Tagged Questions

3
votes
1answer
105 views

Safely extract power from USB

I am upgrading the lighting in a model with simple circuit which has 17 LEDs (approximately) plus one or two 555 timers. Presently, everything is powered by 3 AAA batteries. It drains between 150 and ...
0
votes
3answers
116 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 ...
-5
votes
2answers
81 views

What is the range of a 2dB usb wifi dongle? [closed]

For a home robotics project I need to connect my laptop to my robot's Raspberry Pi using wifi. For this to work I want to buy a simple usb wifi adapter to plug into my Raspi. I will need a range of ...
3
votes
1answer
166 views

Separating USB/MCU power buses

There are two power supply sources in the following diagram - USB and 12V. Only one power supply can be connected at the same time. I am trying to disable power to ...
6
votes
1answer
186 views

Is it possible to make a power auto-selector (ORing) with just a Diode and Mosfet?

I know there are ways to create a simple auto-selector using a mosfet and op-amp, or even simpler using just Diodes, but is it possible to have this work: The mosfet is P-Channel so floating gate ...
-1
votes
1answer
77 views

GSM Power Supply

http://www.powersystemsdesign.com/usb-modem-design Can anyone tell me how the energy values in the table are calculated in the link above,
1
vote
2answers
176 views

Properly testing a USB power supply

I've recently bought 5V/1A USB power supplies, and since the packaging was slightly damaged (specified in the auction I bought it from), I thought about testing it before connecting to anything ...
1
vote
3answers
664 views

7805 Regulated DC Power for two devices

I need to create a circuit specifically for powering two devices. These devices include a device, which has to be powered via 5V USB and another device which has to be powered with at least 6V (all ...
1
vote
2answers
223 views

How realistic is a 4 ports charging only USB hub mount inside a wall outlet box?

Here's a concept of a wall outlet variation. It's size of a wall outlet (occupies the same size standard box in a wall) but instead of mains outlet it has four USB ports for charging various devices. ...
2
votes
2answers
175 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 ...
3
votes
1answer
169 views

How to determine USB hub speed type?

I'm developing a driver for multiple USB speeds and according to the universal specification, I'm allowed to draw a greater amount of current from a USB 3.0 hub than the other versions. Is there a ...
3
votes
3answers
200 views

5V Across Multiple USB Ports

I've got a board I'm working on that I think may have two USB ports and both of them could conceivably be connected to a computer at the same time. Both USB connectors need not be connected to the PC, ...
8
votes
5answers
7k views

Can an Android tablet serve as USB Host and be charged simultaneously through a single port?

A number of Android tablets are powered through the Micro B USB port but also provide USB Host support through the same port (e.g. Motorola Xoom 2, Acer A510/700). I need to be able to use USB Host ...
1
vote
1answer
793 views

Power Kinect from laptop (or another mobile power source)

First of all, I'm passionate about electronics, but that's just like a football fan saying he's passionate about the sport but can't actually play. I'm a programmer, so since I'm on the tech side I ...
7
votes
3answers
793 views

USB bus powered hub - more than 100 mA per device?

I'd like to ask a quite specific question regarding the USB power management. First of all, I will outline the design of my device. It is a symmetric signal line driver with a builtin audio codec for ...
2
votes
1answer
488 views

iPad Doc connector: is it possible to using the camera connection kit while charging the ipad

I'm building a touch screen kiosk using an iPad and a USB BarCode Scanner (through the camera connection kit). the problem: The pinout here shows the USB pin that the scanner would connect to. ...
2
votes
4answers
3k views

Could HDMI be potentially used as a power supply alternative for smartphones?

I understand that HDMI's pin 18 carries a +5V charge. Similarly, USB carries 5 volts and this is used to charge many smartphones with a micro/usb connector. Could it possible to build a smartphone ...
2
votes
2answers
331 views

What would I need to open a circuit (a usb cable) for a few seconds, on a given time?

I have a USB cable connected to a USB modem. On a specific time of day (say, at midnight - but it should be configurable) I would like to open the circuit for a few seconds. The result should be ...
4
votes
3answers
288 views

Sensing when micro USB power cable is unplugged from a smartphone (or other device)

I am looking to create a charging device that can provide 5v power to charge a smartphone (or other consumer electronics device) via micro USB. How would I go about making this charging device "aware" ...
3
votes
2answers
2k views

Switch between battery and USB power

Following on an earlier question I am looking for a circuit where it powers from USB when it is available and uses the battery when USB is not plugged in. I want voltage drop to be minimal, zero if ...
1
vote
2answers
636 views

What if I try to connect a 12V@0.16A computer case fan to my USB port?

What happens if I try to connect a 12V@0.16A computer case fan to my USB port? Purchased a USB laptop HDD enclosure lately but it coming with no fans. So I thinking of putting fans around enclosure ...
3
votes
1answer
832 views

a strand of usb cable is yellow not black

I cut the wire of a USB keyboard to supply 5V power to my Arduino. I expected to find Red wire for +5V, Black for GND, White for D-, and Green for D+. However, there is no Black, instead, there is a ...
5
votes
1answer
1k views

Arduino Duemilanove external power source with USB connected

Can Duemilanove USB interface be used for data transfer/programming when the board itself is connected to an external power source? (say, USB is not powerful enough) What are the requirements for the ...
3
votes
3answers
592 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 ...
2
votes
2answers
364 views

Netduino powerd by USB wall charger

I have a IPhone wall charger. Can I plug my netduino into it to power it via USB?
1
vote
3answers
832 views

USB without Vcc

I want to remove the Vcc pin from a USB cable and connect my computer to a device. My goal is to allow the device to communicate with the computer while not charging the device. Does some section of ...
3
votes
4answers
350 views

Male Apple Dock Connector => USB (power only)

I have an old external battery for Apple devices (has 30 pin Apple Dock Connector), and I want to repurpose it to be an external battery for all my USB devices. Anyway, I don't have much experience ...