# Questions tagged [dc]

DC stands for Direct Current, which means the flow of electric charge in a single direction. Examples of a DC source are batteries, solar panels, and dynamos.

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### How can DC charge a capacitor?

I read that a capacitor shows infinite resistance towards DC. While solving questions we use DC to charge the capacitor and use a constant potential difference and current. This contradicts that DC ...
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### Control unit for 600W 12V DC camper water heater

I'm trying to build a 12V DC hot water tank for my camper. The aim is to use excess energy supplied by my 350W PV panels to heat water using a 600W heating element that is split into two connectable ...
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### Does the voltage distribution across series connected capacitors depend on initial conditions?

Assuming two capacitors C1 and C2 are connected in series and completley discharged (vc1 = 0, vc2 = 0 at time t < 0). At time t = 0, the series connection of capacitors is connected to a DC voltage ...
2k views

### DC motor pump always transports in same direction, regardless of polarity

Okay, this hurts my head: I have a vacuum pump which I salvaged and it seems to be this one: https://www.yingyidz.com/product/yyp370-xk-mirco-vacuum-pump/ I intended to get a H-Bridge motor driver, so ...
1 vote
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### Seeking product reference for an EM Noise reduction PCB Filter of DC motor [closed]

I have this DC motor (comming from an unknown bigger appliance), shown in the following photo. There is an EMI/EMC noise reduction filter soldered on it. The PCB of this filter can be seen in the ...
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1 vote
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### How does the HV supply of the MightyOhm Geiger Counter work? 555 Astable mode

Geiger counter page Full Sch PNG I know a bit about boost converter design, so Q1 switching on and off from the output of the 555 timer makes sense to me. What doesn't make sense is how the 555 ...
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### Do I need the parameters (armature current, field current etc) to do part 2?

I've completed the first part, but currently stuck on the second. Our lecturer didn't give us much to work with, so I felt completely lost trying to do this. I've been trying to complete this for a ...
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### 6 V AC conversion

I would like to know how I can get DC from the 6 V AC alternator on my moped. I have a step up booster so I think I can use any DC voltage I get but I need the DC voltage in the first place. I am just ...
63 views

### Looking for the proper solution. 36 V DC DPDT switch?

New to electronics, this may be too simple, but I’m not sure what to do. I am building a motorized beach cart using a 36 V brushed motor, motor controller and throttle, powered by (2) 20 V DeWalt tool ...
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1 vote
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### doubling up a variable 0-5V DC voltage and still being able to draw at least 100mA

I need to multiply by 2 a variable 0-5V DC voltage that has very low current capability and still be able to draw at least 100mA. So a classic opamp like TL072 is not suitable. I've got at my disposal ...
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### Need help opamp or optocoupler?

What is the best route? Optocoupler or opamp (if opamp, which one?) I need to reduce this 5.8V pulse generator to 0.84V Have an automotive application I am trying to find a solution. Basically I want ...
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### SPDT with high amps

I have 3 DC power supplies that can each supply 320 W. Input to these power supplies comes from AC wall power and is gated by an on / off switch. I have 2 different loads: DC 35 V, 22 A DC 35 V, 17 A ...
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### Tracker Accessory wiring [migrated]

I have installed a tracker into my excavator, the tracker has power, oil pump and accessory wires. The excavator has a negative isolation switch. I have connected the power wires directly to the ...
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### Relay controlling DC motor welding shut

I am controlling a fairly large DC motor using a relay. The motor draws approximately 7A at 36V. I am controlling it with a relay rated at 110VDC, 50A. To protect against back-EMF, I placed a ...
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### DC bias vs AC voltage change rate on MLCC capacitors

I'm looking at this 10uF X5R ceramic MLCC capacitor. I know that ceramic capacitors which aren't C0G have an significant variation of their value depending on voltage, temperature, aging, and ...
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### Off Grid Without Battery Inverter [closed]

Respected Members, In My Country Pakistan hundreds of peoples selling off grid inverters that are working without battery. But I am not sure whether it is safe or not? because solar production is not ...
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1 vote
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### Finding the correct power input for a battery pack powered device [closed]

I want to find the correct input voltage and current a device needs so that I can replace its battery pack with wired DC power. I suspect it's what it says on the device itself and not on the battery ...
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### I'm getting 60-130V of output from a 5V voltage regulator. Does anyone know what went wrong?

I made a 5V power supply, but when I connected my multimeter probes to the output lines of the supply it read 60-130V. the voltage after the rectifier should be around 18-19V. If anyone can give a ...
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### How should I come up with a power supply for 5 motors, one micro-controller (ESP32) and one microprocessor (Jetson Nano) for an object sorting arm

I am trying to design a power supply for a robotic arm with 5 servo motors(2 are MG90S and 3 1501MG motors). I'm planning to use an ESP32 microcontroller and Jetson Nano. I have the option of using ...
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### Transformer with same size symbol meaning

I Know these symbols mean a transformer step up or down: But what does this one represent since it has the same size on both sides? Part above taken from this schematic: And this also has me ...
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### Can one connect 2 or more DC motors of same or different excitations in series or parallel combination,and how does it work [closed]

I am trying to understand DC motors,but i had this doubt throughout the machines course. .How does speed and torques and speed gets affected(major query)
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### 18 V AC to 5 V DC circuit design with battery

I’ll start by saying I have little understanding of electronic circuits. I have an old door phone to which I have connected a wireless switch in order to be able to open my door with a remote control. ...
1 vote
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### Analysing 42v to 3.3v DC converter circuit & component identification

I'm analysing a circuit responsible for generating 3.3v for a stm32f103c8t6 on a battery management system(10s). Its a completely proprietary battery management system with nothing online about it so ...
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### Will I die or get a decent shock using an inverter?

I want to know if I can get shocked if I have the following setup? From my understanding, because the inverter (let's say a small 300W) is considered a "standalone" AC source and not ...
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### Reattaching DC power adapter jack to PCB

Recently, my baby monitor stopped charging - that is to say, when I inserted the DC power cord, I had to wiggle the plug about in the socket a bit to get in to start charging and even then it was ...
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### How to perform multiplication operation between two source voltages?

Based on this multiplication relationship table. VIN_A VIN_B VOUT -1 -1 1 -1 -0.5 0.5 -1 0 0 -1 1 -1 -0.5 -1 0.5 -0.5 -0.5 0.25 -0.5 0 0 -0.5 1 -0.5 0 -1 0 0 -0.5 0 0 0 0 0 1 0 1 -1 -1 ...
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### Replace battery by DC source (USB 5V)

I bought a Bluetooth audio receiver which is powered by 3.7V Li-ion battery. I tried to replace the battery source to a USB 5V with a buck converter and I managed to achieve it, here is my work around....
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### DC high current power supply with fast response time [closed]

I’m looking for a DC power supply that can do 100A at at least 24V but hopefully 60V. The main issue I have is that all the supplies I am looking at seem to have response times in ms where I need to ...
214 views

### Any idea what the point of this schematic is in the DC section?

The schematic below is taken out of an actual PCB. The motor is connected to the top (+-) but from the schematic it appears it is connected to the AC portion of the rectifier. What is totally unclear: ...
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### D-cell Ni-Mh 12v battery-pack (10S) ok for a 12v device that can be a little heavier/bulkier?

In a previous question I was asking about a way to use dc charging in combo with an 18650 battery pack for an audiobox. Since site rules mean I cannot change or add to that question after it has been ...
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### Can I charge my 3S2P 18650 battery (12.6v) with a normal 12v power adapter if I use a BMS with built-in balancing+protection? [closed]

First off, I would like to stress the fact that I am no electrical engineer or anything of the sort, just a hobbyist that is into this kind of stuff. So please bear with me, as I know a few things ...
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### Can this circuit be used for an AC-DC emergency LED lamp?

Basically, this circuit is supposed to light the LED lamp from either AC or the battery. When there is AC available the bulb will glow with the power of AC and the battery will be simultaneously ...
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### Are small analog signals more or less susceptible to interference with a DC offset applied?

Per the title--when looking at analog instrumentation signals ("AC" for this purpose) traveling over a cable (in the realm of say 1-2Vpp) are those signals more or less likely to be impacted ...
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### Questions About My Perpetual Motion Idea [closed]

Before you read any of this, this is just an idea. I am not an electrician, I am not a contractor, I am not a physicist, or anything like that. I just have an idea that i think could possibly work. I ...
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### Purpose of this RSNUB

This image is from the schematic of an overvoltage protection regulator. https://www.analog.com/media/en/technical-documentation/eval-board-schematic/1018babcsch.pdf I'm trying to find out the ...
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### Does LC circuit convert DC to AC?

I was experimenting with LC circuit (Class 12 - Physics, India) in CircuitJS1 Simmulator. Interestingly, the LC circuit given below was converting DC into AC. Circuit: Circuit Specifications: DC ...
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### Ayrton Shunt/Universal Shunt

Is it correct that I calculated Rs for every range; 0-100mA, 0-150mA and 0-300mA? Then, to find R2, I need to do Rs=R2+R3+R4? Like R2=Rs-(R3+R4)?
1 vote
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### Can I use an AC SCR to control a 180 V DC motor?

I want to control the speed of a 180 V treadmill DC motor the cheapest and easiest way. The motor will only run in one direction. It wil be powered by 220 V AC. Can I use an AC SCR speed controller ...
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### What is the easiest way to turn 1 kV DC to 10 kV DC?

What is the simplest method for me to take quick 1 kV DC pulses, and turn them into 10 kV DC pulses or higher? What might my circuit look like? Edit to provide more detail: Water rolling down a short ...
1 vote
1k views

### Capacitor connected with a DC source

Here is the pure capacitor connected with a pure DC source. The moment switch is closed all the voltage of the source will appear at the capacitor plates causing the current to flow. I wonder what ...
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### What is the scope of this circuit? [closed]

I was looking at a schematic block, for an VIn for an ADC and I saw this : What is the possible scope for this block?
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### I obliterated a ceramic SMD, how to find out what piece it is?

this is from a laser GRBL generic from China, 12v and 5v. The neighbor SMD appears identical to the one that was cracked. The multimeter measured 1.0 mega and milliohms, I couldn't get a reading. Do ...
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1 vote
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### Calculate resistance between 1 and 2

I am preparing for an electrical engineering exam coming up and I got stuck on task C, where you have to determine the resistance between 1 and 2. How do you do that exactly? I have already solved ...
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### What's the name of the device that reverses on-off state based on second power input on-off?

Specifically what I'd like to achieve is find an electronic switch that connects to a car's ignition system and that has a second circuit in it that is kept active (on) when the ignition is off, and ...
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### Step-down, ultra-low current kVDC and boosting current [closed]

I have a constant current source that can only give a maximum of 1 μA DC but can maintain this current level from less than 1 V to a few thousand volts, depending on the resistive load. I calculated ...
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### DC Motor Problem Explanation

Can someone explain to me how we got the values for Id and Ud, also how we got that speed and current in armature? The reference for this problem is our professor's chalkboard. I copied it in my paper ...
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### How to get the drain-source voltages of cascode MOSFETS?

I have a question about operating point of cascaded NFETs that I carry with me quite some time. I hope someone is able to give me some hints or insights here. It boils down to this: When you have a ...
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### Resistors for a Solid State Relay

I have a controller output fused at 250 mA, and I need to use that output to switch a 1.5 A load. Everything is 12 VDC in the vehicle. Figured I'd be using a solid state relay. Do I need to be worried ...
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I have a set of hardware that needs a power supply of 120 watts. I understand that Power is Current times Voltage or: $$P=VI$$ If I were to purchase a 13.8 V, 15 amp DC power supply, or a 13.8 V 50 ...