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Bright Future: Jornada 720/680 CCFL to LED upgrade

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joval Page Icon Posted 2022-03-19 4:30 PM
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Shottky diode will likely need swap as well : ss12 only 1 amp 20v, ss34 is 3amp 40v.

Joval
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joval Page Icon Posted 2022-03-19 4:37 PM
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CE Geek - 2022-03-12 12:32 AM

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C:Amie - 2022-03-09 10:31 AM

Problem is John, I have no idea about electronics. If I can manage not to blow something up, it's a good day


Nice to know I'm not the only one here in whose hands a soldering iron is a deadly weapon.


My recent experience suggests ...for once... we are truly equals !! Great minds...??

Joval

Edited by joval 2022-03-19 4:41 PM
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joval Page Icon Posted 2022-03-25 12:08 AM
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Edited by joval 2022-04-01 5:27 AM
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joval Page Icon Posted 2022-03-25 12:10 AM
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FYI: Mission Accomplished!!!

Excuse / forget the last few posts about swapping out components or designing a custom boost converter board "cuz it just t'ain't necessary" my friends!!

This is the secret solution: It's a tiny mini-boost converter for one dollar but rated at 2 amps (we only need about 0.5A) and easily fits into the former CCFL inverter space... but is about 1/3 the length.

There are other parts to fill the remaining space:


1. 2 IRFZ44 power Mosfets:

One, #1, for constant current LED protection
(which the mini-boost converter lacks and on 12 volt
AC power will fry them but not on battery 8.5 volts); its source pin connects directly to the right/negative lead on the Jornada screen ccfl connector/tab.

The other #2 is for the dimmer circuit which gives amazing Low levels never possible
with any CCFL and also delightful Brightness for outdoors (much brighter than my new Laptop screen as I post
this)! This is placed in series with the first #1 Mosfet . It's gate is connected directly to the J680
dimmer lead the thin center tap.

2. A 2N3904 transistor combined with a 100k and a 3.3 ohm resistor to bias the base, which in
turn feeds back to the #1 Mosfet gate to prevent over current.

3. I added a tiny smd 3 Amp self-recovery fuse to the left/positive lead on the J680 ccfl connector tab which connects directly to the 32 LED strip replacing the CCFL tube (to protect the Jornada from any LED or boost converter meltdowns).


Something very interesting is occurring between the 2 Mosfets... when I first set up the circuit without the dimmer circuit mosfet... the constant current Mosfet would get quite warm on max brightness. Now, with both in series and dimming working well (although reversed from ccfl keys) both Mosfet s actually feel cooler than ambient temp... some sort of peltier like effect going on. This leads me to think I can increase the current and brightness further, although it is very readable outdoors unlike the essentially black screen I see with the dated ccfl backlight on my J720

So I'm done tinkering here, just need to mount it all in the case, will follow up with photos, schematics, and detailed "how to" info.

Really really nice... super bright and super dim... Like Never Before! For much less than $15 in parts

Joval




Edited by joval 2022-03-25 1:08 AM
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C:Amie Page Icon Posted 2022-03-25 8:00 AM
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Very cool! Not only have you made it more functional and brighter, but lighter and more battery efficient too by the sounds of it.
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fantablium Page Icon Posted 2022-03-25 8:47 AM
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Joval, this is amazing work! Improved screen brightness combined with your Wifi repeater hack makes the J720 almost modern!!!
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joval Page Icon Posted 2022-03-26 1:27 AM
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Edited by joval 2022-04-01 5:25 AM
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joval Page Icon Posted 2022-03-26 2:00 AM
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C:Amie - 2022-03-25 12:00 AM

Very cool! Not only have you made it more functional and brighter, but lighter and more battery efficient too by the sounds of it.


Yes, thanks. Visibility much improved... big big difference. Over 30 Dimmer increments going from max dark to max bright.

Maybe a bit lighter without that ccfl transformer... like near 1000 volts... been shocked many a time in the past by that thing... nevermore.

The mosfets aren't getting warm... so expect longer battery life (unless always on max brightness).



Quote
fantablium - 2022-03-25 12:47 AM

Joval, this is amazing work! Improved screen brightness combined with your Wifi repeater hack makes the J720 almost modern!!!


Thank you, feedback much appreciated!

So nice to go outside with the little beastie and actually see the screen... with ease!

That modern "instant on"... of LEDS, no waiting for the CCFL to slowly warm up.

I can actually cruise the internet in text mode using frogfind.com and read webpages in text and in another window, view small images using google search... all as a stand-alone device with the built-in Esp8266 wifi-repeater ( or bridge) Heaven, absolute heaven... even for any atheists out there... irrefutable evidence ==> Heaven does exist.

I actually used the Jornada720 as reference during my recent soldering up the dimming circuit addition ... frogfind.com provided the instructables sites list of components: transistors, resistors, equations for setting current. Using google search , I then brought up a small image/picture of the schematic which I then followed... to pleasing success. Very Handy... internet access!

(Thanks again to ntware and Jake for getting the wifi-repeater/frogfind.com/Retro-Proxy "synergistic combo " idea going... door-opening in its impact (in WinCE mode).

Joval

Edited by joval 2022-03-26 2:13 AM
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joval Page Icon Posted 2022-03-30 5:53 PM
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Hi All!! OK it's looking good.

Here are photos of my Jornada 690 with the LED backlight upgrade... all self contained inside the screen. Only change is brightness/dimmer keys are reversed... there are about 50 increments from super bright for outdoors ( ) to super dim ( can see faint dark image but not readable) !! Obvious improvement in battery life on low setting AFAIK.

Brightness setting is mid range or so, bright overcast morning light... FYI can go much brighter! And of course "instant on" full brightness, no warm-up, etc.

The J690 is Surfing the web ( er,... maybe crawling the web) via an Aironet 340 open Wifi card to ESP8266 to WPA2 to WRP proxy. Nice for viewing reference articles like Wickedpedia, britannica, various transistor tutorials, schematics... as well as HPCFactor forums. They are actually useful... devices for such reference work. So maybe the Jornada 680/690 is not so bad a choice afterall... play solitaire while downloading.

Anyway new backlight working well... looking to downsize transistors to smaller surface mount as the 1RFZ44's fit but by a hair.

best regards,

Joval

Edited by joval 2022-03-30 6:08 PM




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Jake Page Icon Posted 2022-03-30 7:58 PM
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Fantastic work. So I'm certain, your ESP is now internal, within the machine itself? Or are you accessing it in another way?

Jake
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joval Page Icon Posted 2022-03-31 1:53 AM
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Jake - 2022-03-30 11:58 AM

Fantastic work. So I'm certain, your ESP is now internal, within the machine itself? Or are you accessing it in another way?

Jake


For the Jornada 720, by removing internal telephone modem "board" (under the right side of keyboard... which is just plugged in and taped down" and replacing it with a thin version of ESP8266 combined with makeshift long wire for antenna, and stealing power from the capacitor Stefan mentioned in his USB hack, and adding a push button switch where the phone line connector was==>

Then.... esp8266 is internal on J720, only powers up or down when J720 is turned on or off or auto-off (should you forget and walk away) , and/or use push button switch when wifi/esp8266 not needed. Very versatile and easy to save power, minimize "open wifi" security risk, etc. Has great wifi range, too.

The LED upgrade works the same for either J690/680 or J720 as internally the screens are identical (except 256 vs 64k color resolution)... thus I show a J690 converted to LED backlight ( which is J680 with 32MB ram). I did change the 2N3904 "feedback" transistor to a 2N2222, BTW. More to come...

There isn't space or a plug in modem on the J690 so no room for ESP8266 so I'm using a postage stamp size external ESP8266 running from micro-usb to single cell lithium phone charger ... as wifi-repeater/bridge ...lasts for hours but must remember to disconnect (via telnet or web gui or unplug usb -- easiest).

I just looked under j690 keyboard ==> Perhaps removing the soldered Connectex modem chip under the keyboard would permit enough room for an esp8266... a future project, IMO.

FYI, heard a weird buzzing sound ... maybe like your issue... when ribbon cable to backlight had poor connection at the ccfl inverter end. I soldered the LED boost converter directly to the 3 ribbon tabs/taps (with a "self-healing fuse" on the power lead).. sound disappeared, no problem since. Could just be a loose connection.

Joval



Edited by joval 2022-03-31 4:16 AM
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Jake Page Icon Posted 2022-03-31 2:55 PM
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Hmm. Perhaps that is my issue. They're just extraordinary, these hardware mods. Does the wifi card see the esp as a router choice? Meaning a user can choose b/w an esp connection and another router?

Jake
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joval Page Icon Posted 2022-04-01 4:09 AM
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Hi Jake.... yes the Esp appears as an open / no security router that acts as a bridge to your home router for internet connection. So any wifi computer, tablet, smart phone will see its SSID and can log on... to keep others off your network, you can limit "max_clients" to "1", so nobody can connect except your J720... which is what I do much of the time. And when you turn off the J720, the esp turns off aas well. I like to connect.. use frogfind or WRP and download an article/webpage... and turn off esp with the push button switch... If something else needs my attention elsewhere, I just press the J720 off button and come back later and resume by pressing the J720 on button... wifi reconnects and resume. For most part it works quite well.. ...joval via J720/WinCE/open wifi to Esp8266_WPA2/WRP_proxy/PIE4 (again!)

Edited by joval 2022-04-01 4:12 AM
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joval Page Icon Posted 2022-04-01 6:22 PM
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FYI... some "before and after" LED backlight upgrade photos, now on 2 of my Jornada 720's... in bright morning direct sunlight. Both set to Max brightness.. Never going back!

Joval

Edited by joval 2022-04-01 6:32 PM




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Jake Page Icon Posted 2022-04-01 7:04 PM
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I'm telling you, Joval, if you had been on the production line, HP would still be making these things.

Jake
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