Simple USB Power Injector For External Hard Drives

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A portable USB hard drive is a great way to back up data but what if your USB ports are unable to supply enough to power the drive? As with most such drives, it is powered directly from the USB port, so it doesn’t require an external plugpack supply.

In fact, the device is powered from two USB ports, since one port is incapable of supplying sufficient current. In use, the two connectors are plugged into adjacent USB ports, so that power for the drive is simultaneously sourced from both ports.
An external USB hard drive is usually powered by plugging two connectors at one end of a special USB cable into adjacent USB ports on the computer. Although the USB drive worked fine with several work computers, it was a “no-go” on my home machine.

circuit diagram :

Source: Silicon Chip 26 June 2008


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This is very Simple way to modification standart usb converter to OTG USB.
The most Mini or Micro USB to USB converters are not work if you want to use it for OTG converter, because the 4. pin of the micro usb plug is not connected.

This below is an original cable schematic :

If you want to use it for working OTG adapter you have to connect the micro usb connector 4. pin to GND (5. pin).

Like this below :

This schematic is working me. Let to try this stuff.

Original document USB OTG mechanical

USB RS232 Converter

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USB – RS232 converter, uses only Tx and Rx lines, with selectable 2400, 9600, or 38400bps. PCB projected to fit in old mobilephone cable, most of parts is surface-mounted. For more info see original autor Osamu Tamura site. Pcb’s, driver, and firmware is attached below.

download rs232_usb pcb, schematic, driver, firmware


Very Simple VGA schematic

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A simple VGA interface can be built on a breadboard with some resistors and a connector. The red, green and blue VGA signals are each driven by a simple DAC like the one shown below. Each color input presents a 75-ohm load to the DAC. The DAC resistors combine with the load resistor to divide the 3.3V digital logic outputs so the total stays below the maximum 0.7V expected by the VGA input VIA

This prototyped a 512-color VGA interface board which worked just fine, but he thought it would be way too cumbersome to use for each and every project. To keep life simple, he designed a small PCB that integrates a VGA connector and all of the resistors he needed to get the signal from the FPGA. His boards plug directly into a breadboard, so only a handful of wires is needed to connect the FPGA to a monitor.

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