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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32 views

Voltage help with resistor

Im using a 3.7V 18650 Li-ion battery (Ultrafire) and the circuit calls for a 27 ohm resistor. But one battery tested at 4V and the other 3.7V. Is the resistor too low now? Which rating should my ...
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3answers
99 views

Power dissipated in 0 Ohm resistor [duplicate]

I have seen many zero ohm resistors which says that maximum resistance is say 50 mOhm. But, the maximum current rating will be only 1 amps. 0603 package. Power rating they mention as 1/8 watt. Can ...
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4answers
281 views

Measuring a huge resistance on low voltage

I was thinking on this theoretical experiment for a while, but nothing useful came into my mind. We have a "resistor" (rather a material like plastic) with a resistance expected to be very high, say ...
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2answers
803 views

Unusual old resistor symbols identification

Image from: here. This image is the schematic of an old Tesla 521A valve amplifier radio. On the following resistors in the schematic there are weird markings: R4, R5, R6, R24, R25, R26 I am ...
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72 views

When to use a 1/4 Watt resistor vs 1/2 Watt resistor

I have never understood the difference between 1/4 & 1/2 watt resistors, and in all of my EE lab courses I have always just used 1/4 Watt resistors. When does one use 1/2 Watt resistors and what ...
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16 views

Power Metal Oxide Resistor - Maximum pulse voltage

I am looking for a suitable series resistor (220k) for a 230VAC optocoupler input. The device must meet requirements from EN60664-1. I am still trying to understand the final requirements, but from ...
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27 views

Proteus VSM: digital vs analog resistor and LED

I'm a newbie to electricity and electronics in general. I've been reading about the principles and have a basic understanding of them. I'm also diving into creating my first basic circuits with ...
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2answers
89 views

smd resistor and regular through hole resistor

My question is fairly simple. I am building an SMD LED board and i am limited in space. So originally i was planning on going with through hole resistors, but have it being i'm very limited on space ...
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3answers
60 views

pull down resistor in PIR circuit

I have an motion sensor circuit. The circuit calls for a voltage of 2-15 dc volts. On the PIR data sheet the source pins calls for a pull down resistor of 47K at 5 volts. My question is if I use 8 ...
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1answer
50 views

SPI Communication during Programming

I am using the ATtiny861a and have made it so that the SPI connects to a Radio and an external memory source VIA two different chip select pins but sharing the same MISO/MOSI/CLK line. Correct me if ...
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2answers
56 views

How to find the power delivered to the load?

I'm trying to solve a homework problem to find the power delivered to the 10Ω load. So far I found the total resistance, which is 12Ω. And I think I have the right formula to work out the power, ...
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1answer
67 views

Calculate values of resistors [on hold]

How to calculate values of R1, R2 and R3? R4 is a load 40 Ohms 300 mA. R3 is connected to ATMega8 output. hFE3 of DB136 and BD135 is 40
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68 views

Are these resistors in parallel?

Suppose I have the following circuit: Are resistors R1 and R2 in parallel, assuming that through resistor R1 flows current because this circuit is connected as a feedback to another circuit? And if ...
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44 views

Two cables, same resistance, different lengths, speed of current transfer

If I have two cables, with different size, but in total the same resistance, what will be the speed of the current transfer( how much time will it take the voltage to appear at the end of the cable). ...
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4answers
60 views

Need to extend bulb life on 13vDC, 100 watt headlights

I have a boat, that uses two 13V, 100 watt lights. The output from my alternator is running at 13.8V-14.5v and it is rated for 90 Amps. These lights run $270/pair and seem to burn out quickly. They ...
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1answer
98 views

Is it bad to have too little or too much resistance?

OK I need a 27kOhm resistor and I don't like shopping online. So, I was just wondering if it is bad to have a resistor with a too high or too low value. I was at Radioshack and all they had was ...
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2answers
395 views

Are there downsides to using resistors with too high power ratings?

I'm hoping to measure the current draw to my ESP8266 with a scope and a shunt resistor. I think a 1ohm resistor might drop the voltage too much, so I'm thinking to use a 0.5ohm (or even a 0.1ohm) ...
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78 views

why my LEDs burned with the right driver?

I am trying to connect, in parallel, 18 LEDs that have these specs: LED size: 10mm; Voltage: 3.2V - 3.4V; Current: 20mA. Driver Type/Model: MeanWell LPC-20-350 (datasheet: ...
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48 views

What is equivalent Resistor different Resistors put them in series or in parallel if they have a different wattage and different resistance?

What is equivalent Resistor of two this different Resistor put them in series or in parallel if they have a different wattage and different resistance? In practice somtimes we have a resistor with ...
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2answers
361 views

Purpose of input resistor in ADC circuit

What is the implication of the 1 Megaohm resistor in the schematics attached? Will I be able to detect the condition of the motor (running, not running, stalled)? Part information: MCU ADC (ADC ...
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1answer
42 views

How can I calculate time constant and charge time of RRC circuit?

This circuit is part of my time delay circuit. I want to calculate exact value of delay time. Please help me. simulate this circuit – Schematic created using CircuitLab
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1answer
35 views

4/5 band resistor - extra black band

I have two resistors which need to be replaced. I tried to determine the value, but it can't make sense of these black bands: For reference the bands are: brown - silver - green - brown - black ...
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177 views

Understanding a 2 transistor oscillator?

I asked a question here about why I was getting a sawtooth wave from a two transistor oscillator. While that question is answered, I don't understand how the circuit produces oscillation in the first ...
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1answer
36 views

LTSpice capacitor ciruit behaviour doubt?

I have basic knowledge of electronics and i have been using LTSpice to clear my concepts lately. I also have breadboard, multimeter etc. The first circuit i tested is a simple capacitor resistor ...
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1answer
81 views

2 NPN Transistor Square Wave Oscillator?

I have built the circuit found here. I substituted with 22K resistors at R2 and R3, and substituted C1 and C2 with .022uF capacitors. These are all the components I have lying around. Everything ...
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116 views

How serial resistors actually reduce EMI?

I am recently working with a GSM based system, and there was this advice in the datasheet of the GSM module: 22Ω resistors should be connected in series between the module and the SIM card so as ...
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1answer
49 views

Resistance across materials

I'm planning to use 2 PCBs to sandwich some conductive foam - to use it as a force sensing resistor (FSR). In order to tie them together and add them to a metalic suport I'll be using M4 metalic ...
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49 views

DC circuit theory: Equivalent resistance help

In the given DC circuit, I need to calculate resistance \$R_{2}\$: if the equivalent resistance between nodes 1 and 2 is \$R_{e}=100 ohm\$ I get the value \$R_{2}=36.36ohm\$ \$R_{1}\$ and ...
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67 views

Diode in parallel with resistor

SE, I've used the SE:EE forum search and several search engines internet and haven't found a single question similar to mine. But I don't think that it's that complicated, I'm just having a hard time ...
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1answer
21 views

Servo converting to continuous

i have 2 servos 7.2 volts,the rated current is 0.35 ampere and 3.5 ampere stall.i want to convert it to be continuous,so i will remove the potentiometer and put two resistors equal in value instead of ...
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32 views

Battery Cell Properties [closed]

I have a pair of Bluetooth headphones with a 3.7v, 180mA battery cell. I am wondering if it would be possible to increase the battery cell by replacing it with maybe a 5v or 9v. However I don't want ...
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1answer
34 views

Can I measure large force using series FSR?

Is it possible to measure large force using multiple Force Sensitive Resistors in a series? Will I have to stack the resistors up? Will the measurement be reliable if I place them side by side? I ...
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92 views

Voltage drop through a resistor using Ohm's Law?

I'm having a very hard time comprehending basic Ohm's Law. I was recently watching a video on the operation and use of Operational Amplifiers, and was completely lost because I couldn't understand ...
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45 views

How do I determine my burden resistor for my current sensor?

So I've got a -12v +12v ADC input limit and I've got a 200 turns ratio current transformer. My input Max current is 30A which is stepped down to 150mA. How do I determine the right burden resistor so ...
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42 views

CLL(Capacitor long life)capacitor filtering to reduce the current spikes

if we are using capacitor between the coomutation segments of brush dc moto then it reduces spark generation. as main function of commutation system is to reverse the current in the coil. by using ...
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1answer
123 views

Switching a resistor by software

I want to communicate with a microcontroller over a CAN bus which needs (ideally) 120 ohm terminal resistors at the end of each bus. I want to integrate this resistor into the circuit and activate it ...
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1answer
45 views

Three series LED arrays in parallel, resistor value?

i know this is possible but not sure how to work out the resistor value needed... I should point out that I am re-using a PCB that has had all the components removed. I need 15 LEDs in 3 parallel ...
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2answers
39 views

Question on Resistors for use with 5050 LED Strips

I bought a set of red and yellow 5050 waterproof LED strips for my motorcycle. I'm looking to add them to my topcase so it has running, brake and directional lights on it. Right now, there are no ...
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46 views

How many newtons could this BF350-3AA strain gauge support?

I am planning to purchase a strain gauge, the BF350-3AA in particular although there is no mention of how much force it is able to withstand. Also if someone could advise me of other strain gauges. ...
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1answer
71 views

Calculating feedback resistors for op-amp based voltage regulator

I need to design a voltage regulator with an output range of 20-25V. I managed to re-create this ciruit from a course, but I'm stuck on calculating resistor values. These are the formulas I'm given ...
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78 views

RF attenuator resistors

hi i am trying to find a formula to reduce 1 watt 1000mw to 0.5 watt 500mw RF basically cut the rf power in half using an attenuator which kind of resistors would be best for this has to be ...
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81 views

Resetting a counter when it reaches 6, without logic gates

I have a 3 bit ripple counter (using t flip flops) and I want the counter to reset to one when it reaches 7 i.e. the counter counts from 1 to 6. My idea was that I could hook the three outputs from ...
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4answers
59 views

Is the hfe of a transistor dependent on the resistance on the other parts of the circuit?

I have a circuit using a NPN transistor with a motor before it and a pwm into the base. The motors draws a current of 600mA if I plug it directly into the power source, just under the maximum allowed ...
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pcb trace current limitations

i did try some calculators but some of them is complicated and i've got lost i've a width of about 2mm and depth of 1-3mm, how much current could they handle ? what if i feed them more current ...
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2answers
63 views

What resistors should I use?

I have just started learning the basics of electronics. I found a circuit which uses NPN as signal Amplifier and powered by 12V source. The signal source is a audio from Mobile headphone jack. I ...
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2answers
59 views

surge limiting resistors for full-wave bridge rectifiers

I'm an electrician going back to school online to get my electrical engineering degree. I am having a hard time with some of the homework, as the book is extremely confusing, and does not always go ...
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1answer
46 views

Difference in Metal Film and Carbon Film

Hey all I have a WS2812B RGB LED strip that I am wanting to use with an Arduino. The directions HERE state that it's best to use a Capacitor and register in order to have smooth operation. So I went ...
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1answer
61 views

Can use 17 resistors with 16 rgb led's?

I always see an rgb led ran with 3 resistors, for example a 20ma led on 5v power uses 150ohm's for red due to it's lower voltage but only 100ohms for green and blue. I am running 6 shift registers off ...
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151 views

Max current for 0\$\Omega\$ resistor [duplicate]

What would be the max current an 0805 0Ohm 5% resistor can handle (5V-24V) ? Thanks for your answer.
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2answers
113 views

Is there a way to measure three discrete resistances simultaneously?

I'm working on a test box for fencing body cords. These cords are always 3 wires, and will plug into a box that I'm still designing. The test box I currently use connects to a multimeter and has a ...