Electronics LED Relay Question?

Hi, i want to take my hdd LED and put a relay on it so that when the hdd light is activated the relay will switch, the switch will then activate 4 LED's (causing 4 time the amount of light) my question is what relay would/should i use (please quote part codes etc from maplin) - if this isnt the best way to do this please say why and what is.

Thanks
N4N01D

 

What if you was to change the single led, into a series of leds. that might work. or if you just want brighter light buy a single hyper bright led, and swap it around.

check here for leds, www.ultraleds.co.uk.

hope thats some help.

 

na if you connect them in series the power drops and isnt enough to power them @ the same brightness, hence my need for a relay for a parallel setup, and i need about 4 led's

 

Series LEDs wouldn't work, and using a relay is just plain overkill. What you're looking for is an optoisolator. An optoisolator is basically a small chip with an IR LED and a transistor in it. Put the HD signal straight to the opto's LED pins, and whenever the HD signal is active, the LED inside the opto will light, which will cause the transistor to conduct. Here's a quick schematic I did in notepad

Code:

HD + - - - - - -|  /|- - - - - - - - +5v
                | | |
HD - - - - - - -|  \|-v^v^v- - - -
                           | | | |
                           - - - -
                           V V V V
                           - - - -
                           | | | |
                           - - - - - - - - GND

 

The HDD Activity switch doesn't have the power to run a relay, best n00b way is to swap the single HDD led for the led in an optoisolator (4N25) and use that to switch a transistor (2N2222) that can run a few leds with no risk to the mobo.



Your leds & resistors go where it says 'load'. Will work OK on 5V, just use a suitable LED resistor.

edit: whypick1 beats me...

 

Additionally it may be sensible to add a diode in series with the IR LED, as the typical forward voltage of an IR LED is only 1.2V.

 

ok thanks, off to maplins then soon

 

I take your point, but the mobo usually limits a 2V HDD led's current to under 10mA, so a 1.2V led still only gets about 14mA.

 

Check here for some extra info

http://forums.bit-tech.net/showpost.php?p=88069&postcount=5

I found it helpful. Knowing extra doesnt hurt.

 

Yep, that's the way to go. For just a few LED's, i wouldn't use an extra transistor, the phototransistor should handle that sort of current.

 

Google 'optoisolator current transfer ratio'.

A good darlington one might just run 3 leds, an external transistor will run 20+ at full brightness.