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}\$)

learn more… | top users | synonyms (1)

0
votes
1answer
32 views

Should I care about IC input pin current?

When dealing with IC input pins, should I care about current flowing through the input, or is it the IC's responsibility to limit the current in its internals? The situation I am thinking about is ...
0
votes
4answers
48 views

Logic-level switching 12v

I implemented the following schematic trying to follow Jon Watte's reply to this question. There are two things I don't understand: Why is the probe Q14 showing 4.34 volts? Why is it not closer ...
0
votes
2answers
86 views

Why is the red diode in my RGB led burning out?

I have been working on a simple circuit that uses a 10mm RGB led. I have had the same problem again with the red diode dying out after maybe a day. This time I thought I fixed it, but I guess I'm ...
0
votes
1answer
34 views

Constructing an MCU controllable resistor

I need a resistor that I can control with an MCU like an arduino/raspberry pi. Ideally with 1M max resistance. The resistor will handle an analog signal range of \$\pm\ 9v\$. I've considered using a ...
2
votes
2answers
98 views

Help to join 3 resistors in parallel into 1 (power equiation?)

I want to join 3 resistors connected in parallel into one. Like this If for the total resistance I use Rt = R/3 But what about the power of them?
0
votes
1answer
61 views

PCB Current Shunt Design

I want to use a shunt resistor to measure the current flowing though a section of my circuit. I am deciding between using an off the shelf shunt resistor or simply drawing a wide track on my PCB and ...
3
votes
1answer
64 views

How does this sample and hold circuit work?

What role does the 30k resistor play in the LF398? How would that resistor eliminate any offsets introduced by the op-amps in a circuit like this one: On this ...
0
votes
1answer
25 views

linear actuator internal resistors

I have been trying for nearly a week now to try and build a mechanically locking box. I thought I could try using a linear actuator to do this, so I found a model I liked. My question is as follows: ...
0
votes
5answers
149 views

Why the resistor is not considered?

Why in the following solution the 6Ω resistor is not considered?
0
votes
2answers
69 views

Linear voltage controlled resistor divider

I'm working on an audio amplifier project and I'm trying sort out the solutions to certain problems. The problem that I most need to get solved is that I want to digitally control certain operations ...
3
votes
2answers
68 views

Bridge rectifier - min. required protective resistor

Looking at the datasheet for a MYS80 bridge rectifier, at the bottom it states Min. required protective resistor is 8 ohm. I could not find much information about a protective resistor in regard to ...
-2
votes
0answers
54 views

What resistor would be needed before two LEDs in series?

I was wanting to use the lowest amount of amps in my project because it contains around 60 LEDs. http://www.rapidonline.com/pdf/55-2484.pdf : The technical description It has a max current of ...
-2
votes
1answer
91 views

Please help with identifying this resistor [closed]

I'm trying to identify an overheated and failed component and keep coming to a dead end. The unit is a small rechargeable inspection lamp, it is no longer taking charge due to me accidentally using ...
1
vote
1answer
87 views

Help to identify resistor to remove [closed]

I just bought a solar powered LED light that has a motion sensor and a light sensor. When it is dark, it turns on but very dim. When it detects motion, it turns on full power (not very much...) for 20 ...
0
votes
1answer
89 views

Can I ignore resistor for IR LED?

I have two IR diodes and I want to connect them to my Raspberry Pi. From Pi I have 3.3V voltage. Diodes are TSAL 6200 . Can I connect them to PNP and my PI without resistor safely with this wiring?
-3
votes
0answers
46 views

resistor waveform

I tried to use a system to do the VI test accross the resistor in order to know whether it is good/bad resistor. Thus, I probe the resistor on both side of it in different frequency ranges which can ...
0
votes
2answers
65 views

Multiple resistors to reach needed value?

Im converting an old floodlight to a cree led to run off my solar setup for a yard light I need a 27ohm resistor for a 3.5v 350ma single led to run off 12.5v, but don't have any that value, what ...
3
votes
4answers
120 views

Which is the objective of an Base-emitter resistor?

Can someone explain me the purpose of the resistor R2? If I remove R2, the circuit will perform the same result, won't it? simulate this circuit – Schematic created using CircuitLab
9
votes
5answers
655 views

What is the difference between high precision resistors and current sense resistors

Actually, I am trying to build a current monitor for a wireless sensor network. I am going to use a current sense resistor as the current will pass through the resistor. By measuring the value of the ...
-2
votes
0answers
79 views

base resistor value

simulate this circuit – Schematic created using CircuitLab I am a beginner. I want to build this inverter for my academic project. I would be obliged if I could get some help. I am ...
-3
votes
1answer
96 views

What is the use of the 0.1Ohm Sense Resistor in Battery Charger

In the below circuit, can someone please point out the use of the 100m Ohm resistor? Can i replace it with a 0Ohm Resistor?
1
vote
2answers
70 views

Mosfet H-Bridge Design Question

I have a few questions regarding an H-Bridge design that I like. I am having a little hard time understanding some parts of it. So this is the design that I found online here. I changed the motor ...
0
votes
1answer
32 views

Essential Nodes in a Circuit

My book says above that there are three essential nodes in the circuit above. I am seeing four essential nodes in total which are marked by those four black dots. Since each of those black dots ...
-4
votes
0answers
60 views

calculation of base resistor for 2N6338? [on hold]

I am making a 220v 200watt 50Hz invertor with supply of 12v DC from battery.I didnt find BDY29 transistors with base resistor 33ohm 5watt in my locality.So I decided to use 2N6338 transistor.What ...
3
votes
2answers
65 views

Reducing 12 volts DC in a vehicle to 10.9 DC

I have a vehicle (12 volts DC) that has dash display that is too bright. If I install a potentiometer I can alter the power to get the display where I want it to be. This is 10.9 volts. If I read the ...
2
votes
1answer
68 views

Amperage limit of lead pencil resistor

What is a safe amperage limit for a homemade lead pencil resistor? I made a 25 ohm resistor with a regular wood pencil and would like to know what current it will take without getting hot to the ...
0
votes
1answer
36 views

Discharge / Bleeder resistors

I need to size and build a bleeder resistor network or could be as simple as two bleed resistors....im not sure but I have an application where a we have a step up transformer from 120VAC single phase ...
0
votes
0answers
47 views

Simple DC ramp up circuit

I am after a simple circuit that ramps from 0 to VCC relatively linear over a few seconds and ramps down only when power is removed for around the same time. I have been advised an RC circuit may be ...
1
vote
1answer
44 views

How do you calculate the resistor value for a bicolor led

R4 and R5 have equal values. For both LEDs the forward voltage is 2V and the forward current is 30mA. I know how to calculate the correct resistor for a single LED. However in this case I am using a ...
0
votes
1answer
59 views

Couldn't get a 741 OPAMP to work as inverting amplifier with smaller (but not so small) resistors

Using a 741 opamp, I constructed a simple inverting amplifier circuit as in https://en.wikipedia.org/wiki/Operational_amplifier#/media/File:Op-Amp_Inverting_Amplifier.svg ; I first tried Rf = 1k ...
0
votes
1answer
42 views

Constant Current IC Driving a String of ICs

I have been having difficulty wrapping my head around the ideas of constant current and constant voltage. Basically I have assembled this circuit with an arduino. Now, imagine that I wanted to ...
5
votes
6answers
814 views

What is the cause of voltage drop across a resistor? [duplicate]

We always assign a voltage drop to a resistor when a current goes through it in a closed circuit. I was wondering if this voltage drop is due to dissipated heat from the resistor or is there another ...
0
votes
1answer
59 views

Do force-sensing resistors draw current?

I know that a resistor in a series and parallel circuit would draw a certain amount of current. However, would a force sensing resistor wired with a 10k pull-up like in a typical microcontroller ...
0
votes
1answer
26 views

Find the thevenin equivalent resistance for the given circuit

I need to find the equivalent thevenin resistance, everything from the points A,B is exchanged.. however after I construct the image: It says the answer is Rth = 100 Ohm, but I can't figure out ...
-1
votes
5answers
122 views

Why does a resistor reduce voltage if V=IR? [duplicate]

I'm sure this is a very simple question, but I have been confused about this topic for a while now. According to Ohm's law, resistance varies directly with voltage. This means that if resistance ...
3
votes
1answer
37 views

Capacitors in parallel

I am using a old disposable camera to charge and discharge my Cap. I got 4 Caps and Connected them in Parallel (Hots to hots as is Grounds to Grounds). Can I use this just like normal? Can I just hook ...
-2
votes
4answers
66 views

Is it necessary to use resistor when connecting backlight of 16x2 LCD display?

I wonder if it's necessary to use any resistor when you're connecting backlight of 16x2 LCD module? OR it depends on voltage? I am using Hitachi HD47780
1
vote
1answer
241 views

Detecting When a USB Device Is Plugged In For Status LED

I've seen this asked a few times, but no definitive answers. I've also been Googling this for a couple days now with no definitive solutions. So time to ask... I'm building a fast charge USB charging ...
0
votes
3answers
75 views

voltage divider two unknown resistors

The circuit is made of a variable resistor of 10kΩ value and two fixed resistors R1 and R2 .The output voltage V0 should be variable from 2V to 9V, i have to calculate the values of the two fixed ...
0
votes
1answer
50 views

How small should I make my shunt resistor?

I have a small multi-junction solar cell that I will be taking measurements of short-circuit current and open-circuit voltage periodically in order to approximate an IV curve for the cell. I have ...
4
votes
2answers
198 views

The benefit to make or use a surface mount 4-terminal current sensing resistor

I find some precision SMD resistors are 4-terminal, like vishay's CSM3637P. It's constructed as below: It seems it only make a slot on each pad, then get two extra pad to do the voltage ...
1
vote
1answer
84 views

Can anyone indetify this SMD component?

This is from N9005 phone and i would love to know what SMD component is this. Here is a photo. Thank]1
1
vote
1answer
49 views

Power rating for opto-triac trigger circuit resistors

RHS will be using 220v 400watt bulb 2 simple questions 1- does the 360ohm resistors has to be of high watt too ? 2- all i can find is 5-10watt resistors, can i use them ? would they snub correctly ...
0
votes
1answer
53 views

Why this current sensing resistor called “Wirewound”?

I'm finding a current sensing resistor recently. I find Vishay's SR series, in it's datasheet, it tilted "Wirewound Resistor...". Is this type of current shunt really a wirewound type, but not a solid ...
1
vote
3answers
46 views

Current split between resistor and capacitor in parallel

I'm interested in knowing the formula which represents the voltage across the 10 ohm resistor. I know that it's going to be the current multiplied by the resistance, which means I have to find the ...
0
votes
0answers
48 views

Is a resistor necessary if supply and LED forward voltage is equal? [duplicate]

I have a 3,5V source and LEDs running on 3,0-3,6V. Is a resistor still necessary? Using an online "led resistance calculator" tells me I will need a 1ohm resistor no matter the current.
21
votes
5answers
2k views

Resistor Mounted On Top of IC?

Recently, I've been working to repair a broken 1980 "Arp Solus" synthesizer that I acquired from a friend. I have, however, found myself confronted by an unfamiliar arrangement: some kind of resistor ...
0
votes
2answers
57 views

Choice of current sensing reisistor

I need measure a 10A AC current, and need a 50mOhm current sensing resistor with tolerance <= 1% and good temperature stability. I find there are some choices, such as Vishay's RH,NH series, or ...
2
votes
1answer
45 views

Power dissipation when connecting LED to +-15v

In my audio project that is powered off dual +/-15v rails, I would like to connect a simple LED indicating power on. However, when I connect it with a 1.5k resistor in series (2W), the ~28V dissipated ...
-1
votes
1answer
112 views

Pull Up/Pull Down Resistor Confusion

I have googled the crap out of this but I can never find a good answer. In a circuit with a pull up resistor, why is the input pin fed current with a resistor? A pull down resistor circuit doesn't do ...