Smartiepart EL backlight noise

flashbang · Post by **flashbang** » Sat May 05, 2012 12:39 pm

Running the SP board and the EL backlight on ER9x 760. While a excellent product I notice a annoying fluctuation of digits on the trim increment info screen when the BL is on. I believe this EL BL uses quite a bit more current than the HK LED BL and digits "dance" with the light on. Anyone else notice this and is there a fix?
TIA

Post by **Crucial** » Sat May 05, 2012 12:42 pm

I've known about this for some time but just ignored it. It hasn't caused me any trouble while in flight so far.

Post by **Crucial** » Sat May 05, 2012 7:41 pm

Quick video of the effect I see. Is this similar to what you see?

http://www.youtube.com/watch?v=ifVxhbED ... ature=plcp

flashbang · Post by **flashbang** » Sat May 05, 2012 8:07 pm

Yes, plus the jitter is also on the screen in the pic on my first post. Quite annoying but harmless unless you actually want to see the values with the light on.

Post by **ShowMaster** » Sun May 06, 2012 2:22 am

Just to narrow it down.
Does this happen when the EL panel is disconnected?
Several conditions to sort out. If it happens with the EL panel disconnected it could be the EL driver circuit proximity to the CPU board, or HF AC getting into the power rail and into the CPU power rail. That would be one condition and fix required.
If it happens when the EL panel is powered it could still be the driver circuit now that it's loaded or the proximity of the powered El panel being sandwiched to the back of the LCD display and coupling AC/RF into the display or it's power source.
I myself use the SP board but have chosen to use the HK white BL. I still have the SP EL circuit active, just without the EL panel. To date I don't believe I have any display issues mentioned with this setup.
Since you're having it possibly you could isolate it more to the EL circuit or panel.
Thank you
SM

flashbang · Post by **flashbang** » Mon May 07, 2012 1:34 pm

What I have found is with the EL unpluged and the SP board in the jitter stops with the light switched on or off. With the board out same results. Seems that the draw from the EL light causes the issue.

Post by **ShowMaster** » Mon May 07, 2012 2:23 pm

It may be the fact that the el panel is being driven with high voltage AC and the AC is capacitive coupling into the display.
That being said I'm not sure of a fix for that. Fortunately you could convert to the HK led backlight and still take advantage of the SP boards ease of instalation. In my case I use SP without the EL BL but take advantage of the solder pads on the SP board for the telemetry and BL led control. I avoid having to solder to the CPU pins but for telemetry I do have to reroute the 2 required pins but that has to be done in any case.
The SP board has been selling for over a year and either most don't notice any el interaction or ignore it? Steven has redesigned the board a few times, maybe it's not in all model?
Being that the BL is not on that much and it only causes a small digit flicker and you've tracker it down, is it somethig you can be OK with?
I'm sure if there is an easy fix someone will post it soon now that it's know about.
A fellow flyer just got his SP board and is installing it. I'll take a close look at his when we get together to fly.
SM

flashbang · Post by **flashbang** » Mon May 07, 2012 3:06 pm

I can deal with it as it is not a major issue, just a nuisance that I found out after buying the board. I would still by the board as I think it is a great idea, but if there is a fix I will apply it. Interesting to know that you can use the board for the HK BL mod. Any info on how to perform this?
TIA

Post by **ShowMaster** » Mon May 07, 2012 11:13 pm

Pin 17 on the CPU is also the VDD pad on the SP board. VDD/pin 17 is the pin the er9x firmware toggles from 0 to +5v. This connection should go to the HK backlight and the gate of the added FET for light on off control. The HK backlight and FET mod is well documented with how to's and pictures but I'll have to look for them or you can do a search.
If you decide to do it I'm sure you'll get all the advice you need so just ask.
SM

gohsthb · Post by **gohsthb** » Mon May 07, 2012 11:45 pm

The atmega64 runs on 5V. The pin should output either 0 or 5V.
-Gohst

Post by **ShowMaster** » Tue May 08, 2012 12:31 am

gohsthb wrote:The atmega64 runs on 5V. The pin should output either 0 or 5V.
-Gohst

Thanks I corrected my post to read 0 - 5V. Too many boards and processors in my head.
SM

Post by **MikeB** » Tue May 08, 2012 10:22 am

You think you've got trouble with too many boards etc.

Mike.

Post by **ShowMaster** » Tue May 08, 2012 12:05 pm

Mike, save room in your for the rumored HK and Frsky TXs.
You right, I'm overloaded with 2.
SM

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