Post by thread:[EE:] Backlight levels

Following on from my earlier question about light level measurements... I now have a voltage going into a PIC's ADC that goes between 0V (Darkness) to +4.5V (Sunlight). It's derived from a old selenium PV cell I found and a logarithmic amplifier. So, my next problem is now should I use the ADC value to set the PWM output that is controlling the LCD's LED back light. Should the back light be BRIGHT at night and OFF in the day ? Or DIM at night and during the day and BRIGHT at dawn+dusk ? Is there any guidance where displays are used in safety critical systems (*) where display brightness is controlled to achieve maximum readability under varying lighting levels ? Peter (*) Not that my alarm clock will be a safety critical system of course !

> Should the back light be BRIGHT at night and OFF in the day ? > Or DIM at night and during the day and BRIGHT at dawn+dusk ? A lot of what you're asking really depends on the user. IME displays on things like bedside clocks are dim at night. Might just be psycho- logical, knowing that a light is dimmer whilst you're trying to sleep Thought about controlling the contrast too ? > (*) Not that my alarm clock will be a safety critical system > of course ! Oh, there are times when it's not safe to wake me up, like when I've been up programming all night and crawled into bed in the wee hours. You really really need a nothing phone call first thing in the morning (but I do know about displaced anger - if I didn't tell anyone to not wake me, it's my fault if they do)

Add a IR emitter/sensor and when you touch it with your finger at night it could go bright. Bill ----- Original Message ----- From: "Jinx" <spam_OUTjoecolquittTakeThisOuTclear.net.nz> To: "Microcontroller discussion list - Public." <.....piclistKILLspam@spam@mit.edu> Sent: Saturday, June 11, 2005 4:38 AM Subject: Re: [EE:] Backlight levels {Quote hidden}> > Should the back light be BRIGHT at night and OFF in the day ? > > Or DIM at night and during the day and BRIGHT at dawn+dusk ? > > A lot of what you're asking really depends on the user. IME displays > on things like bedside clocks are dim at night. Might just be psycho- > logical, knowing that a light is dimmer whilst you're trying to sleep > > Thought about controlling the contrast too ? > > > (*) Not that my alarm clock will be a safety critical system > > of course ! > > Oh, there are times when it's not safe to wake me up, like when > I've been up programming all night and crawled into bed in the > wee hours. You really really need a nothing phone call first thing > in the morning (but I do know about displaced anger - if I didn't > tell anyone to not wake me, it's my fault if they do) > > --

Why not just use a PLED display. It is readable day and night, and requires NO backlight. Charles Linquist Bill & Pookie wrote: > Add a IR emitter/sensor and when you touch it with your finger at night it > could go bright. > > Bill > > {Original Message removed}

I think this will depend on your application and your particular display. Some LCDs are very hard to read without the backlight. In those cases, you may want the backlight to be quite bright in the daytime. In general, you don't want it to be too bright at night because you don't want to be looking into the dark and seeing left over images of the display. My car has LCDs for most of the dash, and it has a very bright backlight so it is easy to read in all but the brightest sunlight. However, when I turn on the headlights, the display dims so as to prevent interfering with my dark vision. --McD {Original Message removed}

I forgot to mention - PLEDS drive exactly like LCDs, cost less than LCDs and draw 40mA max. I have even driven the whole display from one PIC pin. For a picture of my PLED clock, go to http://www.charleslinquist.com/clock The pictures really don't do the display justice, since this one still has the polyethylene protective film over the display to protect the glass. Charles Linquist

Charles Linquist wrote : > For a picture of my PLED clock, go to http://www.charleslinquist.com/clock > > The pictures really don't do the display justice,... But are still 1.4, 2.6 and 2.7 *MB each* in size !! I'm pretty sure that 80-100 K would have been enough... Jan-Erik.

Sorry for the big pics. I have really high bandwidth here at home, and I forget that big files can be a problem for some. And Peter, yours may look nicer, but my display costs $9, and I wrote the code in about 15 minutes. My whole clock consumes less than 50mA display included. Peter Onion wrote: {Quote hidden}> On Sat, 2005-06-11 at 07:10 -0700, Charles Linquist wrote: > > >>For a picture of my PLED clock, go to http://www.charleslinquist.com/clock > > > I think mine looks nicer ;-) > www.btinternet.com/~Peter.Onion/PhaseData/p002140.jpg > Peter > >

On Sat, 2005-06-11 at 07:34 -0700, Charles Linquist wrote: > And Peter, yours may look nicer, but my display costs $9, and I wrote > the code in about 15 minutes. My whole clock consumes less than 50mA > display included. When did this become a contest ? Peter

David P Harris wrote: > Charles Linquist wrote: > >> And Peter, yours may look nicer, but my display costs $9, ..... > > > Where did you get one for $9? > > David > > http://www.onestopdisplays.net You may have to pay a bit more, we buy them in 100's Part # on the back of mine is OSD2002BYPNJB 20 chars X 2 lines. Charles Linquist

At 08:49 AM 6/11/2005 -0700, you wrote: >David P Harris wrote: >>Charles Linquist wrote: >> >>>And Peter, yours may look nicer, but my display costs $9, ..... >> >>Where did you get one for $9? >>David >http://www.onestopdisplays.net > > >You may have to pay a bit more, we buy them in 100's > >Part # on the back of mine is OSD2002BYPNJB >20 chars X 2 lines. > >Charles Linquist OLED/PLED lifetime is an issue in some applications. Especially at elevated temperature, it can be surprisingly brief. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" speffKILLspaminterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com ->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff

We have a lot of these with well over a year on them. Most have been in room-temperature environments, but none have noticeable degradation. I watched one run in an environmental chamber at 60 degrees C for one hour (along with the PIC, of course). That was last summer. Last I heard it was still working fine. Lockheed-Martin buys a lot of them from us. Can't tell you what they do with all of them, though! Charles Linquist Spehro Pefhany wrote: {Quote hidden}> > > OLED/PLED lifetime is an issue in some applications. Especially at > elevated temperature, it can be surprisingly brief. > > Best regards, > > Spehro Pefhany --"it's the network..." "The Journey is the >

Spehro Pefhany wrote: > OLED/PLED lifetime is an issue in some applications. Especially at > elevated temperature, it can be surprisingly brief. So what do "OLED" and "PLED" stand for? ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com

Peter Onion wrote: >> And Peter, yours may look nicer, but my display costs $9, and I wrote >> the code in about 15 minutes. My whole clock consumes less than 50mA >> display included. > > When did this become a contest ? Right about when you said "mine looks better than yours". ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com

I think OLED stands for Organic Light Emitting Diode and PLED stands for Polymeric Light Emitting Diode. If someone knows more, please speak up! Olin Lathrop wrote: {Quote hidden}> Spehro Pefhany wrote: > >>OLED/PLED lifetime is an issue in some applications. Especially at >>elevated temperature, it can be surprisingly brief. > > > So what do "OLED" and "PLED" stand for? > > ***************************************************************** > Embed Inc, embedded system specialists in Littleton Massachusetts > (978) 742-9014, http://www.embedinc.com

On Sat, 2005-06-11 at 15:41 -0400, Olin Lathrop wrote: > Peter Onion wrote: > >> And Peter, yours may look nicer, but my display costs $9, and I wrote > >> the code in about 15 minutes. My whole clock consumes less than 50mA > >> display included. > > > > When did this become a contest ? > > Right about when you said "mine looks better than yours". Except I didn't say that... I said "I think mine looks nicer ;-)" Note I used "nicer" to try to avoid any potential "mine's better than your's" that would enevitably followed, and I used a smiley to indicate I was not being terribly serious about the comparison. Peter

On Jun 11, 2005, at 7:34 AM, Charles Linquist wrote: > my display costs $9, and I wrote the code in about 15 minutes. Ok, I'll bite. Where does one get an LCD-compatible, low power PLED display for $9? > My whole clock consumes less than 50mA display included. > That *is* a lot compared to pure LCD solutions (but they might consume 50mA just in the backlight. And we're back on-topic...) BillW

On Sat, 2005-06-11 at 15:41 -0400, Olin Lathrop wrote: > > > > When did this become a contest ? > > Right about when you said "mine looks better than yours". Please, if you are going to quote me, make an effort to get it right ! Peter

On Sat, 2005-06-11 at 13:15 -0700, William Chops Westfield wrote: > That *is* a lot compared to pure LCD solutions (but they might consume > 50mA just in the backlight. And we're back on-topic...) The back light on mine takes about 85mA at 5V at 100% brightness. Peter

At 12:53 PM 6/11/2005 -0700, you wrote: >I think OLED stands for Organic Light Emitting Diode and >PLED stands for Polymeric Light Emitting Diode. > >If someone knows more, please speak up! Yes, that's right (Polymer Light Emitting Diode is what I see for the latter. A very interesting display technology, already in use in some consumer products (Pioneer had the first serious application that I know of, in their colorful automotive stereo displays). Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffKILLspam.....interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com

In message <EraseME42AB07FC.1080008spam_OUTTakeThisOuTlinquist.net> Charles Linquist <charlesspam_OUTlinquist.net> wrote: > http://www.onestopdisplays.net > > You may have to pay a bit more, we buy them in 100's > > Part # on the back of mine is OSD2002BYPNJB > 20 chars X 2 lines. That is a seriously nice display.. Anyone know of a UK or European source for OLED displays (either text or graphics type)? I've been looking into using a display from a junked Samsung mobile phone, but Samsung aren't too keen on providing me (or anyone else for that matter it seems) with a copy of the datasheet for the controller IC or the display. Well, not without a nice large (>1000 units) order anyway... Later. -- Phil. | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB, @spam@philpemKILLspamphilpem.me.uk | ViewFinder, 10BaseT Ethernet, 2-slice, http://www.philpem.me.uk/ | 48xCD, ARCINv6c IDE, SCSI ... All wiyht. Rho sritched mg kegtops awound?

In message <KILLspamf27f3a1d1f758e6ff94227bc3cf3ddabKILLspammac.com>> William "Chops" Westfield <RemoveMEwestfwTakeThisOuTmac.com> wrote: > That *is* a lot compared to pure LCD solutions (but they might consume > 50mA just in the backlight. And we're back on-topic...) You think that's bad? I've got a Samsung VFD that pulls 200mA! Speaking of which, anyone know of a source of reasonably cheap LCD-compatible VFDs? I've got a few Samsung 20T202DA1Js, but I want more :) Later. -- Phil. | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB, spamBeGonephilpemspamBeGonephilpem.me.uk | ViewFinder, 10BaseT Ethernet, 2-slice, http://www.philpem.me.uk/ | 48xCD, ARCINv6c IDE, SCSI ... My hard disk is full! Maybe I'll try this message section thing.

Philip Pemberton wrote: >Speaking of which, anyone know of a source of reasonably cheap LCD-compatible >VFDs? I've got a few Samsung 20T202DA1Js, but I want more :) > > I bought a couple extra VFDs from a piclister a while back when he did an [AD] for an assortment of stuff. Perhaps he'll read this and chime in if he has more... Aaron