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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ESP8266 using LOW-Level with GPIO0

as you know to put ESP8266 into bootmode GPIO0 should be connected to the ground. That works perfectly, but the problem I don't ...
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1answer
62 views

What is the purpose of resistance & capacitance in parallel to Load ( refer ckt )

What is the purpose of resistance & capacitance in parallel to Load ( refer ckt ) ? As per my understanding these capacitor & resistor is for filtration purpose ( kindly clarify the same) . ...
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1answer
64 views

Does it matter if i put a resistor in backwards? [on hold]

Simple, curious, yes/no question: Can you put a resistor in backwards?
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62 views

Can some help me understand this ground switching circuit?

I am trying to understand a switch circuit related to a project that I am working on. Pin 1 - 12v signal for switch backlights Pin 2 - 12v signal for switch on/off indicators Pin 3/4 - Unused Pin ...
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1answer
61 views

Problem with high-pass filter - signal gets shifted down

I have a problem where I am passing pulses received from a photo-diode into a high pass RC filter. Circuit shown below. The pulses are being received at 25Khz. Before the filter, the pulses are ...
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5answers
120 views

Rules for choosing power rating of a resistor

Let's say we're designing a system, and within it we have some resistor \$R\$ with a voltage difference \$V\$ across its terminals. Then it dissipates power \$P = V^2 / R \$. Of course the resistor ...
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1answer
27 views

Need help understanding the concept of “Circuit model of a discharging RL circuit”

I don't understand the statements for t<0 and t>0. Why does this happen?
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0answers
34 views

Series Gate Resistor needed at low Capacitance?

even though this question has been answered before for various scenarios, I would like to ask for a generic advice. So I want to drive a certain resistive load from a microcontroller pin. Let MCU be ...
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1answer
63 views

What resisters for inverting op-amp should I use?

I am not an electrical engineer by any means so go easy on me here. I am simply experimenting with a speaker amplifier. My situation: I have a Clarion xc1410 4-channel amplifier with a 10k input ...
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2answers
113 views

Resistor failed open

I am using this voltage divider circuit on a control board. Customer brought a board back stating the board wouldn't function after a few months in the field. After inspection, I found the 4.3kΩ ...
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2answers
41 views

Measure current in power suppy [on hold]

I have a power supply which I ordered online for 100 amps. I thought it will be digital but its an old fashioned type. I want to build the current sensing circuit to find out how much current is ...
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1answer
39 views

How to sum resistors in parallel and series?

I know how to add resistors in parallel and resistors in series, but i don't understand how to differentiate between resistors in the format shown: simulate this circuit – Schematic ...
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0answers
32 views

Increase Motor Speed By low Voltage (AC) [on hold]

i want ask question How i can increase motor speed AC not DC ? IF i set arm from this arrange motor , gar , arm . this arm will increase this speed . if yes what is relations with it and speed ...
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1answer
50 views

Voltage Conversion Module

So firstly i'd like to say I'm relatively new with electrical engineering, nothing more than backyard experience. However I am a computer programmer so I can grasp the concepts fairly well. One of ...
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1answer
38 views

the proper way to wire up multiple supply rails

I am making a hexcopter for a shool project that is going to be powered and controlled via an arduino project. my current setup is as follows: Where the linear regulators are the 6 speed controllers' ...
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1answer
23 views

Not gate dividing voltage

simulate this circuit – Schematic created using CircuitLab I am working on a binary calculator using 2n3904 NPN transistors. I noticed when using a NOT gate the voltage gets divided when ...
-3
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2answers
60 views

Why do RI=RL equal in maximum power transfer theorm?

I know mathematical proof I need explanation. Why this happen.That doesn't make any sense to me.I know that in series connection current (I)is same.But here  current flow is changing with different ...
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2answers
21 views

Step Response RC Circuit: Current at Capacitor

I have a problem understanding why is that ic=0 at t<0 if the switch is closed for a long and only opened for t=0? My friend told me that at t<0, the ic will always be 0A regardless whether ...
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2answers
68 views

Ohms to volts i [closed]

Hi I am not sure if I understand this! Ok if I have a power source of 5 volts which then has a resistor of 6ohms and another resistor of 4ohms in parallel with a volt meter would I add the two ...
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1answer
47 views

Voltage Drop on parallel resistor

I am trying to verify voltage drop across a resistor as seen on my multimeter with basic ohms law calculations. As shown in below circuit (from Electronics for DUMMIES). The multimeter shows a ...
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3answers
130 views

Are there gaps in the 2% resistor standard values?

I was reading the Wikipedia entry for E-series resistor values, and I decided to graph the values on a log plot. The plot shows the values nearly evenly spaced, which makes sense because adjacent ...
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2answers
50 views

Op-Amp decreasing amplitude of audio signal

For a final project for an electrical engineering course I am taking (my first), we have been tasked with combining input from a small microphone and an aux cord, amplifying it, transmitting it via a ...
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1answer
29 views

What resistors to use for 60, 8000mcd LEDs, with 4 * 1.5v battery source? [duplicate]

I currently have 60 LEDs in a parallel circuit. I am using 4 1.5v batteries as the source. The LEDs have a forward voltage of 3v-3.4v (8000mcd, wavelength 460nm). My questions are: Can I just use ...
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2answers
196 views

LED circuit is draining AA batteries REALLY fast

My question is long, rambling and weirdly specific. I hope I'm not violating like 50 stackexchange rules, but I'm completely lost. Long-time lurker, first time asker and pretty new to circuits in ...
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2answers
79 views

Creating a DC resistor network matrix

I have the following resistor network and I need to make a 7x7 matrix which would be the solution . I know the resistor values, but not the v1, v2, v3 or any of the current. I'm supposed to combine ...
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4answers
143 views

why would you ever put the resistor on the positive side [duplicate]

If a resistor is suppose to resist over current to the load through a cable in a series DC circuit then why would you ever place a resistor on the positive cable side instead of the negative cable ...
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0answers
26 views

Limiting 12V DC current draw on an absorption type camping fridge

I have a absorption type fridge that can run on 12V, 230V and gas. It is rated at 100 w but draws much more than the 8 or 9A that one would expect. When measuring the resistance through the 12V ...
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1answer
18 views

How to calculate resistor needed between generator and bridge rectifier?

I am almost done with constructing my railgun however, I am stuck with this last problem. To charge my 110 V 35 mF capacitors, I am converting 120 V 30 amp AC current from a generator to a 120 V 10 ...
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0answers
30 views

Diode-RC Circuit Differential Equation

I want to find the differential equation relating Vout to Vin, I'm stuck at a part in the derivation and was hoping someone could help. From equating i1 to i2 + i3, I have: [![enter image ...
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0answers
65 views

I2C weird values when two slaves are connected parallel? [migrated]

Alright I'm trying to connect two sparkfun ZX sensors that communicate to an Arduino Uno with I2C. When I connected each one independently to the Uno the Z and X values from the sensors seem fine. But ...
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2answers
96 views

What resistor values should I use for a voltage divider that has to operate at low temperatures?

I'm designing a flight computer for a lightweight pico balloon - it will (hopefully) operate in the upper atmosphere down to around -40C. To keep the weight down, the whole thing is going to be ...
0
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2answers
84 views

Resistor for 20 LED's in series

I am reverting here for some advice on a LED panel circuit that I am trying to build as I cannot find any concrete answers anywhere else online. My apologies as my understanding of electronics is very ...
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1answer
41 views

Voltage Mixer with 3 Resistors

The above is the requirement, I have configured a circuits as shown below simulate this circuit – Schematic created using CircuitLab I have solved the above schematic using ...
31
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8answers
4k views

Are two (or N) resistors in series more precise than one big resistor?

Let's say I have one 2 kΩ resistor with 5% tolerance. If I replace it with two 1 kΩ resistors with 5% tolerance, will resulting tolerance go up, down, or remain unchanged? I'm bad with ...
4
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3answers
156 views

I2C communication won't start unless SDA pullup resistor is reinserted

I'm working on a project where a PIC12LF1552 microprocessor is using I2C to talk to a TMP75 temperature sensor. Like the title says, a very strange issue keeps happening. Overview Every time I ...
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4answers
78 views

Purpose of Resistor - comparator

I am studying this time delay circuit and am curious to know the purpose of the 4.7kΩ resistor. As I see it, it has no purpose. I've built and tested this circuit with and without it and see no ...
0
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0answers
97 views

Location of the resistor, does it make a difference? [duplicate]

I have this very simple circuit: If the current is flowing from the - terminal to the + terminal, why is the resistor not on the other side? when I change placement of the resistor, nothing ...
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2answers
57 views

Arduino - Calculating Resistance

I am trying to connect an ESP8266 Wifi Module on a Pro Mini Atmega328 5V 16M Full Specs Here - Specs The Atmega328 pro mini outputs 5v on the vcc pin while the ESP8266 can handle max 3.3v. How much ...
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1answer
42 views

Do I need to connect a resistor to either one of the 2 input pins of this “and” logic component? If so, what would be the value for it?

The said component is sn74lvc1g08 from TI, datasheet. I was planning on connecting 3 1.5 volt AA batteries (in other words, 4.7 or 4.8 volts max in total) to one of the input pins (either A or B) and ...
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2answers
39 views

What will be the value of resistor to be connected in series with freewheeling diode if brake coil is 110 V DC

In order to quickly off the brake, what will be the value of resistor to be connected in series with freewheeling diode? Brake coil is 110 V DC.
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2answers
70 views

Calculating resistor for LEDs with different Forward Voltages in series

I need to work out what resistor I need for a series circuit containing 3 LEDs of 2 different types, and a 9v battery. I can do the maths, but I need to check I'm doing it right as I'm trying to ...
3
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3answers
509 views

How to convert 14V AC to 5V DC?

My interphone's buzzer receives an AC voltage of 12V. I would like to substitute this buzzer with an embedded board (raspberry-pi). What would be the ideal way of converting such voltage to 5V DC? ...
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2answers
77 views

How to make ammeter with arduino?

i'm interested to make ammeter from arduino. So, i have 70A/50mV shunt resistor and wiring it into arduino. From my schematic, Is this possible to meassure the current from 12V battery?If it possible ...
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1answer
50 views

diode and resistor in parallel with resistor

how do you calculate V\$_{R3}\$ in the circuit below? V\$_{in}\$, all the resistor values and the type of the diode are known. By simulating this circuit one can see that V\$_{D}\$ is increasing ...
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2answers
42 views

Capacitor Balance Resistor value

If you help to find out the right formula to calculate Balance Resistor and its power value( R1 and R4 ) as shown in Pic. because i have seen every one is using different different formuals. Data ...
1
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0answers
35 views

Pulse sensor: Choosing the right resistor for the phototransistor

I want to use specifically the SFH 309 NPN phototransistor in order to create a pulse sensor that works as seen below: The IR diode emits IR light to the fingertip from the one side and on the ...
0
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2answers
70 views

Can a single potentiometer be hooked up to multiple fans to control their speed?

I have recently learned about potentiometers and their "variable resistance" porperty. I am looking to hook up a Potentiometer in order to control 4 12VDC Fans. I am not sure if that is a good idea, ...
6
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4answers
567 views

SMD resistor maximum voltage: is 200V really a limiting factor?

I need a resistor to work with 230 VAC voltage. So 400V rating would be appreciated. However most of the chip resistor with size 1206 and above has only 200 Volts of maximum working voltage. Main of ...
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2answers
145 views

Reducing the AC voltage using resistors

I want to reduce 220VAC to 5VAC and using one 100K Ohm resistor and another 2K Ohm resistor. Two resistors are connected in series and measuring the voltage from middle of two resistors. I am happy ...
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1answer
45 views

How to calculate the resistors to convert 24V to 3.3V using a TCMD4000

I would like to convert a 24V signal to a 3.3V signal using a TCMD4000 optocoupler. Datasheet: http://www.vishay.com/docs/83513/tcmd1000.pdf How can I calculate the resistor's value on the input ...