Questions tagged [basic]

Fundamentals of electricity, electronics, components, or theory

373 questions
112 views

When you connect two batteries in series, why doesn't the middle short?

When you connect two batteries in series, why doesn't the middle short? The connection between the positive terminal on one battery and the negative terminal on the other battery has no load, so ...
38 views

Why does no current flow when GND of one battery is connected to VCC of other battery? [duplicate]

I have enough experience with electronics to design and solder working circuits. I never quite understood though why circuits must be closed for current to flow. I alway understood electrical current ...
52 views

Infrared Receiver - Simple questions regarding data sheet and basic electronics

I've purchased a 36 kHz IR receiver (TSOP38436) but I'm still learning about electronics and I'm not sure how to connect this to my micro controller (Arduino). (Also, I'm using 36 kHz instead of the ...
157 views

Does resistor placement change power dissipation in simple LED circuit?

Does the power dissipation in an LED and resistor change depending on the resistor placement? Let's assume the following: Supply Voltage: 3.3v (DC) LED Forward Voltage: 2.1v Resistor: 330 Ohm I ...
38 views

Kirchhoff Voltage Law in a two port network

In a tutorial about h parameters of a two port network, I find the below snippet in the image unable to grasp. According to KVL, the total voltage in a loop is the algebraic sum of the individual ...
45 views

PC Racing Pedals

I have very limited knowledge of electrical engineering and mechanics (I'm hoping to learn) so please forgive me if this is a stupid/noobish question. I've been thinking about making a steering wheel ...
113 views

I'm trying to understand how the charging of a plate capacitor works which lead me to question my understanding of current flow. In many explanations, it is said that the voltage source pulls the ...
8k views

Why does isolation transformer protect from shock?

Perhaps I can best explain the question with two examples: (1) there is PC powered directly from 230V mains (unprotected by RCD or similar), and there is fault in PC that causes line voltage to ...
325 views

Wire 5 vibration motors on one switch

I am trying to run five vibration motors rated at 3.7 volts each on one switch. The power will come from a 12V, 40 Amp relay on my Jeep (SPOD). How can I wire the motors all together to turn on at one ...
5k views

Where exactly does the ground line go in an AC-DC power supply?

I'm working in the United States. I'm looking into working with mains power, and I cannot for the life of me figure out where the ground line connects. For example, a simple power regulator from mains ...
770 views

Circuit analysis on op-amp with no negative feedback

In this diagram, there's an op-amp with no negative feedback. What is V+ (voltage at positive end of op-amp)? I'm self-learning circuits, and a resource I'm using says V+ = V3 / 2R. However, I don't ...
60 views

How can I determine the output in this circuit? [closed]

I have such circuit: simulate this circuit – Schematic created using CircuitLab Vin is either equal to Vcc or to 0. How do I go about determining Vout?
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I am trying to find the phase shift $\phi$ of this circuit. I am using the formula: $$\phi = arctan{\frac{X_{L}-X_{C}}{R}}$$ Substituting in the values: $$\phi = \arctan{\frac{2000\Omega-4000\... 8answers 27k views How can voltage burn out an LED? I understand how a current higher than what the LED is rated for can burn out an LED, but how does something equivalent happen with voltage? If the correct current is on an LED but the voltage is too ... 1answer 35 views 2 Possible Currents and Vdrops from same Resistor: Which Will it Be? [Beginner] simulate this circuit – Schematic created using CircuitLab Let's say I have a power supply that supplies 5v and 3A. If I add a 2 ohm resistor, it could do 2 different things. Realizing that ... 1answer 62 views How to determine the steady state voltage across two capacitors in parallel Say we have two capacitors C1 and C2, initially isolated from each other and each having an initial voltage Vc1 and Vc2 respectively, where Vc1>Vc2. When suddenly connected to each other in parallel, ... 2answers 68 views Arduino pin connection basic In the Arduino Uno's basic manual, connections for fading led are given. They have connected led on breadboard. The positive of led is connected through a resistor to the pin no 9 (pwm) and negative ... 1answer 591 views Sensing a touch of a metal Assume there is a piece of metal. I would like to identify, with a microcontroller, if another metallic object is touching this piece. I want to apply this for a smart hook that "knows" if a ... 2answers 3k views FTDI Basic Breakout - 5V Can this board be used to upload sketches to the Arduino. I tried by hooking the TX port on the FTDI Basic Breakout to RX port(Pin 2 on the Arduino) and RX port to pin 3 on the Arduino. But so far I ... 2answers 100 views Basic circuit analysis - phase shifting For the part of the circuit of sinusoidal circuit given below, the following data is given (effective values):$$E=10V,I_g=2\sqrt 3 A,I_2=2A.$$Impedance of conductor is$$Z_C=5\Omega.$$Current Ig ... 3answers 6k views Is capacitor reactance [sometimes] defined with negative sign? Wikipedia currently claims so but I've looked in 6 books via Google Books and it's not defined like that, i.e. it's just$$ X_c = \frac{1}{\omega C} = \frac{1}{2\pi f C}  Is Wikipedia full of ...
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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 "...
57 views

Basic circuit - valid pulldown

I am trying to create a circuit with multiple 5V logical control lines pulled down with 10K resistor. Is the below circuit the right answer? I can't help but feel like this will create a short ...
47 views

How does a circuit regulate current in response to a lower voltage?

Brief background, I studied physics in college and am learning EE on-the-job through Art of Electronics and this wonderful website. So this is a follow up to a previous question I submitted here ...
44 views

Basic questions on biasing

I have some trouble understanding a basic concept. Here is my question. This is from a document which can be found on the website, http://www.ti.com/lit/ug/tidu765/tidu765.pdf The text ...
1k views

How do you interpret/draw out the simplified circuits in Sedra's Microelectronics?

I legitimately do not understand how the simplified drawings in this book are meant to be interpreted. Coming from a basic circuit analysis class which had everything explicitly drawn, I'm having a ...
87 views

Voltage Drop doubt

In an ideal circuit with just a battery short circuited, where there is no resistance in the wire, why is it necessary to have resistance along the way? I understand Ohm's Law, and that the current ...
299 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, ...
74 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 ...
52 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 ...
37 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 ...
47 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 ...
4k views

How can I create an SCR using a PNP and NPN?

Several times I have seen an SCR described as similar to a PNP and NPN transistor linked together. But any attempt to replicate the idea seems to fail. In the circuit below, for example, the LED is ...
87 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 ...
120 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 ...
48 views

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?
574 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 ...
541 views

Confusion about what should be a simple resistor-divider circuit

I'm reverse engineering a circuit in some industrial equipment, and I came across some curious behavior of the input circuit... The circuit is pretty simple, it is a resistor divider with a capacitor ...
50 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 ...
128 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....
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, ...
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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 ...
238 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. ...
32 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 ...
105 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 ...
48 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
78 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 ...
1k views

Basic NFC Loop Design on PCB

I'm a college student learning the basics of NFC loop antenna design. As a starting point, I'm trying to design a PCB-based rectangular NFC loop operating at 13.56 MHz, matched to 50Ω. (NFC "...