The SheevaPlug is reputed to have a marginal power supply. It seems to be more of an issue for the people in the UK running at 240VAC, and it also seems to be a problem to load the USB too heavily, as happens if you want to add an external mechanical disk drive. Add to that, the fact that I live in a part of the world where the power is pretty unr
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eliable in the winter. Storms knock down trees and they take the power lines with them. This project attempts to kill three birds with one stone: The premise of the circuit is simple. The SheevaPlug, USB hub, and laptop hard drive are all designed to operate on 5VDC. The circuit utilizes a DC-DC converter to provide +5VDC for the whole system. The DC-DC converter is designed to take input power in the range of 11-24VDC and convert it to a constant 5VDC output. The only bit of trickiness is to arrange for two separate sources of power to feed the DC-DC converter. The main source comes from 120VAC house wiring through a standard laptop power adaptor. The backup source is from a 12V lead-acid battery. The laptop charger was chosen for easy availability, efficiency, small physical size, and a voltage output of at least 18 VDC. I got a replacement charger for an HP Mini 1000/1100 netbook. It is a 30W adaptor that puts out 19VDC at 1. 6A. It uses a 4. 0mm connector with a 1. 7mm center post, where GND is on the barrel, and V+ is on the center pin. I got a replacement HP Mini 1000 adaptor on eBay for under $10, shipping included. The battery backup power arrives in the form of 12VDC from a lead-acid battery. Even with a charger attached, the voltage across the battery is less than 18 VDC. I will be using a high-quality charger that does not overcharge the battery. In practical terms, this means that you can leave the battery on...
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.....
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