Tagged Questions

Voltage, otherwise known as electrical potential difference (denoted ∆V and measured in volts) is the difference in electric potential between two points (adapted from Wikipedia). Voltage can be constant (DC) or varying (AC).

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Calculation Inductance Voltage in book 'Practical Electronics for Inventors'

I'm curious is calculation in screen right? I assume Voltage from 2-3 sec must be -0.2V, because dI/dt=(-1)-1=-2A, not -1A. Am I right?
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How does a transistor behave when the gate is disconnected?

On an n-type transistor, if a voltage above a certain threshold is applied to the gate, current can flow from source to drain. On a p-type transistor, if a voltage below a certain threshold is ...
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How to build 5W LED bulb circuit from 230V 50Hz main AC supply with and without Transformers? [on hold]

Please answer with circuit diagram with all values or give me the link.Tell me the efficiency also. Thank u...
352 views

Can I measure voltage and current at the same time by using two multimeters?

I think the title is revealing. I'm planning to use 2 multi-meters to get a better perspective of my circuits. Is there any drawback in this situation i should be aware?
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MOSFET Drain Voltage

I am trying to simulate a single NMOS, I calculate the I_ds but I need the voltage of the drain terminal. Should I multiply the I_ds value by a resistance value? Is this resistance constant? If not ...
60 views

Can I use a 12v battery to power a class 2 transformer (120v input 15v output )? [on hold]

I'm attempting to use old computer speakers ( Altec Lansing) and make a mobile speaker system,but I'm unsure if I can connect the transformer that came with it to power it using a 12 v ( small, like ...
37 views

Measuring the voltage between (positive/negative) terminals of PV cell and ground

I tried to measure the voltage between positive/negative terminals of a PV cell and ground while the cell was exposed to the sun, I found that the voltage decreases with time -the PV cells were ...
76 views

Get -50V to 50V range from battery output

I have the following problem: on the system which is battery-powered(4S1P Li-ion battery, 14.8V) I need to create outputs from -50V to 50V. The system has microcontroller on-board. I am baffled on ...
85 views

Could gravity waves generate electricity in metal? [on hold]

If gravity waves passed through a metal sheet or wire could it generate current or voltage because of squeezing and stretching. OR could it generate voltage because of single charge it possess.
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Body interference in my analog multiplexer, maybe AC electromagnetism induction?

I just wired a CD74HC4067 analog/digital multiplexer to a matrix of leds. The multiplexer is wired to control the LEDs, and is connected to an arduino board, which is connected via USB to my macbook ...
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1-2kW solar voltage regulator cca 28.9V to 24V DC stable [on hold]

I've got several solar panels simillar to these http://www.solardesigntool.com/components/module-panel-solar/BP/984/BP3220T/specification-data-sheet.html Each panel is rated 28.9V 7.26A (max 210W) ...
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OP AMP CONVERT CURRENT TO VOLTAGE

I see in a schematic , a op amp(lf357 or lf411)convert current to voltage amplifier .(current come from a loop of wire) . Now I want implement that circuit with LT1468. but not work correctly. what ...
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Energy stored in the capacitor increase when the capacitance decrease [on hold]

Help!!!!Energy stored in the capacitor increase when the capacitance decrease.Suggest an explanation for this energy increase, making reference to conservation of energy. Question [paper 3,Q4(D)(ii)] ...
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Ni-MH battery voltage [duplicate]

I have a battery pack of 8 Ni-MH 2400 mAh cells connected to a load that draws ~700 mAh (a Raspberry Pi Zero, display, WiFi dongle, USB hub, and a wireless keyboard dongle). I want to add a led that ...
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Voltage distribution in IC in MATLAB Simulink

I tried to simulate the IC IR2121 using simulink. I am trying to test the IC that I simulated. When I connect the voltage source directly to the Vcc, it gives an error stating that the current ...
107 views

Voltage across a 2.2k resistor [on hold]

I've just begun learning about electronics, and have been performing a few experiments on measuring voltage,current with a multi-meter. If I have a single resistor having a resistance of 2.2k ...
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I'm looking at high channel multiplexers that can operate at voltages over 10V and for this component it says that the supply voltage is 12V which is okay for my application, but when you read under ...
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Can I reduce voltage of an led?

I'm still new to electronics, so beae with me. Luckily it's a short question: I'm following a schematic that calls for a 1.7-1.8v led, but unfortunately I only have 3v 20mA LEDs.. Is there any way I ...
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Using pot as variable resistor: should wiper be connected to spare end terminal?

I've heard somewhere that a rheostat uses two pins while a potentiometer uses three. But still, the thing i would like to know is if there's anything different with the adjustment if I wire the pots ...
73 views

Identify black component in Gopro 3 silver [closed]

Can anyone tell me what this component with a red square around is? As you can see, the one right next to it is burned, and I would like to replace it. I have attched a schematic of the Black PSU it ...
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RF/voltage clamp/limiter [closed]

I'm looking for a circuit that is called "RF clamp", "RF limiter", "voltage clamp" or "voltage limiter". The example of such circuit is a transistor Q on this picture: However, what I need is a ...
68 views

Learning by doing - Fixing Turntable [closed]

I recently moved from Canada to Amsterdam. I blew my Stanton t.92 turntable (TT) by plugging it into the mains with a travel adapter (I know, lesson learned). Looking on the bright side I am using ...
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AGC which tells you what gain its at?

I am looking for an AGC (Automatic Gain Control) which outputs not only the normal output but also another output which tells you what gain it is using. I need this for an automatic voltage meter I am ...
74 views

Maximum current through an LED

I have these LEDs for which the max current was not specified. However I know that the voltage is 3.2V-3.6V and the power is 1W. Is it correct to assume that the maximum current is therefore 0.27A ? ...
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Stepping up voltage from solar for a power brick (5V to 15V) possible?

i have a 28mAh power brick capable of charging my laptop when charged. I bought a 28W solar panel which outputs 5V over usb capable of charging ipads etc, however when i connected it to power brick's ...
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why leading power factor cause rising system voltage?

why leading power factor will cause rising voltage? how can it happen in mathematical calculation? i think the voltage in power factor correction will be stable but the current will change because of ...
118 views

Can I just add cells to a solar panel to prevent voltage drop?

I have a solar panel which should be putting out 12.5v and 30 amps which has 100 solar cells, but I recently discovered it needs to be 17v or so because the voltage will drop. If I add 11 0.5 volt ...
191 views

Different voltage drop in serial and parallel circuit with resistor

I have a circuit powered by 9V battery, I'm using two 2V LEDs. If I connect the LEDs in series with 10k Ohm resistor, the voltage before resistor is 9V, after the resistor it's 3.3V and after the ...
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Beaglebone black does not enumerate over serial connection

My setup : Ubuntu 14.04 LTS dual boot with windows 7. I connected usb power cable which is a 5 volt supply. I also connected a usb to uart serial cable, and was able to see this to be as ttyUSB0 in ...
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12v solar panel li-ion charger

I'm planning to use two 6v 0.6W solar panel in series to supply a cheap tp4056 module with builtin cell protection in order to charge a single li-ion battery. In order to regulate the voltage to 5v ...
305 views

When you have one resistor in a series circuit, the amount of voltage taken up by that resistor is 100%. Adding another resistor (same Ohms) makes that voltage drop 50%. Why, since only current should ...
77 views

How to power ESP8266 from changing voltage

So I'm very new to electronics of all sorts, have done some basic repairs but I'm interested in learning more. The project I have in mind is to use the cheap and easily available Doit NodeMcu Lua ...
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What is difference between 2 transformers rated to give output the same voltage but different current (ampere)?

What is difference between 2 transformers rated to give output the same voltage but different current (ampere)? Such as, if a stepdown transformer is rated as 12V 600mA, and another is rated as 12V ...
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What Resistor Should I Use? [closed]

I have an 18V battery and a 12V bulb and I want to reduce the voltage with resistors. I have already used a transistor (L7812CV) which works fine but now I want to know how to do it with a resistor so ...
6k views

Is voltage the speed of electrons?

Current is the amount of electrons passing through a wire. Can we say that voltage is the speed of those electrons?
37 views

voltage selector circuit for programming microcontrollers

I have a microcontroller that has a VPP pin which requires 12 volts to enable programming mode, 5 volts for normal mode, and 0 volts for reset, and I want to achieve all these modes without manually ...
54 views

What is the significance of the current rating of a power source?

Assume, I have a copper coil (solenoid) with exactly 1000 turns. When I connect a multimeter across the 2 ends of the coil, the multimeter gives a resistance value of 20 ohms. Now I have 2 power ...
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Voltage measurement circuit

I have a material and I want to measure the voltage and current through it over time. Unfortunately I only have an automatic voltmeter and the resistance of the material changes over time. Because I ...
92 views

Switching on and off high 50V DC circuit?

I'm having a little trouble finding a way to activate my circuit. I don't have a proper circuit drawing tool available however hopefully my drawing from MS Paint will do. //////////////////////////...
549 views

Does running LED at higher voltage damages the LED?

I want to run 12v 6 watt LED at 19v by keeping maximum watts constant (current controlled). By doing so will damage the LED? I.e 12v x 0.5000 A = 6W 19v x 0.3157 A = 6W update1: I am ...
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Did I correctly use the Voltage divider rule to derive the transfer function?

Question and diagram are on link and NOTICE Rs is assumed to be a short. I believe the transfer function is going to be: A(jw) = 1/(jw*C1*R3+1) I arrived at this answer by using a simple voltage ...
69 views

Two batteries in parallel by a long cable

I want to build a system where I have a solar charger connected to one 12V battery, which is then wired in parallel by a long cable (30 meter, 2.5 mm2) to the other battery. Will both batteries ...
74 views

12V voltage drop over long wire

I have a cabin which is running off grid, using a solar panel and a (2*120 Ah 12V) battery. I now want power in another building 20 meters away. One solution is to use an expensive high gauge (7 mm2)...
531 views

Why is an infinitely large capacitor a DC open circuit?

This really sounds like a stupid question, but I believe it's worth asking: Due to $I=C\frac{dU}{dt}$, and $C$ is infinitely large, any minor change in $U$ would result in infinite ...
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Voltage divider before the input of an LM324N used as a comparator

simulate this circuit – Schematic created using CircuitLab I am designing a driving system to control some servomotors, and since my microcontroller can not drive enough current, I had thought ...
871 views

I was explaining a transistor to someone, and I realized: I don't really understand several key concepts at a low level. Help?

(Surplus story removed.) I was explaining MOSFETs, CMOS, and logic gates to someone and realized I didn't grasp some concepts as well as I thought. It culminated when he drew a single transistor, ...
59 views

Start a dead battery car with a power/USB charger [migrated]

today my car couldn't start beacuse of dead battery. The battery is not old, I simply left my dash cam attached for a few days without using the car... I'm alone at home and my car is in a difficult ...
60 views

Is it bad to put 3.7V on 3V mice? [migrated]

I have mouse that take two AAA batteris, so it take 3V. Is it OK put one 10440 of 3.7V and one spacer instead?