The USB standard restricts the current consumption of all USB devices to either 100mA or 500mA depending on the specifics of the USB hub and/or host controller (i. e. computer) that is supplying the power. Ideally, no USB device should ever pull more than 500mA of current from a USB port. In reality this is not always the case. There are two main
Click here to download the full size of the above Circuit.
issues that can cause a USB device to attempt to exceed the 100mA or 500mA limit. The first is high "inrush" current during the startup of some USB devices. For example, a USB hard drive trying to spin up can temporarily attempt to pull much more than 500mA from its USB port. The second issue is the connection of high-power USB devices through long USB cables or active USB "repeaters" (really really long USB cables. ) In both cases, the large voltage drop that can occur over the length of such USB cables will cause some USB devices to be under-powered and fail to work reliably. or at all. Lastly, some USB host controllers are notorious for being "weak" and unable to provide the full power required by the USB standard. Weak host controllers are found in some laptops and peripherals with integrated USB hubs (such as computer monitors, printers, etc. ) USB POW is also ideal for allowing high-powered USB devices to work reliably with under-powered host controllers and hubs. Below are the schematics for USB POW. The latest schematic is revision 1. 3. Older schematics are also shown, but only for historical information. They are not guaranteed to work correctly. The printed circuit board for USB POW is a standard 2-layer board. Board revision 1. 3 allows USB POW to be used with DC power supplies whose polarity is tip = positive, ring = negative. Board revision relies on the less common polarity tip = negative, ring = positive for...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: