Questions tagged [resistors]

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

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Highest Attenuation with Unit Resistors?

What is the most efficient unit resistor arrangement for high ratio attenuation ? For example, if I want to attenuate a (voltage) signal by a large factor (e.g. approximately 1000x), I could use 999 R ...
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my cooling pad is not working can anyone help me? idk bout any electronic stuff [closed]

**so the problem is I bought cooling pad around 6 months ago and it was working perfectly fine but today when I started it it was working normally but soon after it stopped working than I unplugged ...
105 views

How to design digital rheostat that can handle 100 mA?

Specification: Bidirectional current Output current: 1 uA to 100 mA Terminals common-mode voltage: +/- 12V That would be 24 Meg to 240 Ohm if that is possible. Stability: +/- 1% if possible Bandwidth:...
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Adding Resistor to Match Power Draw for Fan Replacement

I'm replacing a 12V 0.23A fan with a 12V 0.06A fan and want to keep the power draw the same. I believe there is load-sensing at the power supply side, which detects lower draw and shuts down due ...
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160 views

How does this simple circuit work if the diodes are replaced by LEDs?

How does the simple circuit in the answer to What is the simplest and best device (or circuit) to stop the flow of current in a line when current in another line is present? work? What I don´t ...
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I need to add some wirewound resistor in series with a voltmeter to make it high range. I am converting the voltmeter from 300 V FSD to 900 V FSD. As per my calculation the wattage should be 20 W, but ...
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What happen if both sides of LED connected to positive?

Question 1: If we connect both ends of an LED to the positive terminal of a battery, will it create a short circuit and damage the LED? Question 2: If connecting both ends of an LED to the positive ...
128 views

Why does a 230V 16A socket supply only the needed current to loads? [duplicate]

If I connect a 150W laptop charger to a socket that supplies at home 16A 230V, it will only draw the necessary amperage needed for the laptop charger at 230V. Why? Why doesn't my charger simply draws ...
62 views

RC series analysis with H parameters model

I'm writing this just to be sure I understood well the process of analysing a circuit with the $H$ parameters model. In this case, it is a very simple example of application; the circuit I'm ...
119 views

Identifying a component from an Acer Aspire F15 Laptop

I am currently working on a Laptop for a client, I have identified this part as a potential cause of the failure to boot, yet I have no Idea what it is?, what it does?, how to test it properly, and ...
91 views

Cant figure this out [closed]

Below circuit pulled from homemade-circuit.com, Practical Voltage Regulator Project with Feedback for Enhancing Output Accuracy, https://www.homemade-circuits.com/simple-voltage-regulator-circuits-...
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How to find current for Thevenin equivalent circuit

I'm trying to figure out how to calculate the Thevenin equivalent circuit for a voltage divider like the following one: I understand that V_th is obtained by opening the terminals of the output, so ...
539 views

Can we find the equivalent resistance just by using series and parallel combinations?

Can we calculate the equivalent resistance between $A$ and $B$ by using just the concept of series and parallel combinations$?$ I can solve this by assuming that a battery of voltage $V$ is ...
70 views

Does the rise time equal the decay time in a DC LR circuit?

The time it takes the voltage to decay from its maximum to zero after the switch is closed is ≈5$\tau$. I was wondering, does the same applies during de-energizing, i.e, when the switch is connected ...
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1 vote
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Resistor after voltage divider changing the maths?

I would like to get the correct voltage value after a voltage divider. In some way R7 is affecting the estimated voltage output value but I don't know how. My math, (Vout) calculated after R7: Vout = (...
58 views

Battery draining and resistor question [closed]

Say I have a motor that uses 9v @400ma, but it's powered by a 12v battery. I 'd use the ohm law and get a: 7.5 ohm resistor. But, as soon as the battery is being drained, let's say now the battery is ...
1 vote
63 views

DigiPot Actual Resistance Range?

I'm currently looking at a the AD8400 digipot: I'm guessing that the minimum resistance is determined by the wiper resistance? But besides that, does it mean that worst case, my digipot will have a ...
186 views

Find the equivalent resistance between $A$ and $B$ [closed]

In the figure shown below, find the equivalent resistance. I know I should add my attempt but I don't know how to approach these type of problems. This isn't the standard series-parallel combination ...
123 views

How do you approach problems like these where we have to find the arrangement of resistors?

Is there any specific methodology to approach them or is it just intuition? Because I am finding them really hard.
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Relay module I/O pins resistor

I'm making a project with a 12v relay module and a AC motor. The circuit is simple and doesn't need any microcontrollers. I want to control the motor using a relay and a float switch. I was hoping can ...
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What are the values of these resistors?

I have tried looking at various guides but there is nothing to indicate which way round the top resistor is. The brown bars on both ends are too similar. How, in general, can you tell whether they are ...
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Proof showing thermal noise of 2 resistors in series behave as a single noisy resistor

For the second part of this question, I came up with two slightly different answers? I believe it's the second one however I am not too sure which one would be the correct one. First one: Second one: ...
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290 views

How does this boost converter circuit work?

The circuit appears on this site in Post #45 by Michal Podmanicky. It is posted so that I can understand how the circuit works. It is not explained fully in the posted link. How does this circuit ...
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Output voltage didn't change after adding capacitors and resistors

I'm building a power supply that consists of a Type-C female to DPI adapter and a LD1117 voltage regulator (on a perfboard/protoboard). I was advised to add capacitors and resistors. Before adding ...
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Feedback of amplifier

Would just like to know, why on the first picture RE1 is "part" of the feedback and is RE3 not? Then on the second picture is RE part of the feedback as well? Is there any way generally how ...
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Strange Resistor Situation

I am looking at a schematic for an RF sensing switch, and I notice that there are two resistors that are marked in the schematic as 18 Ω resistors. They are 2512 SMT types and are installed in ...
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Saving my resistor [closed]

Does it matter if you put 2 different resistors in parallel and how would you keep the lower rated resistor safe if you know the power output is greater than resistor can handle? Edit: I'm using 2 ...
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1 vote
73 views

Are multiple SMD Chip Resistors in Series as Safe as a Wirewound Resistor for Mains Voltage?

I realize SMD Chip Resistors are not recommended for Mains Voltage and it's no wonder since their maximum voltage rating is lower than 100 V. I also understand that WireWound Resistors are recommended ...
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BJT circuit questions

I have landscape lights. The load is 3 VDC 100 mA for each filament. I have two of them so the load is 200 mA at 3 VDC. I have solar panel which varies voltage from 0 V to 1.5 VDC. I want the ...
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1 vote
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Sourcing a resistor

I'm looking to replace a resistor in a 300w + 300w Mosfet amplifier. It's the one in the photo and while I'm happy removing the old component and soldering in a new one, I'm not sure where to start ...
39 views

Troubleshooting Voltage Sensing Issues in Buck-Boost Chip Simulations

I performed a simulation on a buck-boost chip (LT8390). I understand that the sensing resistor placed between LSP and LSN is supposed to sense the differential voltage. This voltage is then amplified ...
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Selectively Activated External Circuit for ADC Measurement

I'm looking for efficient yet simple-to-integrate solutions where analog signal outside of microcontroller's range is being measured (e.g. 12V power supply) and measurements are done selectively. This ...
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I'm using a component tester to measure a resistor which I have removed from a circuit. The tester gives a reading of around 0.46 - 0.50 Ω. I have 7 other identical resistors (in circuit) and they all ...
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Selecting resistor value for PWM LED driving

I want to create a circuit to drive some LEDs with PWM. The circuit consists of a PMOS switch at the high-side and the gate driven by the MCU PWM pin that is configured open-drain. The LEDs have ...
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Did I draw this circuit diagram correctly for 2 MOSFETS? [closed]

Did I draw my circuit correctly? My project consist of one 5 V solenoid (but uses 3.3 V), one voltage regulator (5 V to 3.3 V), one diode, two N-channel MOSFET transistors, and one 5 V LED strip all ...
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36 views

Locating the temp sensor on motor controller

I am helping my neighbor with fixing his out of warranty EV UTV. I have narrowed it down to a faulty temp sensor. -Controller: Curtis 1234SE 72vdc 3Ph VFD. Fault code:15. What would a label next to it ...
42 views

Current limit resistor calculation zener diode

I designed an overvoltage protection circuit. My input voltage is 90V, and I need overvoltage protection at 90V. However, I used a 91V zener diode in my circuit. I have a problem calculating the ...
92 views

How to calculate resistors on PCB for white LEDs [closed]

Thanks for closing my post... once again. Instead of helping it gets instantly closed. I somewhat got the answer thanks to AnalogKid's answer! I dont get how he calculated the 2mA but thanks to his ...
112 views

Step response of a tricky RC circuit

This question was asked in an interview. The circuit is given below. The initial voltage across the capacitors is 3V each. Need to plot Vx vs time. My response is given below. But the panel told my ...
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Sensing Resistor in Buck-Boost controllers

In the LT8390, there are two sensing resistors. The one connected to LSN/LSP is called RSENSE(Buck), and the one connected to ISP/ISN is called RSENSE(BOOST). To illustrate this more clearly, I've ...
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Why does this vintage DRAM chip enable circuit require such a beefy resistor?

This is a small part of a mid-1970s chip enable circuit for a set of DRAMs. The DRAMs are TI's TMS4060 part (aka the Intel 2107 aka several others), and are 4096x1. So a typical bank requires 8 of ...
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current transducer Burden Resistor configurations

How will the current flow? Will it go from x1 to gnd and x2 to gnd---(Rb=30ohms) or x1 to x2 and x2 to x1 (Rb=60ohms) and when no current is flowing r1 and r2 will act as an pull-down resistor so ...
2k views

Role of a resistor in a specific, simple circuit

i am currently reading "make:electronics" from Charles Platt. On page 129 in Figure 3-87 i found a circuit, which i have reconstructed in the following image: The circuit is supposed to do ...
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Why don't these resistors affect the gain in voltage divider bias?

Our textbook says that voltage gain is not affected by the R1 and R2 resistors, but I don't understand the reason behind it. Also, don't we get the 1/gm that is in the denominator from r(pi) resistor ...
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Identifying resistors

I have these resistors that I feel are not clear in how to read their resistance value. My electronic hardware experience is limited but I have played around with Arduinos and Raspberry Pis a little ...
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Using small value resistor as a jumper connection

I made a PCB layout where I was planning on using a PCF8575(U7) with 74HC14(U10) logic inverter and ULN2003A(U8), but it wasn't working as expected so I want to swap the PCF with XL9535 or PCA9535 and ...
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Can we make 300 ohm 300 watt resistor from three 100 ohm 100 watt resistors?

We have three 100-ohm, 100-watt resistors, but we need a 300-ohm, 300-watt resistor. Can we create a combination to achieve this? We aim to dissipate 150 watts through the circuit. If I connect three ...
33 views

Why is pull-down resistor on low-pulse triggered relay input not working?

I have a low-pulse triggered latching relay board (datasheet for individual relays, link to board). Whenever I plug-in, or un-plug my Arduino Nano's USB cable the relay changes state (sometimes ...
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