Sky9x Board - LED Light

Post by **Rob Thomson** » Tue Jun 26, 2012 3:13 pm

Right...

I am 99% certain this has already been posted somewhere! But as I could not find it I will ask the question in a new thread!

The WIKI docs for the sky9x board indicate that a resistor should be clipped if using the stock board. However no mention or image is provided as to where exactly this is?

Brent.. can you let me know on this thread, then I will copy the image to the wiki for you?

Rob

SkyNorth · Post by **SkyNorth** » Tue Jun 26, 2012 3:37 pm

To Use the HK backlight , you need to clip off or de-solder the small round 68 Ohm resistor on the Switch side of the board.

The other option is to use 150 Ohm resistor is series with the backlight connector , and leave the 68Ohm resistor in place.

-Brent

kaos · Post by **kaos** » Tue Jun 26, 2012 3:47 pm

that's a new invention for sky9x board, it makes a piece of foam to glow.
just make sure the 150 ohm resistor is on the + wire.

good pic, my board still somewhere between canada and US.

Post by **Rob Thomson** » Tue Jun 26, 2012 4:00 pm

Thanks. All done on my board.

Just the wiki to update

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Hexperience · Post by **Hexperience** » Tue Jun 26, 2012 9:34 pm

Brent, was this required on the early beta boards as well? I just plugged in the HK backlight with no changes.... do I have a ticking time bomb in my hands?

SkyNorth · Post by **SkyNorth** » Tue Jun 26, 2012 9:46 pm

I do not have a HK backlight , so the resistor values I used came from SM.

The beta Board has a 100hms built in and a 100ohm soldered in, to give 50 ohms.

I take it you have the intensity level set low , this should be fine , as the average current is below the maximum current rating.

You could add a 150 Ohm to lower the total current , but you will have to turn up the intensity to get the same brightness level back

-Brent

Post by **ShowMaster** » Tue Jun 26, 2012 9:50 pm

The series LEDs draw 15 Ma, 20 max. Measure the current drawn to see if your OK.
SM
2 LEDs in series @15 MA from a 5 volt source = 200 Ohms total series resistance

SkyNorth · Post by **SkyNorth** » Tue Jun 26, 2012 11:40 pm

Since the Backlight is driven by a PWM , it gets "Pulses" of 5V power to it .

By dimming the Backlight these pulses are narrowed , so much that the Average current is below the 20mA max , But each
pulse is actually greater than 20mA .

Unless you have a true RMS - DVM good to 10khz , its hard to get a real accurate current reading.

All said , adding a 100 - 200 ohm resistor , would not hurt.
-Brent

Post by **ShowMaster** » Wed Jun 27, 2012 12:21 am

At the full brightness level how close to a 100% would that be I wonder?
The higher resistor value (200 ohm) may still be valid since the LEDs will be close to 5 volts.
SM

Hexperience · Post by **Hexperience** » Wed Jun 27, 2012 10:05 am

I have the brightness set at 8. I only wanted it bright enough so I can see it in the shade. I was checking the current on the status screen and with the backlight at 8 I'm seeing about 130. (I'm assuming that's milliamps)

Post by **ShowMaster** » Wed Jun 27, 2012 2:33 pm

Hexperience wrote:I have the brightness set at 8. I only wanted it bright enough so I can see it in the shade. I was checking the current on the status screen and with the backlight at 8 I'm seeing about 130. (I'm assuming that's milliamps)

The status screen should be showing total tx current draw , sky board, tx module and backlight. The 130 should change when the backlight is off. What is that value? The differance is the BL.
It's my opinion that if your board had the SMD 100 ohm resistor paralleled with the 100 omh on the board backside this 50 ohm total is too low to limit current to a safe value when set to full brightness value. Adding another 100-150 ohms in series will make sure the LEDs don't draw excessive currant. This protects them and the regulator from drawing excessive currant.
I may not be 100% correct on this theory wise but I want to be on the safe side.
Hopefully someone with a true rms current meter will measure the current values for differant settings and series resistors.
SM

Hexperience · Post by **Hexperience** » Wed Jun 27, 2012 9:10 pm

When I turn off the BL it drops by about 10. I have an optrex display coming in a day or two...

It was the easiest solution to the problem..

manu · Post by **manu** » Sun Jul 01, 2012 3:11 pm

SkyNorth wrote:To Use the HK backlight , you need to clip off or de-solder the small round 68 Ohm resistor on the Switch side of the board.
68OhmResistor.JPG
The other option is to use 150 Ohm resistor is series with the backlight connector , and leave the 68Ohm resistor in place.
150OhmResistor.JPG
-Brent

Is there a description/part#/link of that specific plug I need to connect the HK LED BL?
EDIT: Aaah, there is one in the plastic bag of the rotary encoder!
regards
manu

SkyNorth · Post by **SkyNorth** » Sun Jul 01, 2012 3:29 pm

Digi-Key
JST - "PH" series
Housing - 455-1165-ND
Contacts - 455-2148-1-ND

kaos · Post by **kaos** » Sun Jul 01, 2012 4:45 pm

where can I find the best link to all the sky9x board connections.... etc. My board came in with spker and encoder , no instruction /diagram.

Post by **Rob Thomson** » Sun Jul 01, 2012 5:01 pm

Check the hardware mods ion the wiki.

There is a section for the sky9x board.

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kaos · Post by **kaos** » Sun Jul 01, 2012 6:30 pm

Thx. I will.

kaos · Post by **kaos** » Mon Jul 02, 2012 3:52 am

I think there is a typo on the diagram "main board connections" in wiki, it should be 'FrSky' connection, not 'FlySky' connection.

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