# Tagged Questions

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### I want to build a portable railgun and I'm a complete rookie [closed]

I'd like to enter the world of electronic hobbies by making a railgun, and so far I know that I understand the basics of the device and that I need high amounts of direct current. However, I am ...
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### 220V 0.2A converted to 12V 5A, where are the missing amperes?

I have an AC adapter at home that reads (roughly) the following: uses 220-240v AC 50Hz at 0.2A produces 12V DC at 5A I'm a little surprised that it uses 0.2 amps and produces upto 5. Here's what ...
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### Low current battery monitoring

I want to run a micro-controller from a 1S lipo through a 3V linear regulator. I need to measure the battery voltage however. The problem with using a voltage divider is that it would drain the ...
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### Electricity Existing in Wire

I'm a programmer, and I usually hang out over on stack overflow, but I have a electricity question. I'm trying to interact with an APP on my phone by indirectly touching the the screen. Modern ...
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### Android phone USB charging has a mind of its own [closed]

I have a Sony Xperia phone. I have 2 USB-to-USB-micro cables, a power charge-only one and a data/charge one. I connect the phone to my PC to charge the phone. When the PC is on, both cables charge ...
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### Why does conventional electricity flow out of + in a battery, but out of - in components?

It seems like when electricity flows out of + in a battery it should be attracted by a - end of a component, but it's not like that. Why?
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### Need chargeable momentary 15 watt regulated voltage source

I'm working on a RF telemetry side-project that requires an amplifier IC to be run for about 5 seconds bursts between charges. The system is portable and runs off of a 3.3V battery that can supply ...
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### What parameters affect battery charge time?

What parameters affect battery charge time? For example if we're interested in designing a charger for mobile batteries, what parameters should be considered? What happens if a little higher voltage ...
121 views

### how to charge a steel ball

I have a 2 mm radius steel ball and I want to charge it in a 0.025 Coulomb charge. Can I do that domestically or the charge is too high? And how can I do that assuming I don't have another conductive ...
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### Calculating induced charge

Let's say I have a battery with V volts. A conductive material (Material A) is connected only to the battery's positive terminal. Material A is then connected to a second conductive material (Material ...
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### Voltage requirements for charging Nokia phone

I have an old Nokia phone which charges fine from the adaptor, but refuses to charge using a USB charging cable. Note that this isn't a normal USB cable, as you can see from the picture, it's got a ...
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### Understanding voltage and current

While reading "Electronics for dummies" went through the following block and I realised that I have some uncleared concepts about electricity: Electrostatic discharge involves very high voltages ...
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### Questions about capacitors in DC

1.Does the current flow through the capacitor when (a) it's not charged, (b) it's partially charged, (c) it's fully charged ? How does the flow changes in time (ex.: exponentially, logarithmically, ...
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### Why is the Anode positive if Anions are negative…?

When I was younger I learned in Chemistry class that Anions were negatively charged and Cations were positively charged (Fun fact: I memorized this because anion sounds like onion which makes you cry ...
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### Charge moves if you scuff the rag with your shoes [closed]

Why is that when you scuff with your shoes on, charges move (since electrometer moves back and forth), but if you dont have your shoes on, the electrometer doesnt move Here is the corresponding video ...
1k views

### Need help driving N FET gate from LM393 comparator output

I am working on a charge controller circuit idea I had. The circuit 'works' meaning it achieved desired output voltage but the fet doesn't seem to be turning all the way on so lots of heat is ...
428 views

### Charging 35V 470uf capacitor with coin cell

I want to charge a 50V 470uF capacitor up to 35V with the smallest battery possible. Can a coin cell do this 3000 times? Possibly a 2450 or 2477 coin cell? Also, can the capacitor be fully charged ...
286 views

### How to impart a charge on dust particles?

I am planning on building a simple electrostatic air filter, from scratch. From what I understand, the dust in the air is given a charge as it flows through an inlet section and is collected by mesh ...
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### charging and discharging capacitors

I'm wondering if it's possible to charge say a capacitor with a stepper motor (~12V DC after rectifying), which when it reaches its maximum capacity discharges. I'd like the discharged power to ...
223 views

### Generating Strong Electric Fields

What is the best way of generating strong, steady, electric fields (E) using the tools and voltages available to the home hobbyist? Is it better to using electrostatic sources like a Van de Graaff ...
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### How and when can solar charge controllers be stacked together?

I run a small busniness selling solar charge controllers. Often I have a problem with not having controllers rated high enough amp-wise. I know that charge controllers can be stacked. But can all be ...
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### Battery charge indicator LEDs

Many laptop batteries have a button on the bottom that will light up 1-4 LEDs to indicate how much power is remaining. I'd love to build something like that into my own device, which is powered by 2 ...
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### Voltage used to charge a UPS-Inverter and its usage

I'm new to this area and know very little about electrons and how electrical components work. I'm always curious about Inverter/UPS usage. I'm from India and we have a inverter at home. It is ...