![]() ![]() The transistor can be generic, cheap 10-20 cents one, just must be able to turn on at less than 5v and be able to let the led strip's current pass through (200mA to something more) So when the led is supposed to turn on, there's energy sent into the base of the transistor, which creates a connection between the and so the of the led strip is connected to the ground of the motherboard (the - of the hdd activity led) collector of transistor connected to the of led strip and the of the led strip connected to +12v or whatever voltage the led strip needs. from hdd activity led -> emitter of transistor from hdd activity led -> resistor (for safety, protect mb and transistor, etc) something like 1 ohm (low value, because current is already small enough) -> base pin of transistor If you want to connect a led strip or something which would be powered from 12v or some other voltage (so basically you don't want the leds to be powered by the motherboard), then you would use a npn transistor or a mosfet to act like a switch, which would basically turn on or off the power going to a separate strip of leds.įor example, let's say yo want a led strip to flicker based on hdd activity. Modern efficient leds will still light up substantially at 1mA or even less ( the high brightness red leds with small angle lens on top are very bright even at half a mA) 2 leds = half the original current, 3 leds = each gets a third. So you can put additional leds in parallel with that led, but then each led will receive less current. ![]() The modern green and blue leds are very power efficient so that limited amount of current is good enough, they'll be quite bright even with just that little current. The pins on the motherboard provide a limited amount of current, maybe about 5mA, and it's usually powered from 5v stand by. In fact, on my custom-built desktop, there is a disk activity light on the motherboard itself so one could see if the disk(s) are busy (assuming a windowed case) even if the PC is on a table and the case's own disk activity light isn't as readily visible.The HDD activity and power on LEDs are in that header where you put the power on and reset wires coming from the case. A computer in normal operation will have intermittent disk accesses if the system stops responding and there is no disk activity whatsoever for several minutes, chances are very good it needs to be forcibly rebooted. ![]() A more comprehensive way to monitor disk activity is to use Task Manager, which as of Windows 8 can show disk activity.Įven so, the light is still of use to determine if the system is loading data from disk or is completely hung. In fact, many newer PCs, especially thin-and-light laptops, omit the light altogether. This still holds true for modern PCs that are configured to boot and run applications from a electromechanical hard drive, but with the increasingly widespread use of solid-state drives which can access data in a matter of microseconds rather than milliseconds, the amount of time the system spends waiting for disk is far less, and the disk activity light is of less value on systems with SSDs. If the system seemed stuck but the disk activity light was on, chances were good that the system was just waiting for the disk rather than actually hung. Before the advent of solid-state drives, long load times for the OS and applications were the norm, and while one could hear the hard disk seeking, the light was a much more reliable indicator of disk activity since sequential I/O is not noticeably noisier than disk idle. The main purpose of the light is to allow the user to determine if the system is busy due to disk activity. Shown here is an IBM 350 disk unit used with the IBM 305 RAMAC computer, which dates back to the 1950s. The disk stacks themselves on those drives were designed to be physically interchangeable. The disk activity light looks like a cylinder because early hard disk drives for mainframes consisted of large cylinders of platters and corresponding sets of read/write heads. ![]()
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