Questions tagged [basic]
Fundamentals of electricity, electronics, components, or theory
0
votes
2answers
56 views
Why did Adafruit pick a 10K resistor for this phototransistor breakout?
Adafruit has an ALS-PT19 Analog Light Sensor Breakout. It looks like it has a 10K resistor on it:
The ALS-PT19 datasheet says that resistor is to convert the output current of the transistor to ...
0
votes
1answer
27 views
How do I determine the capacitor to use when converting current to voltage?
I'm trying to figure out how to use an ALS-PT19-315C/L177/TR8 phototransistor (or something like it).
The datasheet has this sample circuit for converting current to voltage so that I can measure it ...
1
vote
1answer
44 views
How do current and voltage relate to load?
I think I've lost the plot somewhat on how current and voltage relate to the load in a circuit and I'm hoping for some really basic level clarification. In fact, I'm not really sure how to ask the ...
0
votes
0answers
34 views
Why doesn't current leak to ground (DC)? [duplicate]
In the circuit shown below, I am considering ground to be ideal earth ground (stays at 0V no matter how much current it absorbs). It is my understanding that current flows when there is a potential ...
0
votes
3answers
79 views
Possible reasons for differences in voltage between garage opener circuit and Raspberry Pi
I am attempting to use my Raspberry Pi's GPIO to activate a garage door opener (specifically Craftsman 139.5364812). As far as I can tell, the garage door is operated by shorting two terminal screws ...
0
votes
5answers
98 views
A basic question about amps, watts, and charging batteries
Why do we speak of watts (and not amps) when we refer, for example, to the "7.5W Wireless Charger for iPhones," but when we talk about cord-based USB charging, the specs typically refer to amps (and ...
0
votes
0answers
48 views
This is a basic question but I'm confused please help [duplicate]
I need to power my circuit. I have a power supply of 12v 8.5 amp my circuit needs 12v 1 amp.
What do I need to do?
0
votes
1answer
45 views
monostable Eccles - Jordan multivibrator, theory
I’ve a few problems and questions to the principle of monostable multivibrator’s work. Basic schematic is as below:
What is the reason for D1, C1, R3 elements at input? Why I can’t just tie a ...
1
vote
1answer
94 views
What is the purpose of extra parallel resistor R2
This probably is a very basic question. I looked at a real world device schematic - a "digital pushbutton" and can't figure out why R2 is necessary.
This device is supposed to be connected to arduino....
0
votes
3answers
116 views
Confusion over the power wires of USB (GND and +5v)
I'm converting a battery powered device to be powered off a USB connection. I think I have everything figured out except one thing.
I understand there is a GND wire inside the USB cable for power, ...
11
votes
2answers
1k views
What role does this diode play?
I've just bought an Arduino Uno kit, and am going through all the projects in the booklet that comes with the kit. From even the simplest LED and resistor circuit, to get a feel for the Arduino board, ...
1
vote
2answers
62 views
Can't understand a given answer about a 1st Kirchhoff's law question
I am currently studying the textbook "Lectures about the fundamentals of Electrical Engineering" by Adalbert Prechtl and after finishing the theory about Kirchhoff's law, I tried to solve some basic ...
0
votes
2answers
90 views
741 Op. Amp.: Inverting input connected to output (pin 2 connected to pin 6). What does it mean?
simulate this circuit – Schematic created using CircuitLab
I am a newbie electronics students.
My question is, what does it mean (what happens) when you connect pin 2 to pin 6 on a 741 op. ...
0
votes
1answer
31 views
How can I solve for impedances if given RMS currents?
Given a very simple circuit such as this.
If I where given the RMS values for the three currents, how could I go about solving R and Xl? (the resistor and inductor in paralell)
I know I can not ...
0
votes
1answer
57 views
how to wire together multiple photoresistors to make one big sensor?
I'm using an esp32 dev board, and a bunch of 5v laser diode emitters pointed an equal number of photocell resistors across a plane. The goal is only to detect when any two or more beams break at the ...
0
votes
2answers
33 views
Bjt for trigger MOSFET
I my project MOSFET need 13 v 65% PWM to trigger but controller output is 5 volt then how can I amplify this in voltage
0
votes
2answers
53 views
Maximum output power of a PA
I was discussing with a friend about maximum output power of a (class A/B power) amplifier (for example if the device following the PA can only tolerate a certain amount of power).
If the input power ...
0
votes
2answers
31 views
Source transformation violation
Using thevenins or norton theorem, we can easily find current through the resistor as 1 amps.
But if we convert the current source to voltage source , current turns out to be zero amps . Why?
0
votes
2answers
51 views
I need help finding the equivalent resistance
Hello guys , i'm new in the amazing world of electronics , and im very confused with this circuit . Im supposed to find the Req (equivalent resistance , but dont know how in this specific circuit), ...
1
vote
1answer
96 views
Basic question about conduction current
Sorry for my english and long post again.
After reading this article, I realized that my understanding seemed to be wrong.
I thought that to create conduction current in some wire first we need a "...
-1
votes
1answer
197 views
why does a fuse break when a wire is connected to ac socket directly
I connected ends of wire to ac hot and neutral points of ac outlet sockets - an electric fuse broke and power went off in my house. I understand this happened since there was closed circuit ...
0
votes
1answer
99 views
RS485 to RS232 conversion?
I need to connect a sensor that uses a RS485 transmission to RS232 or something I can read through the com ports on my data logger. I can't use usb ports or virtual com ports due to the program I am ...
1
vote
2answers
103 views
How do you model a “leaky inductor”?
My understanding is as follows:
A voltage induces an electric field at a capacitor, which is measured in coulombs. If I wanted the capacitor to leak the charge exponentially, I could model that as a ...
3
votes
6answers
385 views
What's the rationale behind these warnings about extension cords?
(Disclaimer: I've read the help center and I do understand that this is bordering on off-topic since it's about consumer devices. However I hope that I've managed to make enough on-topic by asking ...
1
vote
2answers
186 views
A few basic questions about simple electric circuits
For beginning, sorry for my english and for long post. But maybe it would be useful for others newbies. I'm trying to understand basic things about electric circuits on my own, and at the moment I ...
0
votes
1answer
31 views
Calculating for Load Resistance given a T network in between the source and the load
Problem: Calculate the value of load resistance (Rl) for which maximum transfer occurs.
Attempt: What I know is that for the maximum transfer to occur, the load resistance must be equal to the source ...
8
votes
1answer
704 views
Understanding this circuit with op. amps
I'm studying electrical engineering and I've came to a problem, where I cannot proceed. It's a "simple" task, where we're talking about an inverting op.amp with 2 voltage sources, each 1V, while all ...
0
votes
2answers
28 views
Figuring out if an led strip/matrix has a short or not with a multimeter
I am relatively new to electrical work, mostly stay on the software side of things. I recently soldered header pins onto a few led matrixes I have. They are 3 wire leds (power, data, ground). I'm ...
2
votes
2answers
103 views
Basic question I would like to be solved
Can someone please solve this for me, telling me what's the right option and why? I will translate for you the question:
"What is the reading shown by the voltimeter inserted in the circuit of figure ...
0
votes
1answer
270 views
NTC 5d thermistor and how to use it
I bought a random thermistor for a circuit I'm planning to build and it turned out to be a NTC 5D-15.
I'm trying to build this test circuit:
After doing a bit of research, that thermistor resistor ...
0
votes
2answers
90 views
Voltage across a resistor in RC discharging circuit?
Problem: An RC circuit has a time constant of 68 micro-seconds. The capacitor is charged to 14 V. How much is the voltage across a resistor after 136 micro-seconds of discharge?
Attempt: What I know ...
2
votes
1answer
182 views
Current that flows through a 400 watts flat iron connected to a 220 volt power line
Problem: Find the current that flows through the filament of a 400 Watts flat iron connected to a 220 volt power line.
Attempt: The only formula I could think of that will connect voltage and current ...
1
vote
1answer
68 views
Strange issue with custom 18650 tester
Ive made my own 18650 cell tester that:
Fully charges -> fully drains -> partially charges
It takes 4 cells, measured independently of each other.
While testing the drain circuits (charging circuits ...
2
votes
2answers
96 views
Safely wiring AA batteries for consumer Arduino product
How do I safely wire AA batteries to improve an Arduino-like device lifetime?
Discussion here in the Forum [1] and the Battery University [2] suggests that using parallel AA batteries could be ...
0
votes
1answer
40 views
Working out what happens to the brightness of a bulb in a simple circuit
I have been going through some past questions for my exam that is coming up this summer. I have come across this question which I originally deemed to be easy however the more I have looked over it ...
-1
votes
1answer
51 views
What would be logic value of high impedance TTL output connected to LED
Suppose a TTL output in high impedance is connected to a LED, which is also connected to a resistor, which is then connected to ground. No circuit interferes between TTL output and LED, between LED ...
-1
votes
3answers
185 views
How to make the output of a transistor the same as the input?
I'm new to circuits in general but have a basic understanding of it. However, it seems I can't wrap my head around the following issue:
(I'm using Tinkercad Circuits for trying out different ...
0
votes
1answer
119 views
N Mosfet basics
Can somebody explain to me why this circuit will not work?
It might be that IRF3205 isn't a great choice for an Arduino but it works for Adam Welch on youtube so it should be possible. Tried it even ...
1
vote
2answers
84 views
Basic AC circuit analysis w/ wattmeter
I am having trouble dealing with this exercise. The data given is: \$U_G=110V, \: \omega=150rad/s, \: V_1=0V, \: V_2=5V, \: W=650W\$ Power factor =1.
Being the power factor equal to 1, I should be ...
-3
votes
2answers
80 views
Why would this AND gate not work? [closed]
Why would this circuit not work as it is expected to work? The IC used in this is a 7408 AND gate.
1
vote
2answers
45 views
One PSU powering one high power device & one low power device
If one was to power a (potentially) multi-amp device and an arduino with an external LM7812 12v voltage regulator to a 19v laptop charger (in parallel), would the arduino be safe when the multi-amp ...
0
votes
1answer
78 views
Basic: Current flow and grounding
I have an elementary question about current flow:
If I connect a simple 1.5 V battery to a hypothetical LED of 1.5 ohm and an ideal ammeter, the ammeter would show a current of 1 Ampere and the LED ...
0
votes
2answers
76 views
Super basic Q: How to regulate voltage in this basic circuit to avoid damaging the heating plate?
simulate this circuit – Schematic created using CircuitLab
This is for a teen-level science fair type project.
Materials include this 3V-12V generator and this 5V 1W heating plate
Goal: 12V ...
-1
votes
1answer
67 views
Determining the voltage of a network branch
[NOTE-This is a not a homework problem and i am not asking anyone to solve it]
Recently I have been simulating some basic circuit analysis problems in a simulator to get a better feel of the topic....
2
votes
1answer
384 views
Reed switch melting closed in simple LED circuit — What resistor to use?
Made a simple circuit with a reed switch, wall power source and LED strip (for a bathroom occupied sign).
Worked as I’d hoped at first. But, after a while, THE REED SWITCH MELTS CLOSED--leaving ...
2
votes
2answers
358 views
How do I find the equivalent resistance of a circuit with a node between each resistor?
I can't make out what's in series and what's in parallel in this circuit.
The solution I've thought of so far is to consider R1 in series with R4 and R2 in series with R5. Then, (R1+R4), R3 and (R2+...
-2
votes
1answer
81 views
What are important metrics of high voltage power lines? [closed]
Upfront: I am not an electrical engineer and therefore apologize upfront if I am asking a stupid question.
TLDR; What are important / relevant metrics of high voltage power lines that can be ...
2
votes
3answers
2k views
Need some help building a TL072 preamp circuit
I have an early 70's Magnavox turntable/radio console that I want to be able to plug my smartphone into so that I can use it as an external speaker. I'm plugging into the Tape In input, which is an ...
0
votes
1answer
53 views
6v switch to power something much larger [closed]
I feel like I'm making this more complicated than it has to be. If I have a 6v switch like this one, can I use it to turn on something like a 110v ~26A power supply? The current is far too high for ...
0
votes
2answers
85 views
Current Draw vs Voltage
How is it that by adding more components to a parallel circuit, the current at the root increases with no theoretical limit? Using the water flow analogy, you wouldn't find that the flow could ...
