Linked Questions

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
2answers
626 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 ...
2
votes
2answers
370 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
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
447 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
674 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 ...
0
votes
2answers
142 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
2answers
123 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 ...
3
votes
1answer
206 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
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
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 ...
1
vote
1answer
746 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
1answer
628 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/...
-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 ...
0
votes
0answers
42 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 ...

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