 12 volts. I was wondering, could a 10ohm resistor be ignited with less voltage(say, 9Volts), and if so, what is ...
2k views

### Why do you need 2 resistors when hooking up a transistor as a switch

What is the point of R2 in the following diagram: I get that R1 controls the current to the Base, but what does R2 do?
256 views

### Dual voltage LED circuit

I am designing a board that will eventually be connected to a front panel with LEDs. In the meantime, I have a set of LEDs mounted on the board itself for debugging and whatnot. To debug this board I ...
280 views

### Voltage dividers and resistors

I just encountered the voltage divider a few days back. It was working, yes. But i'm confused that in my circuit, I needed to output 1/2 voltage so I used equal values for the two resistors. And from ...
174 views

### Reading a simple diagram, how to practically implement this on a breadboard

So yes, I'm brand new to circuitry, and I'm looking to implement a very simple diagram in order to boost a 3.3v output to 12v output. I've picked up a lm317T from the local electronics shop and I'm ...
479 views

### When looking for resistors, what is the W for?

I'm looking for a variety of resistors for my project. Since I'm so new to this, I don't have the slightest idea what I'm looking at. Essentially, as I research ideas, I get recommendations that ...
616 views

### Which Value of R1 do I use for thermistor-controlled fan?

The MOSFET I am using is IRLU014PBF-ND. I am using a 10k thermistor, and a 24VDC fan, instead of 12vdc.
149 views

### Graphical solution?

I have the following circuit. where $R_{G2} = 4.7\mbox{ }k\Omega$ I need to find the operating point that produces maximum gain. Then I have to find $V_G$ graphically. At the end I have to ...
750 views

### Battery circuit power drain

Bit of a newbie question here... I want to build a battery powered LED light for use outdoors. So basically needs to be pretty bright and last a while. If I have battery rated like this: ...
567 views

### Single resistor powering multiple LEDs in parallel where current through resistor is lower than max allowed current for an individual LED

While writing an answer about using multiple diodes connected to a single resistor, I stumbled upon a case about which I haven't read a lot: What happens when we set the resistor so that it sets the ...
10k views

### Why exactly can't a single resistor be used for many parallel LEDs?

Why can't you use a single resistor for a number of LEDs in parallel instead of one each?
2k views

### Resistor suggestions for colorblind person

I'm a developer who has always had a love of the low-level electronis, but I have always been intimidated by it since resistors all seem to be color based and as a color-blind person, this is ...
7k views

### How to reduce voltage without using Transformer?

Is there any way to reduce voltage without using transformer? I have a supply of 24 volts AC @ 1500mA (1.5A) and I want to convert it into 6 volts @ 500mA. Because I have to supply the 6 volts to the ...
252 views

### Is memristance missing from our models?

Since memristors are fundamental two-terminal, passive elements, is memristance a missing contributor that should now be included in distributed element calculations and parasitic extraction?
527 views

### Why shunt resistance has 3 line?

I know that the there is two lines to connect it to the integrator like the below picture , so what the 3rd line do ?? how to use it ?? is it necessary ?
389 views

I've been building a light based alarm system, using an LDR, Op Amp, AND gate, some resistors, and an output of buzzers.. Here's my circuit so far... It beeps when it senses light as well as being ...
425 views

### How to use resistors?

I have a power supply of 5 volts @ 1A. I want to reduce the current from 1A to 250mA. Which resistor should be use? I tried this equation(Ohm's Law): R = V / I = 5/(0.75) = 6.66 Ohms. I tried ...
1k views

### Determine suitable resistor for the base of transistor as switch (NPN)

I have designed a program to count the frequency and time period of the pulse generated by a 555 timer IC using PC Parallel port. I’ve connected a base of BC547 (NPN) transistor to the output pin (no. ...
471 views

### Hand Warmer Heater circuit . Need tips for element

So I have this simple project I'm working on to make a rechargeable hand warmer, but I can't figure out what type of resistor I should be using for the element. Does anyone have any ideas? I'm trying ...
2k views

### Differences between parallel resistor-capacitor filters and series resistor-capacitor filters

I've only worked with series resistor-capacitor filters before, so I'm not very clear about the operation of parallel resistor-capacitors filters. Can somebody explain to me what are the differences ...
509 views

### How current limiting resistor for LED affects current and voltage drops?

I'm having a bit of trouble understanding currrent limiting resistors in simple LED circuits. I know that I can determine the optimal resistor like so: $\displaystyle R=\frac{V_{s}-V_{f}}{I_{f}}$ ...
382 views

### Not use current limiting resistor for switching device on off using TIP122 possible?

I wanting to control MP3 player and amplifier box through PIC board. My project is doing announcement when person standing in near PIC board with proximity sensor. When proximity sensor detecting ...
263 views

### Would any current flow when batteries and resistors are set up like this?

What would the current flow be through the 1 ohm resistor? They are constant voltage sources, not batteries.
314 views

### LED “Underdrive”

Is there any possible way I could've messed up this LED? I just found a bi-colored flashing LED this morning and I hooked up different voltages on it in the following order: 3.7V 3.8V 4.5V ...
152 views

### Voltage problem in printed circuit with switches

I've got a simple circuit consisting of a 74157 MUX, whose entries come from switches. These entries have also 10k pull-up resistors, so when the switches are open (default), inputs are at 5V. When ...
506 views

### Resistor wattage?

I'm new to electronics, what types of resistors should I get to make this circuit? I have 6 IR LEDs (High output infrared LED 5mm 1.2VDC 100mA 940nm) that will be connected to an Ardunio Uno. Going ...
608 views

### What is the job of the capacitor in a 555 circuit?

Let's say you've got a standard astable multivibrator (AMV) 555 circuit that includes all the wiring, two resistors (R1, R2) and a capacitor (C1). I wonder what is the purpose of the capacitor and how ...
496 views

### Working with the MSGEQ7 clock input

I just got a MSGEQ7 equalizer chip. I have everything wired up like http://nuewire.com/info-archive/msgeq7-by-j-skoba/ except for the 33pF cap. I have no idea where to even find those. I think somehow ...
1k views

### 120v variable resistor controlled by 5v?

I want to do some work with automating christmas lights later this year and my friend and I think relays may be the way to go. After a little more thought, I think it would be cooler if the lights ...
198 views

### Am I drawing more current if I'm giving multiple paths from supply to ground?

Illustrated as such: Am I drawing more current in the first case than the second case? Would this drain the 9V battery faster? Thanks
1k views

### Replace tiny resistor with a physically larger one?

I'm looking to replace a resistor on a key sender unit from my Mum's car. The part is about 2 mm and too small for me to solder. Can I replace it with one that I can work with easier as it is bigger? ...
3k views

### Whats inside a resistor?

How does a resistor "resist" current/potential? I know it's an elementary question, but I'm sure others are wondering too.