Linked Questions

0
votes
0answers
35 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 ...
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 ...
2
votes
5answers
6k 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 ...
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 ...
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 ...
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
2answers
139 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 ...
13
votes
5answers
9k 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 ...
0
votes
1answer
597 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/...
9
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 ...
0
votes
2answers
122 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 ...
1
vote
2answers
652 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 ...
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 ...
1
vote
1answer
723 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 ...
5
votes
3answers
18k 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 ...

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