Questions tagged [resistors]

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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3answers
56 views

Using shared pull-down resistor or providing pull-down for each mosfet

There are some P channel and N channel mosfets which operate as swiches in figure 1. Also, there is a pull-down resistor for each mosfet which prevents the mosfet's gate being float when the VCC is ...
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2answers
103 views

Why does the TCA8418E datasheet ask to connect all pins to Vcc using a pullup resistor?

I am trying to use the TCA8418E I2C Controlled Keypad Scan IC With Integrated ESD Protection. On page 3 in the pin functions table it says to connect SDA and SCL to Vcc using a pullup resistor. Do I ...
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1answer
75 views

Why is there a high value resistor between source and gate in this p channel mosfet?

I am trying to understand practical uses of mosfets and came across the circuit from the image below. The PWREN1# is active low,and comes from a IC that is being powered by VCC5V also. So I know a p ...
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1answer
115 views

Reading wrong values from GPIO when connected with a 1 MΩ resistor

I'm trying to re-implement the Arduino Capacitive Sensing Library. In the process, I need to read one GPIO's state with another GPIO. The board I'm using is a ESP-01S with the ESP8266 microcontroller. ...
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2answers
74 views

Safe to run a 1/2 watt resistor at 0.4 watts in enclosed housing?

I have a circuit that dissipates 0.4 watts through a 1/2 watt resistor. It gets quite hot to the touch. Every other component in the system is cool. I am just trying to make sure this is safe in a ...
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1answer
49 views

Calculations relating to carbon film resistor

Im researching on carbon film resistors and film resistors in general, hence I would like to know certain things: Resistivity of carbon the film is made-up of? Does the resistivity depend on the type ...
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1answer
59 views

Why does the RC corner frequency change when replacing the resistor with an equivalent diode?

This is slightly related to another question but actually a matter of its own: This is a simple analysis of the corner frequency of an RC lowpass formed by resistor R1 and capacitor C1, for various ...
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0answers
88 views

What determines noise spectral density of diode-resistors?

One common way to think of a diode is that it is a variable resistor, whose resistance depends on its voltage drop and can be controlled via its bias current. I have two questions about how far this ...
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1answer
60 views

Precision resistor measurement [closed]

I have received the data pack for 0.05 ohm +/-0.1%. How should I read the measured resistance values by the provided RC1 and RC2 (resistance record) ppm?
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1answer
35 views

Relay driver with Zener cutoff

As seen in the schematic, I need to control a relay using two voltage sources. The relay goes off when source Nr.1 (4.2V) is less than 3.6V AND when source Nr.2 (7.4V) is less than 6.8V, by the effect ...
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1answer
74 views

Please help in the steps of finding Rth and Vth in the following circuit

The answer is Vth=0.839 V and Rth=3.77 ohm but I can't get the right answer. Please give me the steps to find it. what i did to find Rth: removed RL and 6V, 6 & 8 ohm are in parallel, which gives ...
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0answers
88 views

New resistance calculation after increasing wattage

I have some small lights in series (similar to the ones for Christmas,) normal ones not LED. They are powered with 3 batteries of 1.5 V and in series there is a resistor of 7.5 ohms (1 W I believe.) I ...
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1answer
92 views

Explain this tiny circuit (2 LEDs in parallel)

Please excuse my schematic. This is a tiny PCB near the DC5.5 Jack port of a laptop power supply. The transformer is broken so I dismantled it to learn some. The transformer reads like "220VAC ...
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2answers
98 views

Can I temporarily use normal resistor in place of fusible resistor

I have SMPS that uses 10 ohm 1W fusible resistor. I have located a fusible resistor in Amazon and its gonna take a while to deliver. I would like to know if I can temporarily use 10 ohm resistor for ...
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1answer
71 views

KiCad leave room for optional through hole resistor on top of default SMD?

I was wondering how one would go about creating a footprint for an SMD resistor leaving room for a through hole one to be soldered on top should one wish to adjust the value, a bit as seen on this PCB ...
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9answers
8k views

Why don't LEDs have built-in resistors?

A night of struggling to fit 16 current limiting resistors into a small breadboard for a uni project made me wonder why LEDs don't have any kind of internal resistance? I can't think of any downsides. ...
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2answers
76 views

Non-inverting amplifier with voltage offset question

I have come across this op amp configuration which will bias a 5 V peak-to-peak input signal so that it will lie above 0 V, (OP1.2 in picture), however I am having a hard time understanding how it ...
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2answers
84 views

Could I use a resistor rated for 1000w in a 1w circuit? [duplicate]

I am learning about resistors and may not understand something fundamental, but are there any reasons to prefer a low wattage resistor over a high wattage one? Other than space & cost, are there ...
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0answers
24 views

MCP73871 Battery Charge Management Board programming resistor question?

I am trying to get round the design flaw in a DS3231 real time clock module where it constantly charges the battery. https://forum.arduino.cc/t/zs-042-ds3231-rtc-module/268862/32 I was planning to add ...
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1answer
62 views

Astable Multivibrator using BC549s not oscillating

I just recently started learning about electrical engineering stuff, and since my final goal of building a Z80 Computer seems a bit far away, for now, I decided I'd make a simple clock I could ...
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1answer
65 views

Calculate total resistance. (Circuit analysis)

How do I solve this circuit and determine the total resistance between A and B if all the resistors are 120 Ω? Thank you.
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2answers
65 views

What does the RZQ stands for?

While manually configuring a Memory Interface Generator in Vivado, I saw an option related to the output driver impedance. There were two options selectable, RZQ/6 ...
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2answers
113 views

Why would these two resistors make a parallel connection?

The circuit on the left is the one that is given and the circuit on the right is the way that I visualize the circuit. Could someone explain why the equivalent resistance would be 5kΩ?
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0answers
96 views

Designing a push-pull amplifier

The exercise is to calculate \$ R_1\$, \$ R_2\$ and the gain for small signs of the following circuit, which is supposed to be a audio amplifier: And I have the following information: \$ R_L = 8\...
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0answers
102 views

Making easy 12V 100Ah battery charger circuit at home

I need a charger for a 100Ah battery and decided to make one. Now I need to order components and am asking for some help. I'm following tutorial at this website. Here is the circuit: I'm curious why ...
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2answers
246 views

How do I transfer this circuit to stripboard?

I want to construct this circuit because it look worth to try. However, I am not sure about connection between the components. This is the components placement that I tried, does it make sense? Please ...
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3answers
46 views

Thin Film Resistors, Deposition On One Side, Parasitic Capacitance if Resistor is placed such that Deposition next to PCB Ground Plane

I have a question for all high frequency and RF electrical engineers. Thin film resistors have a vapor deposition of resistive material on one face of the component. Let's presume that the resistor ...
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1answer
52 views

Calculate resistance of a grid starting from equivalent resistance

Considering the attached picture how is possible to calculate single resistance value (R1,R2,R3,...) starting from equivalent resistance derived from nodes A-A', B-A', B-B', B-C', ... Consider that in ...
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0answers
72 views

Confirm resistor and transistor for amp fix

I got the magic smoke on day 2 of using an 80s Yamaha A-500. Thought it was the large electrolytic caps as they'd leaked but on replacing them with Nichicon ones, the smoke continued on powering up ...
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1answer
58 views

what is the real electrons flow of a current source diagram [closed]

what is the real electrons flow when a current source symbol drawn .In arrow way or other way
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1answer
77 views

Quick equivalent resistance question [closed]

I have an equivalent resistance question. Is it possible to find the equivalent resistance of this circuit? I would like an explanation on how one could go about breaking this circuit down further to ...
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1answer
45 views

How to calculate wattage for gate/base protection resistor for a TRIAC

I am working on a project using the following circuit, which uses an Arduino type microcontroller to do pulse width dimming of AC circuitry using a TRIAC: I am wondering what wattage I should choose ...
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0answers
67 views

How to calculate resistors for an optocoupler?

I am a self-learner (for now) on electronics. I am trying to understand how to calculate resistor values when using an optocoupler and an ESP32 For my little project I want to sense several 220v wires ...
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1answer
74 views

Can pull-down resistor be connected before the gate resistor?

I noticed I have made a mistake in one of my PCBs and have connected the pull-down resistor of a MOSFET before its gate resistor (point A), rather than to the gate directly (point B, see schematic) as ...
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2answers
58 views

Fan humming sound when decreasing speed with a dimmer [closed]

I am using a ~large 400mm wall mounted metalic fan (specs below). I wanted to decrease the speed (and noise) with light dimmers (I tried 2 models so far) but when speed is decreased it makes humming ...
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0answers
36 views

Discrepancy between calculation and simulation

I am trying to implement resistors with switched-capacitors (SC). Consider the circuit below. SC can simulate a resistor by repeatedly charging and discharging a capacitor. Clocks clk1 and clk2 have ...
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2answers
212 views

Identifying unique color code of non-inductive wire wound resistors: Weird resistor color coding, never seen before

Here we identify the color code determining the values of non-inductive wire wound resistors, specifically Yageo's NKN series (but applicable to other manufacturers of this class), which are a unique ...
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1answer
73 views

How to calculate for the voltage across resistor R4 and R6 using the operating point values? [closed]

This is the schematic diagram for the circuit that I need to solve. All I need to know is if it is possible to solve for the voltage across resistor r4 and r6 with all the given operating point values....
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0answers
65 views

Identifying another resistor

I am working on finding a replacement resistor but am not entirely sure about the code. I am thinking its a 37 Ohm but would like confirmation. Thanks.
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1answer
104 views

What resistor is needed to discharge a capacitor of about 3kV (inside a microwave)

I've already made a capacitor discharge tool for a 300V capacitor and works fine using the 2 resistors that were on the PCB with the capacitor. I need to upgrade this to discharge a microwave ...
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2answers
100 views

LM317 is dissipating too much power

I used an LM317 in my circuit to get a regulated 1.5 volts output from a 3.7 volt battery using two resistors (220 and 60 ohm.) It worked fine, but the circuit dissipated too much power even when not ...
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2answers
51 views

Power absorbed by diode in simulation

This is a simulation in LTspice. The graph below shows the power vs time for diode D2. Is it a concern that in the first few microseconds, the power absorbed by diode is 500W? Is that a lot and will ...
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2answers
101 views

AC to DC rectifier (get the best efficiency)

Hi readers, this is an AC to DC converter. I have been trying to build a power-saving rectifier by changing the capacitance for this specific load (20 ohms and it is a constant load) in order to ...
0
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3answers
135 views

AC to DC converter circuit

This is an AC to DC converter. From what I have simulated in LT spice software, when the R1 drops from 1k to maybe 5 ohms resistance, the output is oscillating and no longer smoothing to DC. I have ...
2
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1answer
63 views

What are the possibilities to increase temperature of resistive wire?

I recently got stuck on heating up a resistance wire. I have 80cm long resistance wire (from hair dryer) that I need to heat up to about 160°C. Currently I have a battery pack that produces 33.6V DC ...
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1answer
48 views

Is this 240W power supply constant? [duplicate]

I want to buy this. However, I am not sure whether 240W power supply that I choose will efficiently power a 12 W device. Is the 240 W power supply constant or can it change depending on the power ...
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4answers
99 views

Reduce power output of 240V Ac supply by high resistor?

Main supply of 240V socket and connect in series with a very high resistor and a mini 5V 2A (AC motor). The reason is the high resistor would absorb a lot of the power supplied by the main 240V socket ...
0
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1answer
29 views

Correct values for current limiting resistors for motor driver (DRV8834) control lines

I would like to control a DRV8834 Dual-Bridge Stepper Motor driver in 'indexer' mode, where only two digital lines are needed (M1STP or STEP_BENABLE and M1DIR or DIR_BPHASE in the image below). ...
1
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2answers
48 views

Reason for a EAGLE "tRestrict" (no copper pour) layer under SMD/SMT resistors

I am designing a PCB in EAGLE. In this PCB, the major heat sources are my SMD/SMT resistors. I learned that a general principle to dissipate heat from PCB components, is to place thermal vias ...
0
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0answers
50 views

Can we look at only the voltage specification of a product? [duplicate]

I saw this specification in the product I wish to buy. Does that mean if I connect a 12V voltage supply from a battery, the current will actually be 5.8 A by default since the resistance of the device ...

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