Linked Questions

13
votes
5answers
10k views

How does a USB 2.0 Wall Charger negotiate current output?

I'm trying to use a mobile phone charger for my projects, and want a high current output. I have read this, however my measurements show something else. Here is a link to the Battery Charging ...
10
votes
6answers
1k views

USB Power - The basics

I am new to designing something to be powered by USB. Ideally It can either be plugged in to an adapter to a UK wall plug, or a powered USB port on another device. I have the circuit design in place ...
8
votes
3answers
2k views

Best way of making a battery powered USB charger?

I recently made a USB charger that takes a 9V battery. I've noticed it doesn't work with a lot of devices though. It was very simple though, just a 5volt regulator hooked to a USB plug and 9V battery ...
6
votes
2answers
4k views

Critique of my Data logger's Power circuit design

I am laying out my first full device, a fairly simple sensor-data logger, with these specs in mind: I'm running microcontroller and sensor @ 3.3V, with load varying from 10 mA to 400 mA device will ...
5
votes
3answers
19k views

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 ...
4
votes
3answers
1k views

What's needed to get 100 mA from a USB port?

I'm trying to build a stereo speaker system for use on a laptop. I want to keep it as simple as possible, so I'm thinking of using laptop's audio output to for the audio signal and a USB port for ...
3
votes
1answer
217 views

What's the DC voltage range typically tolerated by modern smartphones?

The modern USB charging circuitry of mobile phones is pretty sophisticated. For example they can negotiate higher charging voltages etc. This question, inspired by a discussion on worldbuilding, is ...
3
votes
3answers
1k views

Connecting a higher-current power supply to a lithium-ion charger will damage the battery. Why?

I am not asking how the battery gets damaged, because that answer is straightfoward. What I am asking is why lithium-ion chargers allow batteries to be damaged by excessive charge current in the ...
3
votes
2answers
632 views

Lengthen a AC to microUSB phone charger cord?

Can I effectively take a 3 ft standard cell phone charger (AC to microUSB, 750 mA at 5V) and lengthen the cord to 6 ft by splicing the cord or am I going to lose something in the mix? Do I need to ...
3
votes
2answers
6k views

Make a tea mug heater with a USB power source

For a school project, I have to make a mug heater which draws its power from a computer's USB port, such as this one. I don't mean one that boils the tea, but one that keeps it warm-ish, at at least ...
3
votes
1answer
8k views

How does my phone get charged via laptop USB port at lesser current (compared to wall charger) [duplicate]

Today's typical smartphone chargers are rated at 5 Volt & 1+ Ampere. The laptop USB can supply 500mA 100mA. Why is it safe to charge the phone with 1/2 the rated current? Is it like a slow ...
2
votes
2answers
383 views

connect LEDs to USB keyboard – but they turn off after a second

I have a USB keyboard. As I work many times in the darkness, I put some LEDs into the keyboard case. I connected two pairs of yellow standard LEDs serially to the USB power lines (Vcc and ground, pin ...
2
votes
3answers
2k views

Feeding 2*5V to a 12V fan?

How would I amend a 12V fan to take 2*5V? The 12V fan has 2 wires on it. one would take 12V the other GND. I'd like to be able to feed it 5V and 5V, instead of just 12V. What do I need to do it? ...
2
votes
5answers
8k views

How to adapt a string of 10 LEDs powered by 3 AA batteries to work off a USB port?

I have a string of Christmas lights made up of 10 warm white LEDs. The lights are connected in parallel (not in series). The string works with 3 AA batteries (that is, 4.5 VDC). And all that stands ...
2
votes
1answer
2k views

Risk of overloading a usb charger

I just bought this product: "Jackson PT1USB" as an attemp to get a portable charger for my netbook, ipad 2 and smartphone. Now I am bit worried after reading in the product "total connected load to ...
2
votes
4answers
4k views

Max current for USB powered Arduino?

My plan is to use a Teensy logic output pin to switch a transistor to switch an infrared LED The LED handles up to 1A peak current. I will use it as a computerized IR remote transmitter so the duty ...
2
votes
2answers
1k views

Convert low power USB to high power USB in car stereo.

Could I connect the D+ and D- to my car stereo's USB input, then connect the red and brown (+/-) to a 2amp cigarette plu'sg USB? My issue is that the USB in the head unit is low power and doesn't ...
2
votes
2answers
453 views

Can you charge a battery to run a device at 5V from the USB port?

Say you had a device that requires 5VDC to operate. It can actually run safely at about 4.8VDC. It normally runs off of USB power but I would like to rig it up to run off of a battery. Would it be ...
1
vote
2answers
693 views

How much current will I get from the 5V rail of a Teensy 3.2 powered over USB? [duplicate]

The microcontroller in question is a Teensy 3.2. My understanding is that the most current that you can get from a standard computer USB port is ~180mA; how much of that will current devices attached ...
1
vote
1answer
815 views

How to configure USB OTG as power supply

I have an ARM computer with an USB 2.0 OTG port, and I want to use it as 5V 100mA power supply (to drive a couple of leds). However, when I connect a load (LED+resistor) via an OTG cable, the power is ...
0
votes
4answers
4k views

USB PC Current Limit

I want to build a USB device that can draw 1A. Some of the PCs at my office can supply 1A, some only 800mA. The USB 2.0 specification says a device can only draw up to 500mA. I cannot build a ...
0
votes
3answers
1k views

Why USB wall chargers don't reach their amperage rating? [closed]

recently I bought a power bank that requires 1,6A of charge current. I tried charging it with a 2A Samsung charger, which came with my tablet. Unfortunately it charges very slow. Then I tried another ...
0
votes
4answers
2k views

Creating Li-Ion charger with step up to 700mA from 500mA?

Canon apparently hasn't ever herd of something called USB-charging. The factory AC adapter for this battery(NB-5L) output's 4.2V's at 700mA. Most standard USB chargers output 5V at only 500mA. Would ...
0
votes
1answer
653 views

LM317 to charge a NImh battery from usb [closed]

Hi want to charge my 4000 mAh 1.2V nimh cell battery simply, I do not use them very often. So I wanted to plug this kind of voltage regulator which I think is like that : https://en.wikipedia.org/...
0
votes
2answers
126 views

USB powering batteries without OS support?

On a bare-metal project I have in mind, I would like to know if I can avoid to implement the multiple USB specs (O/E/xHCI) and still benefit from usb charging my battery. It will run on a almost ...
0
votes
3answers
3k views

Three-prong / USB power outlets in wooden desk [closed]

I am trying to mount a strip of three-prong outlets and a strip of USB charging outlets on an old wooden desk. I can handle the carpentry aspect, but I am struggling with the electrical aspect. I ...
0
votes
3answers
51 views

USB 2.0 High-Power Circuit

Is there are special circuit that says to USB socket how much current the device needs? Our device needs at up to 200mA or little bit more. I have been searching but I do not find a clear answer ...
0
votes
2answers
144 views

Drawing too little current from PC USB

If I connect this very small load (3 LEDs) to a mains to USB adapter, it's fine. Full brightness, great. I can't even measure the current it's so low. However, if I connect it to my PC it does 3 ...
0
votes
0answers
60 views

Usb charger not charging only with vcc and gnd [duplicate]

I want to charge my tablet on the wall. And I have a charger behind the tablet and connected 2 wires to vcc and gnd, the same pins as usb female, it turns out that I can't have more than 10 mA. If I ...
-2
votes
1answer
1k views

Can I use my Android tablet charger for the PlayBook? [closed]

I got a BlackBerry PlayBook and it came with the wrong charger plug. It's for the US that I can't use here in Germany. Can I use my Android tablet charger for the PlayBook instead? The information ...