Forums

LCD Text Displays

Started by Tim Wescott March 17, 2014
It's been a long time (1992?) since I've designed one of these things 
into a product, and at that time the thing was just handed to me with a 
"here, put this in":

http://www.lumex.com/en/products/detail/lcds2/high_low_temp/
character_modules/16_x_2/

Does anyone have any recent mileage with these?  Are there any 
manufacturers that are known to be particularly good or particularly 
bad?  Are there any particular form factors that are fairly standard, so 
that if manufacturer A screws my client over, I can send them across the 
street to manufacturer B for a drop-in replacement?

I'm looking for a module that'll be suitable for small-volume (100-1000/
year) production rates, in outdoor working sorts of temperatures (barely 
freezing to tropical -- maybe -5C to +40C).  Aside from that, the 
environmental requirements aren't at all severe -- no RFI, or vibe.  The 
unit is portable but not hand-held, it won't get daily shocks but may get 
tossed into a truck from time to time.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

On a sunny day (Mon, 17 Mar 2014 13:18:46 -0500) it happened Tim Wescott
<tim@seemywebsite.really> wrote in
<c-KdnW5xENsbobrOnZ2dnUVZ5v2dnZ2d@giganews.com>:

>It's been a long time (1992?) since I've designed one of these things >into a product, and at that time the thing was just handed to me with a >"here, put this in": > >http://www.lumex.com/en/products/detail/lcds2/high_low_temp/ >character_modules/16_x_2/ > >Does anyone have any recent mileage with these? Are there any >manufacturers that are known to be particularly good or particularly >bad? Are there any particular form factors that are fairly standard, so >that if manufacturer A screws my client over, I can send them across the >street to manufacturer B for a drop-in replacement? > >I'm looking for a module that'll be suitable for small-volume (100-1000/ >year) production rates, in outdoor working sorts of temperatures (barely >freezing to tropical -- maybe -5C to +40C). Aside from that, the >environmental requirements aren't at all severe -- no RFI, or vibe. The >unit is portable but not hand-held, it won't get daily shocks but may get >tossed into a truck from time to time.
The little 16x2 LCD moduels go here for about 4 Euro one off. Those are Chinese, and I have used those in different projects without any problems. datasheet says: TRI-T COMPANY LIMITED SPECIFICATION FOR LCD MODULE ORDER NO : CG046-3007-01 MODULE NO.: CG046-3007-W-G-LED04-YG DOC.REVISION A01 These days I would use an OLED. goole.
On Monday, March 17, 2014 2:18:46 PM UTC-4, Tim Wescott wrote:

> It's been a long time (1992?) since I've designed one of these things > > into a product, and at that time the thing was just handed to me with a > > "here, put this in": > > > > http://www.lumex.com/en/products/detail/lcds2/high_low_temp/ > > character_modules/16_x_2/ > > > > Tim Wescott > > Wescott Design Services > > http://www.wescottdesign.com
Look on Ebay for "1602" and price over $2.25. Dan
Tim Wescott <tim@seemywebsite.really> wrote:
> It's been a long time (1992?) since I've designed one of these things > into a product, and at that time the thing was just handed to me with > a "here, put this in":
I did my first one in the dot-com era, when everybody was obssessed about the stock price. I liberated the display from the Nortel Meridian phone in an empty cube, because it came with a nice-looking housing. Drove it from the parallel port and internal power supply of a scrap PC; stock price updated every few minutes. (The official LED one up on the wall only got changed when the secretary remembered, which was about every other morning.) I hung the display on the outside wall of my cube, where it attracted interest. Upshot: I got in trouble for taking apart a phone and Doing Hardware as a Software Guy. Oh well... at least that CEO is in federal prison now, partly for shenanigans related to the stock price. All of the below is based on using that display and some others in a similar way (driven from a PC), and from working with and looking inside various equipment that has those kinds of displays.
> Does anyone have any recent mileage with these?
Yes, a negative experience with two different sizes from the same manufacturer. The problem is that I can't remember the manufacturer for sure.
> Are there any particular form factors that are fairly standard, so > that if manufacturer A screws my client over, I can send them across > the street to manufacturer B for a drop-in replacement?
The 2x16x0.2" seems standard-ish, as does the 4x20x0.4". I haven't seen enough of the other sizes to say. The 16 pins, single row, 0.1" spacing for the main power and data connection also seems to be pretty standard. The connection for any backlighting seems to NOT be standard. Sometimes it's the next two pins after the standard 16, sometimes it's a couple of pins at the side(s) of the display, sometimes there are pairs of pins scattered around. I recall, back in the day, that sometimes the LCD contrast voltage was either higher than what the rest of the LCD ran on (like, +12 vs +5), or negative (somewhere between -3 and -12 or so). I definitely remember having to bring out two voltages from that scrap PC, and I *think* they were +5 and -12. The "weird" voltage never needed much current, like a few mA. I think more recent displays are single-ended or have onboard DC-DC, so they are easier to drive. For the ones that mostly do characters, the Hitachi HD44780 command set seems to be popular and widely cloned. For ones that are more pixel- addressable, I don't know. LCDproc http://lcdproc.omnipotent.net/ is a Linux program to display your PC's CPU load, uptime, etc on an LCD plugged into some port. It has code for the HD44780 commands and I bet it includes variations on them as well. Even if you can't use the code directly, it might tell you things like "for Acme displays, bit 0 is reboot and bit 7 is clear screen, but for A-1 displays, swap those two." This might help in supporting parts from multiple vendors. LCDproc can also make use of two libraries, serdisplib http://serdisplib.sourceforge.net/ and graphlcd http://graphlcd.berlios.de/ , which also have to do with talking to these kinds of displays. Disclaimer: I don't know if the above code is any good or not, only that it exists.
> I'm looking for a module that'll be suitable for small-volume (100- > 1000/year) production rates, in outdoor working sorts of temperatures > (barely freezing to tropical -- maybe -5C to +40C).
If you don't put a contrast knob on it, it will be washed out or unreadable 51% of the time in the field. If you do put a contrast knob on it, 51% of the units will come back with a "blank display/displays all squares" complaint, which will be fixed by adjusting the contrast knob. I have seen some of these that didn't like the cold (0 C or less); they either got faint or slow to change. If the inside of your device is warm, or even if the LED backlight is on, that might be enough to fix this. Matt Roberds
On Mon, 17 Mar 2014 13:18:46 -0500, the renowned Tim Wescott
<tim@seemywebsite.really> wrote:

>It's been a long time (1992?) since I've designed one of these things >into a product, and at that time the thing was just handed to me with a >"here, put this in": > >http://www.lumex.com/en/products/detail/lcds2/high_low_temp/ >character_modules/16_x_2/ > >Does anyone have any recent mileage with these? Are there any >manufacturers that are known to be particularly good or particularly >bad? Are there any particular form factors that are fairly standard, so >that if manufacturer A screws my client over, I can send them across the >street to manufacturer B for a drop-in replacement?
The bigger clunkier ones that don't fit will be the ones with 12 suppliers, the svelt one will be the one with a single flakey supplier.
> >I'm looking for a module that'll be suitable for small-volume (100-1000/ >year) production rates, in outdoor working sorts of temperatures (barely >freezing to tropical -- maybe -5C to +40C). Aside from that, the >environmental requirements aren't at all severe -- no RFI, or vibe. The >unit is portable but not hand-held, it won't get daily shocks but may get >tossed into a truck from time to time.
John's mentioned Newhaven a few times, they seem to have medium-high prices and are probably a decent supplier (I've only used them in couple of low volume projects). They have serial input ones if you don't want to dedicate a port to them (with contrast and backlight control as a bonus). I've had okay results with Truly (Taiwan based) in moderate volume, not sure about how available they are through distribution. The most standard drive method is 4 or 8-bit drive with a 44780-compatible chipset on the board, and operating at 5V Vdd. 4 bit drive ends up taking 7 or 8 port lines. The timing for initialization is no problem provided you follow the datasheet recommendations meticulously. There are only a couple stanard pinouts (single or double row) with the backlight as a wildcard. The contrast voltage usually needs to have something done with it.. I've used a thermistor to get resonable results. Wide temperature range liquid requires different temperature compensation and sometimes a negative bias voltage has to be supplied externally. Contrast and backlight brightness and quality in general is pretty variable, IME. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On Tue, 18 Mar 2014 02:52:52 -0400, Spehro Pefhany wrote:

> On Mon, 17 Mar 2014 13:18:46 -0500, the renowned Tim Wescott > <tim@seemywebsite.really> wrote: > >>It's been a long time (1992?) since I've designed one of these things >>into a product, and at that time the thing was just handed to me with a >>"here, put this in": >> >>http://www.lumex.com/en/products/detail/lcds2/high_low_temp/ >>character_modules/16_x_2/ >> >>Does anyone have any recent mileage with these? Are there any >>manufacturers that are known to be particularly good or particularly >>bad? Are there any particular form factors that are fairly standard, so >>that if manufacturer A screws my client over, I can send them across the >>street to manufacturer B for a drop-in replacement? > > The bigger clunkier ones that don't fit will be the ones with 12 > suppliers, the svelt one will be the one with a single flakey supplier.
Well, of course!
>>I'm looking for a module that'll be suitable for small-volume (100-1000/ >>year) production rates, in outdoor working sorts of temperatures (barely >>freezing to tropical -- maybe -5C to +40C). Aside from that, the >>environmental requirements aren't at all severe -- no RFI, or vibe. The >>unit is portable but not hand-held, it won't get daily shocks but may >>get tossed into a truck from time to time. > > John's mentioned Newhaven a few times, they seem to have medium-high > prices and are probably a decent supplier (I've only used them in couple > of low volume projects). They have serial input ones if you don't want > to dedicate a port to them (with contrast and backlight control as a > bonus). > > I've had okay results with Truly (Taiwan based) in moderate volume, not > sure about how available they are through distribution. > > The most standard drive method is 4 or 8-bit drive with a > 44780-compatible chipset on the board, and operating at 5V Vdd. 4 bit > drive ends up taking 7 or 8 port lines. The timing for initialization is > no problem provided you follow the datasheet recommendations > meticulously. > > There are only a couple stanard pinouts (single or double row) with the > backlight as a wildcard. The contrast voltage usually needs to have > something done with it.. I've used a thermistor to get resonable > results. Wide temperature range liquid requires different temperature > compensation and sometimes a negative bias voltage has to be supplied > externally. Contrast and backlight brightness and quality in general is > pretty variable, IME.
It's for a battery-powered application, so the best backlight of all is the one that's not necessary, at least in decent light. The one time I did this I drove the contrast from a DAC channel, and let the user twiddle it up or down with buttons. Do you happen to know if the contrast voltage vs. temperature curve is documented on these things, or is it something you have to mess with yourself? -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
On Tue, 18 Mar 2014 16:57:06 -0500, Tim Wescott
<tim@seemywebsite.please> wrote:

>On Tue, 18 Mar 2014 02:52:52 -0400, Spehro Pefhany wrote: > >> On Mon, 17 Mar 2014 13:18:46 -0500, the renowned Tim Wescott >> <tim@seemywebsite.really> wrote: >> >>>It's been a long time (1992?) since I've designed one of these things >>>into a product, and at that time the thing was just handed to me with a >>>"here, put this in": >>> >>>http://www.lumex.com/en/products/detail/lcds2/high_low_temp/ >>>character_modules/16_x_2/ >>> >>>Does anyone have any recent mileage with these? Are there any >>>manufacturers that are known to be particularly good or particularly >>>bad? Are there any particular form factors that are fairly standard, so >>>that if manufacturer A screws my client over, I can send them across the >>>street to manufacturer B for a drop-in replacement? >> >> The bigger clunkier ones that don't fit will be the ones with 12 >> suppliers, the svelt one will be the one with a single flakey supplier. > >Well, of course! > >>>I'm looking for a module that'll be suitable for small-volume (100-1000/ >>>year) production rates, in outdoor working sorts of temperatures (barely >>>freezing to tropical -- maybe -5C to +40C). Aside from that, the >>>environmental requirements aren't at all severe -- no RFI, or vibe. The >>>unit is portable but not hand-held, it won't get daily shocks but may >>>get tossed into a truck from time to time. >> >> John's mentioned Newhaven a few times, they seem to have medium-high >> prices and are probably a decent supplier (I've only used them in couple >> of low volume projects). They have serial input ones if you don't want >> to dedicate a port to them (with contrast and backlight control as a >> bonus). >> >> I've had okay results with Truly (Taiwan based) in moderate volume, not >> sure about how available they are through distribution. >> >> The most standard drive method is 4 or 8-bit drive with a >> 44780-compatible chipset on the board, and operating at 5V Vdd. 4 bit >> drive ends up taking 7 or 8 port lines. The timing for initialization is >> no problem provided you follow the datasheet recommendations >> meticulously. >> >> There are only a couple stanard pinouts (single or double row) with the >> backlight as a wildcard. The contrast voltage usually needs to have >> something done with it.. I've used a thermistor to get resonable >> results. Wide temperature range liquid requires different temperature >> compensation and sometimes a negative bias voltage has to be supplied >> externally. Contrast and backlight brightness and quality in general is >> pretty variable, IME. > >It's for a battery-powered application, so the best backlight of all is >the one that's not necessary, at least in decent light. > >The one time I did this I drove the contrast from a DAC channel, and let >the user twiddle it up or down with buttons. Do you happen to know if >the contrast voltage vs. temperature curve is documented on these things, >or is it something you have to mess with yourself?
I don't recall the contrast adj but this is one of the faq's I had looked at: http://www.ekenrooi.net/lcd/lcd.shtml My module was a 4line Optrex DMC-????? display. Just make sure to follow the start up routine. My notes are from 99' Cheers