Backlight - EL vs LED

Post by **erazz** » Mon Feb 27, 2012 3:43 am

Hotly debated topic. Let's make it hotter....

I've just installed the Led BL from HK on my spare TX. I am appalled!

Being thicker it's slightly harder to install but that's not the issue. My issue with it is the "slowness" of the display!
The best way I can describe it is like a LCD screen with a very weak battery. (and no, my battery is fine)

Looking at it more closely there's something weird going on. When a pixel is turned on it first looks bright blue and then fades to the regular "grey". This causes the update to seem incredibly slow. Being used to the EL BL this seems really bad. I mean, the EL is much much crisper and nicer to look at.

Any ideas why this is? Is there a piece of plastic I forgot to take off? One that I shouldn't have? Maybe I installed it backwards?

Post by **cre8tiveleo** » Mon Feb 27, 2012 4:06 am

All my radios have the white led bl from hk now, didn't like the el at all.

Too dim.

Take a pic of the screen... These are hk bl. (i was playing around with resistors to make the screen darker, er9x is without 1k resistor, the other two are)

Post by **cre8tiveleo** » Mon Feb 27, 2012 4:11 am

Did you install the new foam piece? Or just used the original foam?

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Post by **erazz** » Mon Feb 27, 2012 4:34 am

Yes I did.... Cursed the whole time too.

Personally I like the brightness (or lack thereof) of the EL. But again, the issue isn't the color, ease of installation or anything else. It's the refresh rate that's driving me mad.

wallaguest1 · Post by **wallaguest1** » Mon Feb 27, 2012 5:29 am

i don't undertand what you mean with "slower refresh rate"
the pixel response of the lcd is slower with the led backlight than with EL panel ?

B12 · Post by **B12** » Mon Feb 27, 2012 5:51 am

You have to increase the contrast value when fitting the HK led backlight. Otherwise it makes the display look "fuzzy" and the respond appears slow/weird indeed. It is just needs adjusting for changed conditions. The reason is the led is brighter than the el panel and it shines through the pixels without adding more contrast and it shows up the pixel updates you won't see otherwise. No big deal, been there done that.

Post by **erazz** » Mon Feb 27, 2012 7:34 am

Well the contrast bit did improve it a bit. But now I can see all the scratches in the back

Still, weird behaviour. The "lag" is much improved but still visible.

B12 · Post by **B12** » Mon Feb 27, 2012 10:04 am

It must be that the panel is a bit slow indeed. The bright backlight just makes it visible. You can dim it by fitting the 1k (or something) resistor.

some 2-5k pot might be cool to adjust the brightness depending on lighting conditions. Or maybe a simple controller using LDR resistor
http://www.technologystudent.com/elec1/ldr1.htm

Post by **cre8tiveleo** » Mon Feb 27, 2012 12:53 pm

Maybe the current draw from your bl is eating what's available to the lcd screen? The only time my lcd screen 'lags' is when it gets too cold. The warmer it is, the quicker the response time. That could be it too. leds are only on the side, the El panel lights up entirely. (that small difference of temp could change the lcd response time too) Otherwise, when I had my el installed there was no real difference in response time compared to another radio that had a hk bl in it. (I don't use the hk connector though, pain in the butt disconnectign it, re connecting it, just cuut the wires, added my own resistor and wired it tothe pcb directly (5.5v))

B12 · Post by **B12** » Mon Feb 27, 2012 1:17 pm

The led panel is wired directly to battery power. It should not mess the lcd. Current draw is also minimal (15mA or so) so it should not really affect anything.

Post by **cre8tiveleo** » Mon Feb 27, 2012 1:56 pm

You would think that, but...

Read this thread... And the led bl fix.

viewtopic.php?t=412

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SkyNorth · Post by **SkyNorth** » Mon Feb 27, 2012 4:32 pm

Maybe the Gin bottle was to close to the LCD?

-Brent

Post by **erazz** » Mon Feb 27, 2012 5:21 pm

Nope.... I keep the Gin close by!
Kinda into potato vodka lately... Just a fad..... http://www.chopinvodka.com/

Post by **cre8tiveleo** » Mon Feb 27, 2012 5:22 pm

Mmmm gin.

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MoleHunter · Post by **MoleHunter** » Fri Mar 23, 2012 6:56 am

Women drink gin, not men! They don't call it "mother's ruin" for nothing, you know!

Westy · Post by **Westy** » Fri Mar 23, 2012 7:33 am

..... I have to disagree..... I enjoy Gin ... but only the good stuff "Blue Saphirre" of course.

Post by **erazz** » Fri Mar 23, 2012 11:34 am

Hendricks is very good

But you'r kiwi... You should be drinking 42 below! (great vodka)

Post by **s_mack** » Fri May 04, 2012 3:12 pm

I'm a little late to this party, but I have something to add (or rather, subtract? No.. .multiply!) to the debate.

First off, some history: When I first looked at doing a backlight, EL seemed the natural choice because a) its thin and b) you can cut it to any size so there wouldn't be huge development costs making an LED custom sized for the screen (this was before HK made theirs). I still think EL is the ideal technology for the job. My mistake, some will argue, is that I underestimated people's desire for brightness! I can be oft-quoted as saying "its supposed to be a backlight, not a flashlight!"

The brightness is not a limitation of EL (Ok, there is a limit but its not at that limit), I deliberately set it to be ideal for night flying. That was what I erroneously believed would be the sole purpose of having the backlight. For night flying, you do NOT want bright! You just want "bright enough" to read it... and for that purpose, I stand by my product's brightness, that it is ideal for reading the screen in the dark... comfortably. I did some tests awhile back and confirmed that the EL panel *can be* brighter than the LED backlight can be, so its really not a limitation of the technology.

One thing that IS a limitation (or, rather, a liability) with the technology in how it is highly susceptible to ESD damage. I didn't know that before making the design and, admittedly, I could have done a better job building in protection.

But now for some news: I'm having a problem with my EL panel supplier. When I was getting quotes, I got one good quote and a bunch of much higher quotes. What I didn't know, was that the one good quote was selling from surplus EL stock. They had a few large sheets of it that they were cutting up and selling to me. Now, with no notice at all, they're out of that stock. That's why I currently have red panels because they ran out of blue. I'm shocked they wouldn't tell me this ahead of time, but that's life I suppose. The pain of dealing with an unreliable supplier combined with the frustration of the ESD susceptibility, as well as in response to suggestions by several customers, has led me to a decision to remove the EL backlight function from my future boards. In its place, however, will be advanced support for the HK backlight. I'll also be investigating getting my own LD backlights made. What does "advanced support" mean? Read on...

The problems with the HK LED system, in my opinion are:

they are (relatively) inefficient. Yes, I know people have said (as a couple of posts above) that it only uses xx mA but I think either there's a mistake in logic about how to measure current draw or otherwise there's a wide variance from one unit to the next. HK declares, if I recall correctly, that its something to the order of 90mA and since most LEDs run between 20 and 30mA and there are two of them... it makes sense that its around 40 to 60mA. Not that this is horrible by any means. But how much power they use isn't really a term of efficiency. With the way HK decided to do it (and to their credit, its the way almost EVERYONE does it) via a simple resistor and running them in series directly from battery voltage... well, you don't get the output (brightness) you should given the input.
Its too bright in some situations and/or for some people
You have no control of when it is turned on/off (without somewhat non-trivial modifications)
They simply aren't driven appropriately for the technology. This will be a debated point. Much like EL, which is COMMONLY driven by an inverter but really SHOULD be (for purposes of noise, efficiency, and longevity) driven by an inductor/transistor circuit... the LED is COMMONLY driven by current-limited battery voltage when it SHOULD be driven by a constant current circuit.

To address each of these points, my design will feature:

power efficiency. Using a specialized LED driver designed specifically for the task, it should be significantly more efficient. Whether that will mean less power at the same brightness, or brighter at the same power is TBD. Considering the HK LED backlight is wired in series, there's limits to what I can do here so its possible it won't be as significant as I hope.
Fully dimmable via firmware (once the firmware supports it!). I imagine you should be able to assign one of the pots to the light and have full analog control over the brightness from off to full power. This lets you adjust for the scenario and use as little or as much power for the backlight as you determine appropriate.
By the same token, it will be controlled via firmware rather than simply on/off with the main power switch as it is now.
It will be constant current which will keep the LEDs alive longer and ensure uniform brightness rather than it getting dimmer as your battery runs down.

One final possible benefit - though this isn't my area of expertise - is that we can control the frequency that the LEDs are driven at. So we may be able to mitigate or eliminate the ghosting that Erazz was experiencing. The frequency is controlled by the PWM signal sent to it, so its something that can be played with that I don't have to have pre-set perfectly before production (which is good, because I'd just be guessing).

Anyway, I know some will think its a mistake to ditch EL and support LED... some will call me a hypocrite after defending EL so long... but it is what it is. Going this route means I deal with one supplier instead of two and that makes coordination that much easier as well.

However... one potential downside to the customer, is that before it came with a backlight and was completely solder free. Now it won't come with the backlight (you have to get it from HK unless I can get them to sell me a bunch at a discount) and you'll have to solder it (I think... I'm still working on it).

Let me know your thoughts please.

- Steven

Post by **Rob Thomson** » Fri May 04, 2012 3:29 pm

Hey Steve,

I personally have moved to the Sky9X board - so am not likely to need it, but I think for the 'stock' board users. This is a great idea and worth the effort.

Rob

Post by **s_mack** » Fri May 04, 2012 3:40 pm

You say you "moved to the Sky9x board" like its available. So just for clarification for people reading this (and posts like it - I know it causes confusion which then causes a bunch of questions like "where can I get it?")... it is still beta and only available to a very limited number of people, correct?

- Steven

Post by **cre8tiveleo** » Fri May 04, 2012 3:49 pm

And to clarify, so people don't get confuses, your new board sans el isn't availablet either?

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Post by **s_mack** » Fri May 04, 2012 3:54 pm

huh? Of course not. I think you misread the intent of my post Leo. Or I'm misreading the intent of yours

Feel free to be clear on why you posted that, because it seems perfectly obvious that a board, which I *JUST* wrote is an upcoming design, is not available. My post that you were replying to was for clarification since Rob's post introduced some ambiguity on availability. My response to Rob wasn't meant to be anything but clarification, whereas yours appears to have a little extra flavor to it. So if there's something you wish to say...

Post by **Crucial** » Fri May 04, 2012 4:48 pm

I recently installed the HK backlight and overall I like it. I installed it with the transistor circuit and it's controlled by the firmware. It eliminated the fluctuations of the potentiometer values when the light was on and is a higher brightness making it more useful in low light conditions.

I wasn't unhappy with the EL panels, they did serve their purpose well but I do find myself noticing and appreciating the increased brightness when I am working on something in a dark room or when the radio is in a shadow.

I haven't noticed the problems Erazz was explaining but I haven't looked that closely either.

Post by **s_mack** » Fri May 04, 2012 4:54 pm

Crucial wrote:It eliminated the fluctuations of the potentiometer values when the light was on

can you expand on this please? I don't know what you're referring to. Thanks

- Steven

B12 · Post by **B12** » Fri May 04, 2012 5:02 pm

s_mack wrote:
The problems with the HK LED system, in my opinion are:
they are (relatively) inefficient. Yes, I know people have said (as a couple of posts above) that it only uses xx mA but I think either there's a mistake in logic about how to measure current draw or otherwise there's a wide variance from one unit to the next. HK declares, if I recall correctly, that its something to the order of 90mA and since most LEDs run between 20 and 30mA and there are two of them... it makes sense that its around 40 to 60mA. Not that this is horrible by any means. B

Oh please...I did not expect that kind of BS from you.

I am one of the people who have measured the much debated current draw and obviously messed the whole procedure. I just connected the multimeter in series with the HK Life battery and the radio. Backlight off the current draw was 120mA and backlight on 135mA.

The main problem here seems to be that no matter what you just refuce to accept the fact that the $5 led backlight makes more light with less current draw (=is much more efficient) than your $50 one. It can be proved with elementary school math+physics and it does not become anything else no matter how long you insist.

I admit being rude but I am fed up with people providing false information to promote business. Most propably can filter that but many will believe anyway. Your bolt-on board is a great product and has it's place in the world for sure but please do not try to sell it with values it does not have. Make it sell with it's good points but do not try to lie or make things up to bash competitors.

The HK light has a 470 ohm resistor in series with the leds. I just cannot believe you are not able to calculate the approximate current driving the leds.

Post by **Crucial** » Fri May 04, 2012 5:07 pm

If you look at the ANA screen while the EL backlight is on the values for the potentiometers will fluctuate. As soon as the light goes off the values will stop and stay constant. This was noticable in the "home" screen where you can see the values of the stick postitions from -100 to 100. If a stick was in the middle it would be 0 and when the EL light came on it would bounce around. The flucuaions weren't much only 1 or 2 digits but it was there. It was enough for me to turn off the backlight while calibrating so the values would stay constant.

Post by **Crucial** » Fri May 04, 2012 5:22 pm

I never measured the current draw after putting the HK LED in. I will try and do it tonight. I have a white and a blue IIRC.

Post by **Crucial** » Fri May 04, 2012 5:23 pm

http://www.rcgroups.com/forums/showpost ... ount=15970

I think this explains Rob's post.

Post by **s_mack** » Fri May 04, 2012 6:03 pm

Crucial wrote:If you look at the ANA screen while the EL backlight is on the values for the potentiometers will fluctuate. As soon as the light goes off the values will stop and stay constant. This was noticable in the "home" screen where you can see the values of the stick postitions from -100 to 100. If a stick was in the middle it would be 0 and when the EL light came on it would bounce around. The flucuaions weren't much only 1 or 2 digits but it was there. It was enough for me to turn off the backlight while calibrating so the values would stay constant.

I'm a little confused why this is the first I've heard of this a year+ later! But thanks. I'll check it out (not that there's a lot of point now I guess

)

B12 - wow... pent up anger or something? I'm a little confused at the attack and yes... it was rude. I've got one on the way to me, but up until now I don't have an HK backlight. Directly quoted from their website:

Current Draw: 60~90mA

So I don't know how my statement is BS?! Compared to THEIR declaration of 60 to 90... 15mA seems a bit far-fetched. It seems a number that would be garnered by someone that perhaps doesn't know how to measure Amperage and/or their tools are innaccurate, considering what the manufacturer states and that it is two pretty bright LEDs in series. Does that mean you're absolutely wrong? No, and if you actually read my statement that you quoted, I explained the reasoning behind my assumptions. I never said, "I measured it and it is YY so whoever said XX is an idiot". I don't have to believe your measurements and statements just because you say them. It doesn't mean my counter is "BS" and it certainly doesn't meant I'm "providing false information to promote business". You know what I'm getting fed up with? And not just on my behalf... but to everyone who's making products to benefit this community... is people that CONSTANTLY beat the "profit = evil" drum. I could CARE LESS if you or anyone else buys my board or chooses a different alternative. Why would I? For one, I make hardly anything on these. For two, I'm constantly sold out so I really don't need to spread false information. Speaking of false information, you wrote:

Most propably can filter that but many will believe anyway.

immediately after:

you just refuce [sic] to accept the fact that the $5 led backlight makes more light with less current draw (=is much more efficient) than your $50 one.

Now THAT's BS. My $50 what? First, its $45 not $50 (and if you're including shipping then its not a $5 LED backlight, is it?) but mostly its not a backlight! Its a solderless programmer with an included bonus backlight. A little apples-to-apples please!

I've said many times that the LED backlight has comparative disadvantages and advantages vs EL. In *MY OPINION* (as I constantly qualify it as) it is too bright. You want to see that as a plus, fine... that's your call. But my professing that it isn't perfect is not the same thing as saying it sucks. It doesn't! I never said it did. It is inferior in some ways and superior others. And it is cheap.

I really can't understand the attack. its not a "refusal to accept" - it is pure, honest bewilderment. All I did was come here to update on where things are at with the SP kit and to get some (hopefully constructive) feedback before commiting one way or another. But forget it. I've apparently posted in the wrong place. My mistake.

- Steven

B12 · Post by **B12** » Fri May 04, 2012 6:20 pm

The Hobbyking claim of 60-90mA has been proven false by several people who have actually measured the current draw, period. You simply cannot feed 60-90mA through a 470 ohm resistor with ~10V, period. I still do not get your point. You are supposed to be someone who at least understands basic electronics.

Many people here (not including me) are advanced level hobbyists/professional with electronics. Obviously they do not bother to chime in with this kind of whatever.

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