Most PC enclosures provide only a single LED to indicate hard disk access, with the LED being connected to the motherboard via a two-pin connector. However, this LED only works with IDE drives, and if a SCSI disk controller is fitted, its activity will not be visibly noticeable. This small circuit remedies that problem using a multicolour LED. The
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activity LED for the IDE interface is usually driven by a connected device via one or more open-collector stages. It illuminates if either of the two possible IDE drives is activated. The shared series resistor limits the current and also provides short-circuit protection. Even if the LED is shorted out due to faulty wiring, the current is restricted to a safe level. An obvious solution would be to have the IDE and SCSI disks drive a shared dual LED, but unfortunately the current flows from the positive supply line through a series resistor, the LED and a transistor to ground. The dual LED would thus have to have a common anode, but no such device exists. All known multicolor LEDs have a common cathode lead. That means they cannot be connected directly, but we`re not that easily defeated. Only a small additional circuit is needed to allow the LED to be driven by the different interfaces. In this circuit, each of the drive signals from the two controllers is fed to an optocoupler, which acts nearly the same as the original LED. The somewhat lower voltage drop of the infrared LED results in a somewhat greater current, but there`s hardly any need to worry about overloading. The optocouplers eliminate the problems with the different voltages. On the output side, a Darlington transistor consisting of the photo-transistor and a BC547 drives the multicolour LED. The 10-k resistor (whose value of is not critical) provides secure...
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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