Questions tagged [basic]
Fundamentals of electricity, electronics, components, or theory
591 questions
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Simple current source with bjt
I want to learn how to design a simple current source using a BJT.
I found this picture on another site (https://www.wellpcb.com/blog/pcb-projects/constant-current-source/?utm_source=chatgpt.com), but ...
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4
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2
answers
256
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How will current flow in this 120 Vdc circuit when various switches are closed? (homework)
Answer to 2 is D and to 4 is B. I'm having trouble understanding the logic behind these answers.
For Q2: How will closing switch #4 prevent lamp from lighting up? Wont current just flow through both ...
4
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4
answers
129
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Difference between the two ways to state KVL
I am reading LINEAR CIRCUIT ANALYSIS by DeCarlo and Lin.
The books states KVL in two ways. I wanted to ask if the second way offers extra functionality or simplifies some abstractions. Or it is just ...
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2
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163
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Is there really any safety concern (beyond the obvious), regarding putting 240vac mains into a basic potential divider that is 210k Ohms?
I have been perplexed recently with regards to people on a forum, stating that it is unsafe to put 240vac directly into a basic potential divider. The divider was literally 210k ohms, with 3 resistors....
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1
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Looking for some very basic, or maybe advanced details of how to wire and configure a 12vdc horn siren
I have purchased a 12vdc horn siren:
https://www.amazon.co.uk/dp/B0CHM41B54?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1
(I hope that does not get flagged as spam! If it does then I do not really know ...
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1
answer
52
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Squeezy bottle battery equivalency question [closed]
If a squeezy bottle of water is high-volume and lower-pressure is the equivalent of that in electricity high-amps and low-volts?
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2
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134
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Path of current in a DC circuit
This is more a basic circuit question than specific to transistors. So if a high enough voltage is supplied to the base of the transistor, the path between the collector and emitter is open. Thus ...
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2
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188
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Constant current with sine pulse [closed]
I'm trying to make constant current with a sine pulse as an assignment from my project supervisor, the problem is I really can't imagine what a constant current that has a sine pulse at all, it just ...
2
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2
answers
167
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Conducting anti-series diodes in LTspice
Consider this simple LTspice simulation: two diodes in anti-series, supplied by a 20 V 10 Hz sine generator with a 1 kΩ series resistor. I expected the K node voltage to be always about 0 V. Instead, ...
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8
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Putting an Ammeter in Parallel with a Wire but Still Having Series-Resistors
I am currently studying EE and am still very early on in my studies. In one of my principles class, my professors showed us the following circuit:
simulate this circuit – Schematic created using ...
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4
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212
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Electric potential in an open circuit
I've been learning Electronics from scratch and have a few misconceptions. I don't understand why in this circuit point B is at the same potential as point A. It stands to reason that there is no ...
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3
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140
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How can the equivalent resistance of this RLC tank circuit be 18 Ω?
I was trying to resolve the following problem:
A 6.8 kΩ resistor, a 7 mH coil, and a 0.02 uF capacitor are in
parallel across a 17 kHz ac source. The coil's internal resistance,
RW, is 30 Ω.
The ...
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4
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4
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742
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Help me understand BJTs better. Resistance of Base Emitter on BJT
From my understanding, bjts will have a diode from the emitter to the base. I was measuring the resistance of a BJT and found that the resistance between the emitter and base was about 500kohms when ...
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1
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I2C SSD1306: single vs double transaction
Based on answers to my previous post - I have a question about basic I2C transactions.
If a basic transaction has the following structure:
start
chip address
bytes to chip
stop
I am wondering if ...
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3
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795
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Op-amp voltage follower basic understanding
First of all following experiment with a simulation:
I have a basic question to the voltage follower. Normally a voltage follower is constructed the way of the top circuit in the image. And this ...
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1
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167
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Transistor Testing Circuit
In my previous posts I started way above my knowledge level so I decided to go to the basics. I googled online and came across this transistor testing circuit. I was hoping someone could tell me if I'...
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2
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How to convert current directly to frequency in the simple 555 frequency meter
So I'm working on an audio project, and I need a built-in frequency meter (for tuning the instrument, basically, so the range is like 50 Hz - 5000 Hz with an required accuracy around 1 Hz). I see a ...
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8
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2k
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Circuit that turns two LEDs off/on depending on switch
I have been trying to solve this for the last couple of days and no matter what I do, green LED always receives some current.
What I would like to happen is when the switch is closed, turn on just the ...
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6
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276
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Do components "draw" current, or is it forced through them? [duplicate]
If you attach a typical LED to a 9V battery, the LED will burn out because there's too much current. If you add a resistor, it's fine.
You can charge your phone with a 1.0A charger, a 2.4A charger, ...
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Can you help me understand W=I*V - house load
So I'm trying to work out my daily Ah usage for an off-grid set up (and to see what my power bill at this new place might be like).
Context:
I've gone through and created a sheet with the appliances I ...
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0
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104
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Control Glade Device with AtTiny85
I am a programmer, without knowledge of electronics and I want to be able to make a control that allows:
intervene the power supply in a Glade aromatizing device, so that it is activated only during ...
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0
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328
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How do I use ideal MOSFET model in LTspice? or How do I set voltage in node without voltage source?
I want to simulate the principle of 1T1C DRAM cell. But if I model voltage source in Bit line, bit-line voltage is set by its input signal. So I want to seperate bit line, using ideal MOSFET component,...
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4
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6
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2k
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How is he not shocked? [closed]
I'm new to electronics, and I can't make sense of this video. At the 9:10 second mark, he holds a metal spoon across the ends of a wire that's carrying around 100 amps, and he's not harmed. Later the ...
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2
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529
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Confused about usage of Ohm's law & Kirchhoff's laws to solve a circuit
I'm solving this circuit using Ohm's law and Kirchhoff's laws:
I solved the circuit correctly the second time.
Equation A:
$$I_1-I_0-6=0$$
Equation B:
$$-120\ \mathrm{V}+I_0\cdot 10+I_1\cdot 50 = 0$$
...
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2
answers
91
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Understanding reference levels in circuits
I understand that a zener diode uses its anode as a reference to limit the over-voltage levels that appear on its cathode. However, in the circuit shown below, I am confused about why the anode of the ...
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2
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2k
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LED Fails to illuminate, what am I not seeing in my configuration(s)?
I'm working on a super simple circuit, I want to light the LED.
Power Source 1: 5.5v from 9v battery through breadboard power supply module
Power Source 2: 5.5v from lab bench PSU
LED Info: Vf - 3v to ...
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0
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2
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161
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Asymmetric LC tank with diodes
Is there a circuit that can produce an asymmetric wave, where some parameters of positive and negative half waves are different, such as voltage amplitude or time?
Intuition says that we need a ...
5
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7
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Why did current increase when voltage decreased?
I was taking a short course on home electronics (mostly just how to safely change sockets, switches, and bulbs) and the instructor told an anecdote about how when the energy company accidentally ...
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3
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488
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Can you explain why doesn't current always go through the first part of a parallel circuit (without water or heavy math)? [closed]
I have tried to understand this over and over. I don't understand how current ever makes it beyond one branch of a parallel circuit. I apologize for the circuit if it doesn't make sense.
I simply do ...
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8
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2k
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How does electricity transfer energy?
I am new to electronics and was just looking for some intuition behind how electrons give energy to components.
I have been attempting to understand this under the condition of voltage being the ...
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2
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161
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Connected negative contacts of 2 supplies [duplicate]
When the negative contacts of 2 power supplies are connected with a wire they share the same base potential that can be associated as GND.
But why does this happen? For me it's a bit magical that the ...
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0
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82
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Mix of power supplies
I am struggling to understand what happens when two power supplies are connected:
Both supplies build a whole circuit, the rest of the second supply is left out for simplification
Both power supplies ...
- 149
1
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2
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199
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Voltage distribution with two batteries [closed]
I have a question regarding a simple circuit of two batteries (9V) in series with a single resistor connected to the outer contacts to prevent a short.
When I'm simulating this circuit, a current also ...
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0
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2
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249
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Is passive sign convention the exact oposite of active sign convention?
I'm currently studying the fundamentals of electrical circuits. For my studies, I'm using the book "Fundamentals of Electric Circuits 5th ed."
In the introduction chapter, section 1.5 Power ...
0
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2
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390
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Which is the correct flow of current in these following circuits for nodal analysis?
My professor told me one method, a well known and trusted youtuber told another method and our assignment solutions have another method for nodal analysis so I can't figure out which method is ...
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2
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267
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Step response v/s DC voltage
I have to find step response for this circuit considering my input as Vo and step for Vin( I am using Simulink for this)
Firstly what i did was making this circuit (DC voltage is 1V)
The response on ...
2
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3
answers
359
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Thevenin/voltage logic
So, I'm trying to find the Thévenin voltage of this circuit. I understand that the resistors (R+3R) by node a are irrelevant as there's no current running and thus no voltage drop. However, I'm a bit ...
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1
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399
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Confirming behavior of a diode in an open "circuit"
I have built the "circuit" illustrated below. Basically its a 5V supply with positive terminal connected to a schottky diode's cathode, multimeter in voltage measurement mode across the same ...
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1
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179
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Why is this oscilating circuit not possible [closed]
In my mind, this circuit should oscillate because the transistor draws the entire power when turned on. This, in turn, should cause the base to turn off, opening it back up and continuing the cycle. I ...
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1
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1
answer
108
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Can a transistor replace a switch that closes ground to an input?
I've been browsing on Google for quite a bit now but couldn't find an answer.
I have a remote that triggers the shutter of a digital camera.
According to the schematics that I've found, the ...
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1
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How to set current on a cvcc?
I got a cheapo cvcc off ebay.
Setting volts is pretty easy. I just hook my multimeter leads to the output and twist.
But, how do I set amps? I need something to dump the current in. What should I dump ...
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Questions about a CTAT circuit
Please refer to the following CTAT circuit
source: https://wiki.analog.com/university/courses/electronics/text/chapter-14
The following notations are used:
VR1 - voltage across resistor R1
VR2 - ...
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1
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174
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An active inductor connected to an inactive inductor in series
I am a grade 12th student studying about inductors and RLC circuits for the first time. While studying I got stuck with the idea of an active inductor being connected to an inactive inductor.
...
0
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4
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216
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How to read circuit diagram [closed]
This is a basic question but I am a little bit confused on how to interpret this diagram. What are the symbols that are present in this diagram? What happens when there is current running through the ...
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2
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121
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An old 9 V inverter circuit
I wanted to discuss and ask questions about an old inverter circuit I built 15 years ago when I was studying; the circuit was powered with an ordinary 9 V battery-Duracell type, and steps the AC ...
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0
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76
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Help On Dual Amplifier Design
I am pretty new to electronics and so far, have been teaching myself and designing things with the help of the internet. I made and designed a class-AB amplifier circuit that drives two 8-ohm speakers ...
0
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1
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141
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Choose the RLoad resistor for zener diode
I need to calculate the Rload resistor range for the operation in this case:
I know that many times to calculate the Rseries but now he is given,
how does my teacher expect me to calculate the RL?
...
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2
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708
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Where does the current applied to the gate of a transistor "go"?
In the following circuit, the LED lights up:
I was afraid I'd misuse the transistor symbols, so I just drew a box to make sure I communicated the right thing. This is the transistor, G/D/S means Gate/...
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2
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Why is my transistor is letting through current?
I'm working my way through the Arduino starter kit project book and am doing the first project involving a transistor (MOSFET). As far as I understand, what I've done is wired up a 9V battery, a ...
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2
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Understanding how the input pins on my Arduino Uno read voltage
I recently bought an Arduino starter kit which comes with an Arduino Uno and some components. I know very little about electronics or physics. The Arduino has some analog-to-digital pins on it which ...
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