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Old 05 April 2010, 10:01   #1
Calgor
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Disk activity LED for Acard SCSI-IDE adapter

I would like to have an LED showing the disk activity for the storage device attached for my Acard 7720U SCSI-IDE adapter inside my A1200 desktop case.

This adapter has 2 pins on it for connecting such an LED, but I am not sure of how much voltage drop is across the 2 pins, and also the specs of the LED required (and if any resistors also needed in series)

Has anyone done such a thing?
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Old 05 April 2010, 10:22   #2
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Usually if things have a led output, all you need to do is connect a led, nothing more. Any old led will be fine.
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Old 05 April 2010, 10:56   #3
Calgor
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Seems most normal LEDs (unless blue or white) need voltage of 2V and no more than say 3V (for example). And not supposed to connect directly to power supply else will burn out.

Here is a good webpage:
http://www.kpsec.freeuk.com/components/led.htm

@ Loedown

Yes I would imagine so, but I do not like to assume where irreplaceable amiga hardware is concerned. There are a few pieces of hardware with gotchas and mislabelled silkscreens where pin 1 is for example.

The Acard doco says it is jumper JP3 but does not say which pin is positive voltage (or what the voltage is).... does anyone know?
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Old 05 April 2010, 11:24   #4
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Hi Calgor,
This is probably going to be a mod I'll do with my A-Card when I finally get round to plumbing it in.

While you are of course taking a responsible view you'd be amazingly unlucky not to get away with the butcher's route:
-Hook it all up.
-Sacrificial LED in hand, start a file-transfer.
-Touch the pins the way round you suspect it may go.

It works? You were right
It doesn't? Never mind, try the other way round...

As you probably know an LED is a diode so the wrong way round it just won't work - no worries.
I'd be very surprised if PCB LED pins would supply too much current / voltage but your sacrificial LED won't be connected long enough to burn out & it's brightness will give you a clue regarding:
-Do I need a series resistor? (surprisingly too much voltage - v. bright)
-Will I need to go looking for a low voltage LED? (dim - not likely)

Interestingly my 'A-Card' doesn't have a spot for an LED, so I'll have to connect an activity LED direct to the IDE connector - That DOES need a series resistor.

Regards,
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Old 05 April 2010, 12:42   #5
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I have many times used the LED output in HDs with just the LED connected.
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Old 05 April 2010, 13:05   #6
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Well it seems the worst that will happen will be the LED will get burned out. Thanks for the tips all. Will let you know how it goes.

The following website says that at least for hard disk LEDs on normal PC motherboards, the voltage on the LED header is of no consequence as the motherboard will limit the current. The voltage would vary depending on if you had a higher voltage blue LED or lower voltage red LED:

http://case-mods.linear1.org/hdd-header-hints/
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Old 05 April 2010, 20:39   #7
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HD LED connector always have a in-series resistor to attach a LED directly on the header.
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Old 05 April 2010, 20:49   #8
mfilos
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Interesting thread as I needed to do the same to my ACard as well :P
My only concern was the following:
- A1200's IDE port is what the mobo LED header is showing on access/write times.
- ACard's LED header is showing whatever attached to the ACard.

Do I need to put some extra resistor or anything else in A1200's LED panel in order for me to be able to include both Internal's IDE+ACards led output?
I wanted to have in same LED (the normal one) both Interfaces
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Old 05 April 2010, 21:02   #9
prowler
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Quote:
Originally Posted by mfilos View Post
Do I need to put some extra resistor or anything else in A1200's LED panel in order for me to be able to include both Internal's IDE+ACards led output?
I wanted to have in same LED (the normal one) both Interfaces
No resistor necessary. Just a couple of signal diodes (1N4148), one in each led output line.
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Old 05 April 2010, 21:10   #10
mfilos
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Thanks Prowler. I'll try that out
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Old 25 January 2012, 08:30   #11
Bamiga2002
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Can I connect the LED header of my D-Box tower to my ACard led-connector and it will work?
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Old 25 January 2012, 09:38   #12
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Yes.
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Old 25 January 2012, 10:34   #13
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Ok
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