# basic's questions - English 1answer

335 basic questions.

### 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 ...

### 3 What's the rationale behind these warnings about extension cords?

6 answers, 217 views cables heat basic theory
(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 A few basic questions about simple electric circuits

2 answers, 162 views ac dc basic
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 ...

### 1 How do you model a “leaky inductor”?

2 answers, 87 views capacitor inductor basic
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 ...

### Wire 5 vibration motors on one switch

2 answers, 207 views circuit-design wiring basic
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 ...

### 35 What is a Charge?

10 answers, 4.960 views computers basic charge books
I'm a high school student. I love computers and electronics. Few weeks ago, I thought to build my own electronic gadget but, unfortunately I had not much knowledge in electronics. So, I decided to ...

### 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 Understanding this circuit with op. amps

1 answers, 692 views op-amp basic
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 ...

### Figuring out if an led strip/matrix has a short or not with a multimeter

2 answers, 22 views led multimeter basic continuity
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 Basic question I would like to be solved

2 answers, 97 views circuit-analysis basic
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 ...

### NTC 5d thermistor and how to use it

1 answers, 65 views arduino resistors basic thermistor
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 ...

### Voltage across a resistor in RC discharging circuit?

2 answers, 31 views capacitor basic electricity
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 Current that flows through a 400 watts flat iron connected to a 220 volt power line

1 answers, 74 views basic electricity
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 Strange issue with custom 18650 tester

1 answers, 66 views wiring basic component-selection
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 Safely wiring AA batteries for consumer Arduino product

2 answers, 91 views power batteries basic
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 ...

### 5 Why would we need to ground an AC source?

3 answers, 12.660 views ac basic
I'm new to this field hence this weird question. Why would we need to ground an AC source? Why wouldn't it be enough to have just one pole to get an AC current going? I understand why it wouldn't work ...

### Working out what happens to the brightness of a bulb in a simple circuit

1 answers, 31 views circuit-analysis basic
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 Understanding an N-JFET

2 answers, 282 views basic jfet
I am currently learning about FET transistors, and there is some things that I do not understand about an n-type JFET. I have two question about this transistor. Why is Vgs important and how do we ...

### -1 What would be logic value of high impedance TTL output connected to LED

1 answers, 40 views basic ttl high-impedance
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 How to make the output of a transistor the same as the input?

3 answers, 150 views transistors basic
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 ...

### N Mosfet basics

1 answers, 113 views arduino mosfet basic
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 ...

### If Conventional Current is wrong, how can I trace the flow of current in a schematic?

5 answers, 767 views current basic
If Conventional Current is backwards, how do I look at something like this schematic and trace the flow of current? I'd like to follow the design linearly from positive to negative. When the battery ...

### 1 Basic AC circuit analysis w/ wattmeter

2 answers, 57 views circuit-analysis ac basic
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 Why would this AND gate not work? [closed]

2 answers, 71 views digital-logic logic-gates basic
Why would this circuit not work as it is expected to work? The IC used in this is a 7408 AND gate.

### 1 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 ...

### 2 Op amp design that gives \$V_{out} = -2 *V_{1} + 3*V_{2} - 3 V_{3}\$

3 answers, 3.982 views op-amp basic
I know that a regular summing amplifier does \$\ V_{out} = -(a*V1 + b*V2 + c*V3)\$ but how do I invert one of the gains?

### Basic: Current flow and grounding

1 answers, 68 views batteries ground basic
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 ...

### Super basic Q: How to regulate voltage in this basic circuit to avoid damaging the heating plate?

2 answers, 75 views voltage voltage-regulator basic
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 Determining the voltage of a network branch

1 answers, 42 views voltage circuit-analysis basic network
[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 Reed switch melting closed in simple LED circuit — What resistor to use?

1 answers, 245 views resistors led-strip basic reed
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 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 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 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 ...

### 3 Can I determine the original resistance of a burnt/failed resistor?

5 answers, 13.497 views power-supply basic
How to find the (original) value of a burnt resistor? Let's suppose a condition in which initially I don't know the value of its resistance. Now because of its low watt, it burnt. So is there any ...

### 6v switch to power something much larger [closed]

1 answers, 52 views power-supply power switches switching basic
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 ...

### If we put a led light into a oscillating current, will it blink?

4 answers, 167 views basic logic-gates
Sorry for the misleading title cause I have no electronic knowledge. It is a simple question. This is the circuit diagram. In case you don't see clearly, it is XOR GATE. My question is what will ...

### 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 ...

### Fan not working on motherboard even if same voltage works with batteries [closed]

2 answers, 142 views voltage current basic cases
First of all I want to mention that I have no knowledge electrical field, so please forgive me if I will not be explicitly enough or I lack some terms, but I know no one with knowledge about ...

### Help Using a MOSFET

1 answers, 81 views mosfet switches basic switching powermosfet
I have an N-channel MOSFET, part number IXFH30N50P. I am trying to use it as a switch for a 320V 8100uF capacitor bank. My idea is that I would have a separate, small voltage source, like a battery, ...

### Is the FET gate resistance counted on the RC time constant?

1 answers, 70 views capacitance basic fet
As I understand, a logic "1" output to an input of another IC can be modeled like this : simulate this circuit – Schematic created using CircuitLab with C1 representing output capacitance, R1 ...

### 2 Static electricity discharge, what gets transfered?

Ive been studying Maxwell equations at school and I solved several excercises regarding electrostatic fields, however, I still have some very basic unanswered questions: When a non conductive object ...

### 1 Calculate voltage over resistor

I have a problem when calculating voltage over resistor because one method worked for one problem but not the next. I solved (b) like this: $$12-4=8V$$ $$8*\frac{60}{60+20}=6V$$ $$V2 = 6V+4V=10V$$ ...

### Can a short circuit damage nearby devices? [closed]

This happened yesterday and left me scratching my head. We had a badly built power extension cord in our office. Inside it has 3 wires - live, zero and ground (hope I got the terminology right). When ...

### 2 LM317T outputs current on Adjust pin with nothing connected between adjust and Vout?

1 answers, 96 views basic constant-current lm317
I have a LM317T-based simple circuit and I'm using a 12V battery to power it. I connected the Vin to + 12V and made a constant current circuit as shown here. Now, I'm using a variable resistor of 100k ...

### 3 Why does isolation transformer protect from shock?

4 answers, 5.793 views transformer basic physics 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 ...

### 4 Confusion about what should be a simple resistor-divider circuit

2 answers, 237 views resistors opto-isolator basic
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 ...

### Connecting capacitor to the ground and potentials question

0 answers, 53 views basic theory electricity
I am a newbie trying to enter the world of electronics and currently struggling with getting a good grasp of basic concepts of electricity. I understand that electrons which usually produce the ...

### 1 How to achieve desired output voltage and current draw from a hot shoe

1 answers, 58 views power-supply basic
I have very little knowledge of electronics, although I enjoy tinkering with basic electronics from time to time. If I have a battery of known voltage and I want it to light up a small 3mm led, I know ...

### 1 Combine two circuits

I want to apologize in advance for any ignorance throughout this post, I'm not anywhere near an electrical engineer. Basically I have a consumer which requires 220v and is not operating all the time. ...

### 2 How does a first-timer set up a correctly-grounded workbench / work-station?

1 answers, 3.444 views basic grounding groundloops workbench
I'm new here, and new to electronics in general. (for the most part … my [awesome] father had me building some simple Heathkit robots and panels with him when I was a kiddo, but I'm getting into it “...