Raptor Computing Systems Community Forums (BETA)

Raptor Computing Systems Hardware => Blackbird => Topic started by: FlyingBlackbird on February 11, 2020, 03:52:36 pm

Title: How to connect HDD activity LED?
Post by: FlyingBlackbird on February 11, 2020, 03:52:36 pm

The User Guide for Blackbird explains on pages 18 + 19 the J9800 Front Panel pins to connect eg. LEDs like HDD activity, Power LED and NIC LEDs:

https://wiki.raptorcs.com/w/images/c/ce/C1P9S01_users_guide_version_1_0.pdf

What is unclear to me is how I can connect a usual two-pin HDD LED plug with the front panel pins since

- I can see only one Pin (#14) for the "HDD activity LED cathode" but
- no obvious PIN for the HDD activity LED anode.

So the two-pin HDD LED plug from my case has no obvious two neighbored pins to be plugged into.

1. Which front panel pin should be used for the anode of the LED?
2. Which cable could I use to split the two-pin HDD LED plug from my case into two separate pins for a reliable connection?

Title: Re: How to connect HDD activity LED?
Post by: MPC7500 on February 12, 2020, 08:10:10 am

I would try "13 Identify button (active low)" for anode. Haven't tried myself.

Title: Re: How to connect HDD activity LED?
Post by: xilinder on February 12, 2020, 09:21:05 am

You could use (I did) something like this with a 150 Ohm resistor inline on one of the legs and connect to pins 14 and 15.

https://www.sparkfun.com/products/9140

and use some shrink tubing to insulate.

Title: Re: How to connect HDD activity LED?
Post by: FlyingBlackbird on February 12, 2020, 04:11:27 pm

Quote from: xilinder on February 12, 2020, 09:21:05 am

You could use (I did) something like this with a 150 Ohm resistor inline on one of the legs and connect to pins 14 and 15.

https://www.sparkfun.com/products/9140

and use some shrink tubing to insulate.

Shrink tubing is a good idea, I already have thought about using my Rapsberry Pi jumper cables...

Why do I need the 150 Ohm resistor for Pin 15, is 3.3 V too much?

Title: Re: How to connect HDD activity LED?
Post by: xilinder on February 13, 2020, 08:31:24 am

That depends on the LED. If you are using a 3.3v LED then you should not need one.
Most of the older LEDs can only handle maybe 20mA and if connected to 3.3v power source will 'blowout' so fast it will not be noticeable.

So.....you must know the max voltage and amperage of the LED for proper operation.

For example, if the LED turns on at 0.7v and can only handle 20mA and you are suppling 3.3v then..3.3v - 0.7v = 2.6v. 2.6v/.020A=130ohms so a 150ohm reststor will allow the LED to last a long time.

If the on-board LED driver chip limits the Amps then the resistor should not be required. I would assume this is the case with the Blackbird.