I am creating a custom fileserver from an old case and parts. The mod involves cutting an old case down to about half-height, adding a white plexiglass shell to the chassis, and making it all really quiet. I am modding an 8-port network switch into the case and I will have room for eight hard drives. So basically I am looking at having at least 20 indicator LEDs on the front of the case, 8 of which are dual color from the network switch. I have a handfull of BC337 NPN transistors and I would like to implement them in an LED indicator blackout feature. How do I do this? Do I need to put a resistor on the emitter of each transistor? Any repercussions in the emitter being hooked back into the network switch's board? Do any of these questions make me sound like I know what I am talking about? Please advise!
I take it all these LEDs have the cathode switched? If so, then just hook up 3.3v or 5v (whatever the switch or device uses in the first place, but you can get a line from the power supply) and a resistor to each LED, and just switch the power on and off with a switch. If the LEDs are bidirectional dual color, (2 leads) then thats a bit more trouble, but most likely they are 3 lead tricolor (one color, the other, or both) or even 2 separate SMD LEDS right next to each other on the board. Basically 1) remove old LEDs 2) identify which line is switched 3) find out which side of the LED the resistor is on 4) find out what voltage the switch feeds to the LEDs If, the cathode is switched, the resistors are on the cathode too, and is uses 3.3 or 5V, then all you need is a single switch, some new LEDs and some wiring. If the resistor is on the anodes, you will need some resistors too.
I am not sure if the cathodes or the anodes are switched on the device. Are you referring to a transistor when you said "switch" the third time? I am pretty sure I need the transistors so they will keep the different indicator signals separate while I control them all with only one toggle switch. I am sorry, they are three lead tri-color (didn't count the fact that both could run at once). The reason I think I have to hook the emitter straight back into the network switch is because the trans has to be after the load (LED) for the trans to act as a switch and not a "variable resistor." How far off am I here?
Most likely the positive side is going to be switched for the LEDs. To find out which side is positive, get a multimeter, and while the led is on, hold the tips of the multimeter to the leads of the LED. If the multimeter reads positive, than the RED lead on the multimeter is the anode (positive) lead on the LED. If the multimeter reads a negative number, than the BLACK lead on the multimeter is the anode (positive) on the LED. If i were to make my own circuit, i would now tie the cathodes (negative) leads on the LEDs together, and throw a switch between all the cathodes and the ground on the PSU. Then on the anodes, put the correct resistor for each between the switching source for it. I dont know exactly what to do with your switch, but if the negative side is switched, then tie the anodes together. Just make sure that no mater what the final circuit looks something like this: Code: -----------(/)------/\/\/\-----------\ (LED) (R) ------------------/ ------------ -----------(/)------/\/\/\-----------/ (switch)
