Questions tagged [basic]
Fundamentals of electricity, electronics, components, or theory
443
questions
5
votes
4answers
824 views
How do I determine whether a switch can handle the power/current in a circuit?
I have a switch that has "3A 250VAC" and "5A 125VAC" printed on it, which I imagine are ratings of what the switch can handle, but my understanding that 3A at 250V would be 750W ...
0
votes
2answers
45 views
Basic Series/Parallel connection understanding
I am just starting out with electronics and I have understood that there is something fundemental I just cant seem to figure out about parallel and series connections. I am having a lot of trouble ...
3
votes
1answer
91 views
Is it safe to cut these wires?
My kid got a face mask with flashing eyes, but there's also some annoying sounds that comes with it. Is it totally safe to cut the white wires or could the awesome flashing lights stop working too (...
1
vote
1answer
110 views
Circuit with 1 diode in parallel with a resistor
Sorry if this question has been answered here before, but I just can't seem to find any info on this.
A little background. I am currently doing an automotive mechatronics course and, while I know some ...
0
votes
5answers
210 views
Basic BJT current mirror : … so the collector-base voltage of Q2 is also zero?
From this schema
I don't understand this sentence from here, particulary in section "Basic BJT current mirror"
"...If Q1 and Q2 are matched, that is, have substantially the same device ...
2
votes
2answers
69 views
Please help me with finding if I need to add a resistor to my circuit
I want to connect 3 4V LED strips in series to a 12V, 1A supply. Each strip requires 250mA current to operate. This makes a total of 750mA required current for all 3 strips. My concern is how should I ...
0
votes
1answer
59 views
Resistor across output?
I'm trying to learn about gates.Why is a resistor connected parallel across the output?
0
votes
2answers
64 views
RC Low Pass filter, capacitor in series or in parallel?
I've seen 2 variations of the RC low pass filter, sometimes with both the resistor and capacitor in series, and more commonly with the capacitor going straight to ground. What is the difference ...
0
votes
2answers
161 views
2
votes
3answers
218 views
Why does the voltage drop across an LED matter when determining an appropriate resistor value?
In determining the voltage dropping resistor, why is the forward voltage of an LED deducted from the supply voltage instead of considering the supply voltage alone?
1
vote
1answer
119 views
Wiring RGB Strip LEDs w/ just positive and negative wire [closed]
I'm working on a small project, and I had some leftover strip LEDs lying around. They're just the RGB strip LEDs you can pick up at Five Below. They come with an RGB controller attached to a short USB ...
0
votes
1answer
53 views
steady state voltage in capacitor network
simulate this circuit – Schematic created using CircuitLab
I have this capacitance network in my circuit and I can't figure out the math behind why the final steady-state value of Vx=0.542v when ...
0
votes
2answers
45 views
Resonant frequency and maximum signal width
I've seen resonant frequency being defined as the point where the input signal is in phase with the output signal (So reactance/susceptance is 0).
However conceptually, teaching material seems to link ...
1
vote
0answers
85 views
Audio amplifier circuit explanation
Recently, I am working with amplifier circuits but circuits available online for an op-amp have some extra components with respect to what we learn in textbooks.
I know the basic amplifier components ...
3
votes
0answers
34 views
Current Divider with dependent source
I'm currently studying electronics for the first time. The objetive of this exercise is to calculate the current I and the dissipated power in the dependent source. However, I'm having a hard time ...
0
votes
1answer
31 views
Trigger two circuits with single SPST switch
I'm an electronics noob willing to learn. So I have a door bell that looks like it is wired like this:
And I've bought a fancy 3V battery powered device that is intended to be wired simply like this:...
1
vote
2answers
63 views
Output characteristics of transistor
Why is the slope of output characteristics of transistor in CE configuration more than that of CB configuration??
0
votes
1answer
102 views
Find the Thevenin's equivalent of a circuit between nodes A and B
My class had come to discuss the Thevenin's theorem and we stumbled upon this particular problem which quite confuses me in a way that what I found is different than what my lecturer taught us. So, ...
2
votes
1answer
74 views
Power supply module on breadboard giving too much voltage
I'm currently following the tutorial "Electronics Fun Kit" by ELEGOO. The goal is to connect the power supply module with the breadboard in order to provide a 3.3V / 5 V source.
After connecting the ...
0
votes
1answer
42 views
(Basic) How to connect the ground in this schematic to a breadboard?
I just want to know how do I connect the ground in the circuit. I know how to connect DC source but I'm confused on how to connect the ground. I have adept knowledge about the concept of ground, I ...
1
vote
0answers
67 views
Testing a LM111P comparator
I have the LM111P voltage comparator (datasheet.)
I am learning my ropes with electronics, so I am moving thru the easiest topics to more complicated ones. If I understand correctly, when I provide ...
1
vote
0answers
43 views
Separation of channels in simple audio LED VU meter
I'm trying to build a very simple VU meter based on LEDs and transistors. I used this tutorial as a base - basically I copied the LED array setup but replaced the input with full bridge rectifier. My ...
3
votes
5answers
1k views
Why is it called Wired-OR when it is functioning as Wired-NOR?
Inputs: Base of bjts
Output: black node
When at least one of the inputs is HIGH the output is LOW.
This is clearly NOR. Then why everyone calls it Wired-OR?
2
votes
2answers
96 views
Op amp outside resistive network
Usually I don't care about algebra and just focus on the functionality. However, below circuit form appeared so many times in last few days in op amps that I thought of memorizing it by heart.
From ...
0
votes
3answers
140 views
Two charged capacitors connected in series
simulate this circuit – Schematic created using CircuitLab
The circuit has the initial condition as shown in figure. What will Vfinal be when SW3 and SW2 are open but SW1 is closed.
2
votes
2answers
59 views
How is it possible to force \$v(t)=\cos(t)\$ as voltage input to a fully discharged capacitor?
Let initial charge on capacitor \$Q=0\$ and say \$v(t)=\cos(t)\$ is applied for one period(\$2\pi\$ seconds) across the capacitor. Then the current will be \$i(t) = C\cos(t+\pi/2)\$. Clearly the ...
0
votes
3answers
75 views
In an equation like i(t) = CdV/dt, is “V” the cause and “i” the effect?
In mechanics, almost all the time, force is the cause and acceleration the effect. If you apply a net force on an object, an acceleration can be observed. However this seems not that straightforward ...
0
votes
2answers
41 views
How does difference in loads affect current draw
This is a side question to 487370/limit-charging-current-to-a-smartphone. Hopefully it will clear the confusion in my head.
Say we start at 5.5V with a series resistor of 1 ohm, that will leave 5V ...
0
votes
2answers
69 views
Transformers and wattmeters
This is, probably, a very silly question, but I was thinking:
If you have a watt meter and you connect a step up transformer with the lower voltage side attached attached to it (both the voltage and ...
0
votes
2answers
63 views
Thevenin's voltage
I'm trying to solve and exercise (see picture) where I'm supposed to find the voltage drop between 2 points in a circuit, using Thevenin theorem. I removed the resistance between those two points.
...
1
vote
4answers
76 views
How do I find the missing equation?
This is my first post here, hope you all doing well. I'm a CS student, having my first class on circuits. I've been given this problem (see picture) where I'm asked to find V2. I'm missing one ...
0
votes
3answers
138 views
How Does Kirchoff's Law Make Sense
I understand the algebra, and I can also use Kirchoff's Law in calculation.
But I struggle to understand how it makes sense logically.
The law states, that the sum of the currents entering a ...
0
votes
3answers
111 views
Why are LEDs so tolerant of voltage?
My electricity knowledge is about high-school level or so. Just about enough to be dangerous...
Back when I was a kid I used to play around with 4.5V DC power sources, buttons, switches, relays and ...
0
votes
5answers
141 views
Will a capacitor draw charge/current if it's not feeding a load?
I have a number of capacitors connected in parallel, as in the following circuit:
simulate this circuit – Schematic created using CircuitLab
If the switch is open, will the caps still draw ...
0
votes
0answers
66 views
8000 Amps across a 1 A diode for 0.2 uS
Assuming that the diode is rated for 20 kV and the pulse is only 250 V, will a 250 V 8 kA pulse that lasts 0.2 uS break a 20 kV 1 A diode? This also assumes that the diode recieves 10 of these pulses ...
9
votes
4answers
4k views
Do capacitors waste power as heat or whatever on AC?
Capacitors store energy then give it back once required. A perfect capacitor is nearly lossless on DC power because you only fill it once then it keeps energy in it until you discharge it so no power ...
0
votes
1answer
36 views
How to calculate voltage of these nodes
How exactly does one calculate the voltage of the marked nodes and arrive at the numbers in the picture (1.75 and 1.628)? I fail when trying. :(
simulate this circuit – Schematic created using ...
0
votes
1answer
33 views
Comparing transformer set ups
Is it practical to connect the output of a ferrite-core 1:40 transformer in series with the input of a 1:6 ferrite-core transformer as a means of acquiring 240 V?What would the pitfalls be of this ...
0
votes
0answers
74 views
How to prevent common ground circuits messing with each other
I made an Arduino based 18650 battery tester that has 4 identical circuits that charge and drain.
Testing one battery at a time gives one set of results which I deem to be correct but testing more ...
1
vote
2answers
168 views
Wiring a Potentiometer for a positive voltage
I am attempting to make my own adjustable voltage supply that provides a positive voltage (anywhere from 0 to +200 VDC).
The sections I have devised so far are able to provide 450 VDC, however I need ...
0
votes
4answers
92 views
Alternating voltages on vintage calculator circuit board
I am an electronics novice.
I have a vintage calculator with six secondary wires coming out of its transformer and ending on the board, as shown below:
Using the AC portion of the multimeter, I ...
0
votes
2answers
137 views
220 volt step-down transformer with 6 secondary wires
I am an electronics novice. :)
I opened a working Casio vintage desk calculator (likely from the late 1980s/early 1990s). It has a 220 volt step-down transformer with six secondary wires. The two ...
0
votes
1answer
49 views
Preservation of power when wiring batteries in series - battery life is reduced if load is kept the same
This is really just a "sanity check" type question. Am I correct that if you place two batteries in series, that the battery life is effectively halved relative to just one battery, assuming the load ...
14
votes
6answers
3k views
How does an SR Latch get started [duplicate]
Noob question, but I'm not seeing how an SR latch such as the one in the image can "get started". If each input depends on the output from the other, how can there be two inputs to each gate to set ...
1
vote
3answers
105 views
Help explain op-amp description by Forrest Mims
The following description is from the book Op-Amp IC Circuits by Forrest Mims (2nd edition 1994):
As a newbie, the entire paragraph is counter-intuitive to me. If amplitude is reduced, why is there ...
0
votes
3answers
43 views
Voltage Rating of Capacitor Set Up
A buddy of mine just told me that the set up (linked to the question on Circuit Lab) would be able to handle 500 volts DC, even though each capacitor is rated for 20 volts DC. It was to my ...
0
votes
1answer
80 views
PIR sensor bypass for LED light strip
I don't know that much about electronics, but I was able to put together this PIR module:
(original)
and a LED strip and everything works just fine, when the PIR detects motion, it turns the strip ...
0
votes
3answers
191 views
Electricity path through a 240V heating element
My simple understanding of electricity is that you always need a circuit (from + to -, or from hot to neutral), in order for current to flow.
Now, I recently had to fix my water heater (which is ...
0
votes
1answer
78 views
How can I make a simple circuit to output only after a min input voltage is exceeded?
Here's my problem....
I am setting up a camera system on a motor coach that is designed to trigger separate cameras when blinkers or backup is engaged.
the problem I'm having is the only accessible ...
0
votes
2answers
53 views
Explanation results of RC simulation wih LTspice/Micro-cap
I built a basic schema with resistor, capacitor, ground and a battery in LTspice and MicroCap.
I used transient analysis mode.
I expected to see on a chart decreasing current and increasing voltage ...
