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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42 views

Circuit Partial Failure

We are working on a circuit which appears to be failing during operation due to heat (putting a fan over it keeps it running). We have narrowed the possible parts down to a power resistor and a zener ...
4
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2answers
221 views

Weird 240 ohm resistor on zq line to DDR

I've been looking at schematics that interface ddr ram and noticed a weird notation for their zq pull down resistor. What is with the dot at the top as well as the 1%? Haven't seen this before.
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7answers
2k views

Is there such a thing as rubber band resistor?

I'm doing a project with some tight requirements, in which I need to measure the distance between two points, which might not be in direct view of each other, and on parts that are too small to mount ...
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0answers
37 views

Running a fan off minimal solar power [on hold]

I need a little help. It has been over 30 years since I last was in a high school electronics class. I have forgotten much. I have a solar panel. I found that in low light levels I can use it to ...
1
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2answers
52 views

High frequency rf resistors

I need non reactive resistors for use at LF thru HF (100KHz thru 30MHz) for use with radio receiving antennas as terminations. Carbon comp and carbon film work but have their shortcomings in stability ...
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0answers
104 views

Mosfet keep circuit closed (vape mod)

Hello i made circuit with IRLB3034 mosfet for using vape mod with low current rated button, but i have problem - mosfet is firing itself when i plug battery in and its overheating (coil is 0.5ohm). I ...
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2answers
94 views

Voltage Divider producing unexpected voltage

I am attempting to create a voltage divider that create 4.5 volts from a 9v battery. Using the voltage divider equation 4.7k / (4.7k + 4.7k) ) * 9v = 4.5v, I ...
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3answers
123 views

Why is the voltage across the capacitor constant?

I've connected a 6V DC voltage source via a 1Ω resistor to a 1F capacitor. I was expecting the simulation to reveal a less constant t-vs-v graph: it would start at 0 and after a while stabilize ...
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0answers
47 views

resistor finding [closed]

A 35V dc supply is connected across a resistance of 600 ? in series with an unknown resistance R.A voltmeter having a resistance of 1.2 k? is connected across 600 ? resistance & read 5v.the value ...
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2answers
39 views

Termination resistor creating communication problem in RS485 MODBUS/TCP

In RS485 communication, what is the role of termination resisotor. Is it mandatory? I have been working on a project with MODBUS/TCP over RS485 where upto 32 slaves are there in some links, out of ...
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1answer
62 views

Motherboard RGB diode control and resistance?

I've recently acquired a new motherboard for my PC which features RGB strip control. That's well and good but I have particular need to control a single RGB diode with that same header. The issue I'...
1
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6answers
188 views

Will electricity flow in a perfectly conductive medium

I was just wondering that since resistance is required for a potential difference to build up, what happens when we have a perfectly conducting wire, 0 resistance, will current still flow through the ...
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2answers
129 views

What kind of elements are these?

I disassembled a LED lamp and it's circuit. My intention is to rebuild that circuit within EveryCircuit app, to understand how it is working. On this circuit I found two elements that are rising ...
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3answers
125 views

Capacitor charge - why a resistance is needed?

I'm wondering why every example of a circuit capable of charging a capacitor has a resistor in it. Why is this resistor necessary?
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2answers
47 views

LCD cbc016002A29 backlight resistor value

I'm trying to connect a cbc016002A29 LCD to 5V, and the tutorial I'm following says: Next we'll connect up the backlight for the LCD. Connect pin 16 to ground and pin 15 to +5V. On the vast ...
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0answers
98 views

Simple resistance based water sensor works in stagnant water but blows out in running water, under faucet

The circuit is intended to flash an LED every 7 seconds when there is no water and to flash it very rapidly (time period less than 1 second) when it "senses" water. It all worked well when tested with ...
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2answers
108 views

How to ignore pulse in a circuit

I have a 12v cable that sometimes pass (75%on-25%off) and other times 100%on. What can I put on that cable so if the input is (75%on-25%off) then the output is 0v, and if the input is 100%on the ...
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2answers
50 views

Input resistor to BJT base > ground resistor, why?

Thank you for your time. I'm new to electronics and so this question might, to you, call for an evident answer. Nevertheless, I can't seem to find that answer. I've stumbled upon a schematic for a ...
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0answers
44 views

Effect of damping resistor on its upstream?

I am struggling on understanding how certain function of circuit part affect inside whole circuit. There are two electron sources: 1. electrons generated from ionization by discharge (Plasma), 2. ...
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1answer
65 views

How to turn a DIP switch into an array of logical values

Is there a better way to turn a open/closed switch into a logical value (capable or sinking or sourcing current) other than: simulate this circuit – Schematic created using CircuitLab I'...
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0answers
57 views

Circuit to measure impedance

I'm trying to make a circuit to measure impedance through a FRDM-KL25Z board. The basic idea is to use two signals to calculate the phase shift between them, and use a impedance divider to calculate ...
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2answers
52 views

I have a circuit with a 9V battery, followed by 3 10 ohm resistors, and an led all in series…?

simulate this circuit – Schematic created using CircuitLab I have a circuit with a 9V battery, followed by 3 10 ohm resistors, and an led all in series. The led has a forward voltage of 2.5V ...
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3answers
82 views

Troubleshooting LTC4150

Earlier today i changed the value of the shunt resistor of my LTC4150 coulomb counter from 0.05 ohm to 0.5 ohm to get more precise readings.In the datasheet it was specified that voltage drop of the ...
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3answers
57 views

Find v1 and v2 of a summing amplifier when it is in series with another Op-Amp

There is a summing amplifier with two AC power sources (v1+v2,) each connected to a different Ground. Each of these sources connect to a resistor (R1+R2,) and then to a summing point, which branches ...
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1answer
47 views

Find the total resistance of circuit with both series and parallel resistors

I found this circuit in a textbook, but I'm having a difficult time calculating the total resistance here. I tried using the formula for parallel resistors with the 3 resistors the the upper left, and ...
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1answer
48 views

Series-parallel RLC resistor voltage

simulate this circuit – Schematic created using CircuitLab Edit: Impedance value below has been found incorrect and would apply to a purely parallel circuit instead. Question has been answered ...
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1answer
32 views

Is There a Symbol for an Inrush Current Limiter?

Is there a schematic symbol for an inrush current limiter, or is a resistor used instead?
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2answers
90 views

Pull down resistor on logic gate input

I would like to use a pull-down resistor on the input of a NOT logic gate. I am using a 5V microcontroller, and I want to ensure that the input of the gate will never be floating (eg. microcontroller ...
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1answer
40 views

Calculate base resistor of PNP transistor in switching circuit with variable resistance

I would like to read analog input on my Raspberry Pi using various resistive sensors I represent in the schematic below as potentiometers (R5 ad R7). I need to be able to switch the circuits on and ...
3
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4answers
492 views

Selecting passive components [closed]

I am in the case where I read a lot of datasheet and I quite often see some circuit where the chip manufacturer indicate some value for resistors and capacitor but by not indicating any part number, ...
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2answers
120 views

how to calculate voltage drop by a resistor/ circuit attached parallel to another resistor/ circuit?

On my battery eliminator, if I measure source voltage without any load, it gives the correct voltage. But when I add a load, the voltage drops. And if I short-circuit the 2 output-leads with a ...
0
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2answers
49 views

Understanding pull-up resistors and the 7489 memory chip

I have been learning about the 7489 memory chip. I had two of these that turned out to be broken (see here for previous question on this). I got more and I have finally gotten everything to work. ...
2
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1answer
98 views

Using an array of resistors to give priority on a bus

I remember that the ZX Spectrum used an array of resistors to let the output from one chip override the output from another chip (on a bus) when both had the ¬oe pulled low. ...
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1answer
161 views

Why is the voltage across a Zener diode so dependent on current?

I was going to use a 3.3V Zener diode to protect the analog inputs of an Arduino Due, but I found that the voltage drop across it was only 2V. So I tested connecting it to my power source with a ...
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2answers
86 views

Zero Crossing Circuit Input Resistor

I'm building a dimmer, and got some questions about the resistor in the zero cross circuit. My circuit is like the image above, and I'm wondering if in the case of 100V input the current is to ...
0
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1answer
59 views

Max handling power for a 10w speaker resistor [closed]

I have been told that a non-inductive or inductive resistor used for speakers can only handle 10 watts if it is a 10 watt resistor, which makes no sence because they do use even 5 watt resistor in a ...
0
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1answer
66 views

Can you explain how the following garden solar light circuit works?

I found the following circuit in a solar garden light. The cut off white and black wires are from the solar panel. What does the 4 pin transistor do?
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1answer
44 views

ambiguous component values (ex. U01 U47 M47 etc.)

i'm having a hard time understanding components value when it's given in the following formate U01 U47 M47 sometimes it's even worse like 4N7 i know that U for micro, M for mega, N for nano but i ...
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2answers
67 views

Unexpected results when trying to amplify voltage across a wheatstone bridge

I am working on a project, and am trying to amplify the voltage across wheatstone bridge. Here is the diagram: where \$R_1 = 1,000 \Omega\$ \$R_3 = 10,000 \Omega\$ and \$R_2\$ is a potentiometer,...
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1answer
92 views

Solving a source free series RLC circuit

How do I proceed to solve this problem. If I write a KVL equation, I get $$4 (4 Vc) +1/10^-3 integral i dt - 10=0$$ What to do next?
2
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2answers
60 views

Closed circuit vs low resistance resistor

I'm learning electronics and this confused me. In this circuit it shows that current flows through both wires with resistors and lower only through one wire where there's no resistor (even though one ...
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2answers
90 views

How does Current relate to Voltage in their behavior in our physical world [duplicate]

I'm really an electrical noob who tries to understand voltage, current and resistance. I know the formulas and can somehow come up with basic explanations about the physics of electricity. However, ...
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0answers
32 views

Finding the current through resistor in source free parallel RLC Circuit for t>0

My solution: Since alpha >w0, so response is overdamped. Current through inductor:$$ Il(0-)=Il(0+)=6 $$Voltage across capacitor: $$Vc(0-)=Vc(0+)=0V$$ Current through resistor: $$ Ir(t)=A1e^{s1t} + ...
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2answers
74 views

A question about E12 series resistors

I'm trying to calculate E12 resistor series myself. Above is an illustration of the idea where such equation can be written: x = r3 + r3 * %tol = r4 - r4 * %tol form that we can derive: r4 = r3* [(...
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3answers
106 views

Is this a power resistor?

I'm trying to repair an electrophysiology amplifier (AXOPATCH 200A). It has this power resistor which I desoldered because I suspected it was broken. The color code (red, green, black, gold) gives 25 ...
0
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2answers
46 views

How were values of Vc(0+) and i(1.5ms) found?

I get that by applying source transformation, we get a (0.1*200=20 V) source but shouldn't 0.1 A current be divided into 50 ohm and 100 ohm resistance? Also why i=0 at t=1.5ms?
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1answer
72 views

Resistance of twin core wire

I'm trying to do a problem for revision and I'm running into problems calculating the resistance of this circuit used to approximate a twin-core wire. It's used later in the question with the middle ...
0
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3answers
105 views

How was this equation for finding current written?

It doesn't make any sense because at \$t\gt 0\$ the two circuits are disconnected (the left and right portion). How has \$25 i_x\over 20\$ been calculated?
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1answer
44 views

Ethernet driver Circuit

I've been working on Ethernet schematics, i noticed a network of capacitor and resistors present outside the RJ45 connector. For what reasons these passive components are used? I've attached the ...
0
votes
1answer
57 views

why add a resistor parallel to voltage source? [duplicate]

Sometimes I see a resistor parallel to voltage source (such as image below), isn't it completely useless ? Edit: I see the other similar question now, but I think it doesn't have the right keyword ...