Sharing one "activity" LED for two HDDs (Mega STE)

[Pacman]

I've got a Mega STe with both an internal SCSI hard drive and a CF-IDE adapter (attached to a MonSTer board).
Would it be possible to have a single LED (as the factory installed one in the front of the hard disk section of the case) for both drives without too much hassle?
I'm thinking an LED with 3 legs (two coloured I believe) or one that I found in my parts box with two legs but emits different colours according to the polarity power is applied.

The SCSI drive will mostly be disconnected (i.e. its power connector disconnected) as I have the CF-IDE now and it'll keep down noise and heat, but I suppose with its data connector attached the GND pin of its LED will be common with GND from the MonSTer's LED pin, but I haven't checked to confirm this.

[stephen_usher]

You could potentially add a diode on each line so that one drive doesn't try to power the other, but this will introduce a voltage drop and hence dimmer LED when just one drive is being accessed.

[Pacman]

You could potentially add a diode on each line so that one drive doesn't try to power the other, but this will introduce a voltage drop and hence dimmer LED when just one drive is being accessed.

I'd rather not have that.
How about that bi-polar LED I found which lights green, and when the polarity is reversed it's red? Could that somehow be connected to the two drives.

UPDATE: I realize it's been a while since I last bought LEDs as I just found out this is available::

4pinled.jpg (40.05 KiB) Viewed 4033 times

(image source: MPJA electronics)

I could get one of those (which would fit into the same location as before in the MSTE), and assuming both drives' LEDs share the same GND I connect one of them to the LED and have two of the LED's + pins go to each drive.

But if I could use the bi-polar LED I already have I don't have to wait for a new order to arrive

UPDATE: I just checked the MSTE SCSI hard drive while attached and the cathode doesn't go to a common GND as expected
But given I use an LED with multiple legs, would it still be OK to connect both drives' minus pin to the LED's common cathode, and use a dedicated cathode pin for each drive?
I would still like to find a way to use my bi-polar LED if possible though.

[Pacman]

Having asked around for solutions to this several places and seeing it's going to be complicated I'm starting to look into using two separate LEDs instead: one for each drive (SCSI HDD and MonSTer-attached CF card). There's a 3mm LED in the MSTE hard drive bay mounted on a metal lug with a hole that fits a rubber grommet.
Finding a way to mount two LEDs side by side would be non-reversible as I'd have to cut in the metal, so I'd like to hear opinions on this before proceeding. The biggest question is if both LEDs will light up adequately or not. LED size and shape could affect this (I have both flat and round ones to choose from).

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20210418-175317_P4180027.jpg (154.04 KiB) Viewed 3933 times

[stephen_usher]

A 3mm dual colour LED would do what you want. They have three leads, one for the each colour and a return. Simple enough to wire.

Remove the remains of that original PVC gromet, clean the steel up, paint the area so it doesn't rush any further and fit a 3mm PVC gromet (6mm external) into which you can press the LED.

[pixelpusher]

Having asked around for solutions to this several places and seeing it's going to be complicated I'm starting to look into using two separate LEDs instead: one for each drive (SCSI HDD and MonSTer-attached CF card). There's a 3mm LED in the MSTE hard drive bay mounted on a metal lug with a hole that fits a rubber grommet.

Just as a curious note: These metal holders (with the rock hard rubber) seem to be prone to corosion in any machine I've seen so far. Wonder what causes it (as I wouldn't expect a lot of fluid or corrosive content there)...

[frank.lukas]

It´s not a PVC gromet but a silicone gromet with containing vinegar ...

[stephen_usher]

Actually they were PVC which, if it disassociates, releases hydrochloric acid.

[Pacman]

A 3mm dual colour LED would do what you want. They have three leads, one for the each colour and a return. Simple enough to wire.

Remove the remains of that original PVC gromet, clean the steel up, paint the area so it doesn't rush any further and fit a 3mm PVC gromet (6mm external) into which you can press the LED.

Yes, this was my initial idea until I found out that the negative LED terminal of the internal SCSI drive isn't the same as the GND terminal of the power supply (I assume common GND is used for the MonSTer drive activity LEDs, but for the moment it's not installed because of some issues with it so I can't check to verify).

[Pacman]

Remove the remains of that original PVC gromet, clean the steel up, paint the area so it doesn't rush any further and fit a 3mm PVC gromet (6mm external) into which you can press the LED.

Good idea to clean up the steel.
I thought it was strange to see all the rust there when there was none on the rest of the HDD mounting frame, but this thread explains it. May I ask what causes PVC to release hydrochloric acid? Are there any other grommets of a different material which may be better suited?
I believe I found a suitable grommet with those measurements from RS components:

3mmgrommet_rs.png (631.89 KiB) Viewed 3845 times

It would be great to simply fit a dual coloured 3mm LED in there as you suggested, but without a common GND between the two drives' LEDs I'm considering putting a 3mm LED back in using the rubber grommet/mounting frame, and placing the other one right next to the transparent diffuser. If I'm lucky that LED will light up sufficiently as well due to the diffusion and angle.