All Questions
Tagged with resistors circuit-design
121 questions
3
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2
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71
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Polarize and monitor a large resistor like device
goal
My goal is to design a board monitoring the resistance of a device which is basically a resistor (5-500 MΩ) in parallel with a capacitor (10-100 pF).
The device must be polarized (ie. the board I'...
- 33
-1
votes
1
answer
53
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Using constant current driver and/or resistor for LED
I want to mount some high powered XHP LEDs to a PCB in parallel. If I'm using constant current drivers that are separate from the PCB to drive current into it at the rated voltage of the LEDs, would ...
- 47
3
votes
4
answers
575
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What is the purpose of these 33-ohm series resistors on the RMII side of the LAN8742A?
Currently in the process of trying to figure out how to use this chip (LAN8742A-CZ-TR) in my own design and I'm looking at a few schematics using the chip as a reference. Both schematics make use of ...
- 35
0
votes
1
answer
60
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Using 48V 25A AC/DC power supply to power multiple components?
I was basically wondering if I may be able to control a NEMA 34 stepper (6.2A rated), Arduino Mega, and a linear actuator with just this single power supply (48V, 25A)? The NEMA 34 stepper would max ...
0
votes
2
answers
164
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RC circuit equation why have negative sign
I'm reading a book named The Art of Electronics.
What are some of the features of circuits with capacitors? To answer this question, let’s begin with the simple RC circuit (Figure 1.31). Application ...
- 297
0
votes
2
answers
80
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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 ...
- 293
2
votes
3
answers
170
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LEDs forward voltage at minimum brightness
I have a design issue. My circuit connects its MCU 5 V supply to two of these green LEDs in series with a 170 Ω current limiting resistor. I'm stuck with using two of the LEDs in series. I don't need ...
- 347
0
votes
2
answers
368
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Designing a current sensing op-amp circuit for an AC load
I'm trying to simulate a current sensing op-amp circuit. My AC voltage, 24 VAC, is across a load of 10 Ω. I used a 100 μΩ resistor and measured the voltage across it using an op-amp.
Looking at some ...
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0
votes
2
answers
107
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What is it about LEDs and resistors that makes it so order doesn't matter? [duplicate]
For reference: I was trying to figure out why I can put a resistor before or after an LED for it to work. I found an answer here that says:
The LED only sees the difference in voltage between its two ...
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1
vote
0
answers
37
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Seeking Advice on Resistor Package Selection for Voltage Sensing in BLDC Motor Controller
In a BLDC motor controller's voltage sensing circuit, I've seen larger resistors (1206/0805) used at the battery's positive terminal. I'm considering a 0402 package resistor for this spot. Are there ...
2
votes
2
answers
101
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Pull up or pull down resistor for potentially unused inverter input?
I'm using this TI Inverter that mandates that the unused inputs never float.
Sometimes, the inputs will NOT be used, and other times, all 6 will be used.
As such, it seems like I should use a pull up/...
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0
votes
1
answer
363
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Getting four times the power by arranging four resistors
If I'm given four resistors of value R and power rating P (each resistor dissipates up to P), what are ways I can arrange these resistors so that my circuit has a power of 4P and resistance of R?
One ...
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0
votes
1
answer
339
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RC circuit for EDM machine pulsing backwards
I am building a hackaday EDM machine project. Same as picture attached minus the 3D printer board and with a 120 V, 9 Ω setup instead.
I measured my voltages with a multimeter and across my electrodes ...
3
votes
3
answers
2k
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What is the difference between 1206 and 0612 (reversed) SMD resistors?
I wanted to know what is the difference and if a 1206 resistor can be chosen as second source of a 0612 if the other specifications are the same
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2
votes
4
answers
213
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Is there a systematic way to choose parallel resistors?
I'm designing a circuit, and I need a particular resistance. However, I don't have a resistor with that value. Therefore, I want to combine two resistors in parallel. In principle, with the parallel ...
- 181
1
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0
answers
124
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EPROMs /OE switching Circuit
For a personal project I'm trying to make a reproduction of a SNES game (Earthbound) which is 3mb in size.
Now the easiest way would be fitting the game in a 4mb 27C322 and multiplex the 16 bit bus to ...
- 111
0
votes
0
answers
320
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How can I download op-amp TL082 model?
I have just started using LTSpice. I need to simulate a Chua circuit with op amps TL082, but I did not find this operational amplifier. The reference paper which I have use that use this third party ...
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5
votes
2
answers
3k
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4 parallel LED's connected on a breadboard
I am trying to connect on a breadboard 4 red LED's in parallel (Forward voltage: 2V, max current 20mA). To do so, i followed the schematics below and used a 50 ohm resistor (put two 100 ohm resistors ...
- 179
0
votes
2
answers
103
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Computing the value of the passive elements in operational amplifiers
In the following circuit R1 = 30 kΩ.
Compute the value of the other passive elements so that:
The gain, when active is -3
The angular point is in +3 V*
R2 = ? kΩ
Find the value for Vr = ? V
R3 = ? ...
- 23
19
votes
8
answers
4k
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Why are kiloohm resistors more used in op-amp circuits?
In operational amplifiers working in the negative feedback configuration, the voltage gain depends on the "ratio" of resistances. In most textbooks I have seen that both feedback and input ...
- 397
0
votes
1
answer
57
views
Circuit understanding help
I am working on analyzing the following circuit. Could someone explain why there is such a big drop of voltage, from 4.24 KV to 0.707 KV? I am trying to figure out why the current is higher through Rf ...
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0
votes
1
answer
73
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Relation between sources and branch current
Assume a network consisting of N number of resistors, dependent current sources and voltage sources also independent current sources and voltage sources (ideal). Now the current across one particular ...
- 95
2
votes
2
answers
728
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Power delivered by this dependent voltage source
How can I approach this type of problem? Which different methods can be used here? KVL, supernode, mesh-analysis, source transform.
I tried using KCL on a node assuming its voltage V1:
...
- 95
4
votes
3
answers
2k
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Using resistor to drop voltage in circuit with changing current [duplicate]
I have no problem calculating and understanding how to drop voltage using resistor for circuits with purely resistive loads - for example look at much current will an LED draw, subtract source and LED ...
- 221
0
votes
2
answers
91
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Building a DC circuit that produces output voltage from 1 to 10 in 1V increments [closed]
I have been trying to design a DC circuit that can produce a range of output voltage from 1 to 10 in 1 voltage increments with just (non-inverting) operational amplifiers, switches, resistors, and ...
user335419
1
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2
answers
1k
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Why do we place a series resistor in the MISO signal of an SPI interface? What is the purpose of the and exact functionality of the series resistor?
I am working on a project in which I have to connect a 50R resistor in series in with the MISO signal line of a SPI interface.
My searches tell me it is used to match the impedance as well as ...
- 647
0
votes
1
answer
197
views
Fourth-order passive filter not behaving as intended
I have been designing a passive 4th-order RC low-pass filter in LTspice and was surprised to see that the slope is off substantially from what I would expect for a 4th-order passive filter. Instead of ...
0
votes
1
answer
54
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What's the most efficient way to add a heating effect to a smartwatch prototype?
Let's say I wanted to add the ability to warm up my wrist to a smart wristband. What component could I add to the wristband that would achieve that? Do I need to add a resistor?
0
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2
answers
565
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PNP transistor high-side load switching [duplicate]
I want to use a PNP transistor to switch off a load. I have a microcontroller that can give an output of 3.3V on the base of the transitor. The load can opparate at 3.3V also.
The idea is when the ...
1
vote
1
answer
287
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What is a suitable resistor value for this circuit?
See the small circuit of a PIR motion sensor below. I've tried to find more than one circuit online but every single time it shows a different value for the resistor.
I would be grateful if anyone can ...
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0
votes
0
answers
100
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Electronics Lab - Not measuring voltage drop across resistor connected in series with capacitor
I'm working on an RC circuits lab for school, and it stated to connect a circuit as follows: 15VAC in series with a 470-ohm resistor and 4.7uF capacitor and measure the voltage drop across the ...
8
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4
answers
829
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How to find resistors from E series for a certain ratio?
Given is a ratio for resistors, e.g. two resistors \$\frac{R_1}{R_2}\$ = "some odd value", like 257:42.
How do I find matching resistor pairs (triples, ...) from E series, without having to ...
- 183
2
votes
4
answers
439
views
Battery with resistor: looking for verification that my understanding is correct
If I have a 12 V, 18 Ah battery, and I use a 4 Ω resistor, I will have 12 V and 3 A on the other side of the resistor, and I will have a current for about 6 hours - correct?
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2
votes
0
answers
514
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How to choose component values for a JFET common-source amplifier?
I am trying to design a simple common source jfet amplifier using a J109 transistor.
I'm using the J109 datasheet and equations from the book Electronic Devices by Thomas L. Floyd.
The issue is that I ...
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-3
votes
2
answers
560
views
What value of resistor is needed to limit current to 0.5 ampere in a 12V DC circuit?
I have a 12V DC motor that uses 1 ampere from a 12V battery. I want to limit it to 0.5 ampere because it runs too fast on 1 ampere. I know that I can achieve that by adding a resistor but the question ...
1
vote
3
answers
436
views
Nichrome strip and resistor
I'm trying to build a heater connected to 220 VAC, 50 Hz using a nichrome strip (2.3 Ω/m) and I'm going to use 1 meter or less (60 to 70 cm).
I know that this setup won't work at all with 220 VAC so ...
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0
votes
1
answer
189
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Do I need a current limiting resistor with an industrial rail DIN optocoupler?
I'm going to use this industrial opto-coupler:
Optocoupleur RS PRO, montage Rail DIN, 6 mA
In its specs document they don't mention the need of a current limiting resistor. I always add a current ...
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0
votes
0
answers
375
views
Activate arc lighter with Arduino
I have a SaberLight plasma arc lighter, and I have taken it apart for a flamethrower project. I would like to use an Arduino Uno to programmatically activate the arc lighter. Using the Arduino Uno, ...
0
votes
2
answers
204
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Using resistor with 110 V LED indicator to make current measurement between 50 - 70 mA
I need your guidance with the V=IR formula. It's probably a simple question but I don't have an electrical background.
I am working on making an LED simulator panel for railway signaling interlocking ...
- 3
0
votes
4
answers
233
views
Resistance averaging circuit / resistance divider circuit (NOT voltage divider)
I'm trying to design a circuit to average 3 Pt100 resistors to feed into a single temperature controller.
All the solutions I've found so far involve either a microcontroller or a complex opamp + ...
- 1,374
0
votes
2
answers
306
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Why I am I unable to turn on a load when Wheatstone bridge is connected in series with the load
I am trying to switch on a load by using a Wheatstone bridge and planning to provide the differential voltage to the transistor.
Before doing that, I am trying to use two batteries (second one ...
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0
votes
4
answers
2k
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Can I use this simple debounce RC circuit for Arduino?
The values for the resistor and capacitor are what I will be using. This is the circuit I will be doing because using two resistors might take up too much space. I will be replicating this circuit for ...
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0
votes
1
answer
210
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Voltage issue on pull-up resistor
I have an I2C sensor circuit, 3.3V applied to SDA and SCL pin through 10k resistor.
I2C communication is not working so I have measured the voltage drop across the 10k resistors. It drops 2.86V and ...
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-2
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1
answer
74
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What is the difference between making a resistor based keypad and not using a resistor on arduino? [closed]
I've seen videos on youtube about how to emulate a keypad on arduino. Some of them includes a resistor while others do not. What are the difference between them and are there advantages in doing one ...
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3
votes
2
answers
841
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Math behind pull-up resistors
I have a question about the the math behind of pull-up resistors and how they work. I don't have any experience in the Electric Engineering field so it's probably a basic question.
I saw many ...
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0
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1
answer
96
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Power calculation of this circuit
Can someone tell me how to approach this question. I am not sure on how to calculate it. I tried to simulate it. But got this
How to understand this and calculate the power in the circuit?
user220456
1
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5
answers
3k
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RC peak detector calculation
Before the edit was made
I have a signal that is an AC signal and I would like to track its envelope. I'm not doing AM, I'm trying to make a transducer for my sensor. Frequency is constant but ...
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2
votes
1
answer
1k
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Why does the position of the resistor matter here? (Arduino)
I made a small circuit that when someone push a button a servo rotates to 90° and go back to his initial position after a certain amount of time.
My issue was with the resistor. I needed it to be in a ...
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2
votes
4
answers
7k
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RC circuit resistor power dissipation
How do you calculate the actual power dissipation across the resistor in an RC circuit?
For instance, 12 V source, 10 Ohm resistor in series with 100 uF capacitor, no other load connected.
12/10 = 1....
- 301
4
votes
2
answers
3k
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What does a resistor value of NP mean on a schematic?
I'm trying to design a schematic based off a certain schematic I've seen online. In the image theres two resistors and a capacitor all with a value of 'NP'. What does this mean? I'm guessing it means ...
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