Old LCD board modification to allow fw 3.9.0 brightness control ?  

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

There are some pictures and schematics in the github thread on the feature. Probably easier to source a third party clone than mod the existing board - needs to be a "LDO-RRLCD-A004" clone. A003 did not have the backlight control support.

https://github.com/prusa3d/Prusa-Firmware/pull/2270

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

I poked at this a bit, should be possible but you will need to alter the board. I believe the following will work, but have not tested yet. Plan to try it at some point. 

-Need 100 0hm resistor, 100k pullup, general purpose NPN transistor.

- Will need to cut LEDK trace or remove the pin from the LCD connection as it's grounded in the 003 board. 

- 100ohm goes from E2 P1 to base of transistor. 100K acts as a pullup resistor to + 5v

-Transistor emitter to ground

-Transistor collector to LED_K on LCD module, after removing pin to backplane board.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

@vintagepc

Thank you very much for the info! It seems an easy modification. On the old board the pin in the connector is not marked LEDK but is connected to the motherboard the same way.

Best regards, Vincenzo

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

I actually wired it up myself just now, will try it out after my current print finishes. If it works I'll post a pic.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Success! After making the mod, the brightness menu appears and I can control the backlight. 

My parts bin has mostly through hole parts so I scavenged what I had. I used a 2N2222A transistor but any general purpose NPN is fine. 

My LCD has pads top and bottom as it's an aftermarket replacement I home-brewed from this thread: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-user-mods-octoprint-enclosures-nozzles-.../a-very-much-needed-improvement/

As it is I'm using LEDA as my +5v source, the backplane LED_K as GND (I pulled out the connecting pin between the backplane and display module). There's a pad for E2P1 (PWR_LED) and an unused component, onto which I tacked the 100 ohm resistor. 

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Excellent!

Thanks again!

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Good info here, @vintagepc. I'll probably end up doing similar to you and tacking on my own transistor circuit from my misc parts bin.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

The LCD display unit number can be easily seen underneath with a mirror (lower right side).  Just wanted to verify something.   In the case of A004 is this board compatible without modification using the new proposed firmware?  Conversely, can the older A003 unit previously provided by Prusa be modified as above?

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Yes and yes. Both of your questions were already answered had you looked at the picture showing the mod on an A003, and read the previous posts noting that A004 works out of the box.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Thank you, just wanted to verify.  “Clone” is not necessarily the same......

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

well, I did say the board  needs to be a "LDO-RRLCD-A004" clone. Implying the part number given is the original and any clone of that specific part should work.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

I had cause to look underneath my printer (Mk3S kit) yesterday and was surprised to see that I have the LDO-RRLCD-A004 display board. According to Prusa, these boards were supplied with printers 'manufactured in the 2nd half of the 2019'.

Well, I ordered my Mk3S in mid-May and it was delivered at the end of that month.  Might be worth a check if you are interested in the screen dimming feature.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

I had my display replaced last year (in August) by Prusa under warranty so just checked the details.

They are: LCD 2004A-V3.0 and LDO-RRLCD-A004

I just installed the 3.9.0 beta firmware and the brightness option still doesn't show.

I can't work out why given it is meant to work under the A0004 version of the display board.

Anyone have any ideas?

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

check your LCD cables. If they are not seated right it could cause the firmware not to detect that the display is capable. 

Otherwise... post a picture of the back of your display board. 

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Cables look OK.

Here is a picture of the board.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

The number on the sticker is LDO-RRLCD-A005

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Please post a full picture, not just the labels. We/I can't see whether it has the correct circuitry for backlight control from those.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

@vintagepc

Thanks.

I'll need to dismantle somewhat to get to the back of the board. Exactly which part of the board should I be looking at to determine which backlight control circuitry it has? I may be able to get a photo of that part of the board without pulling it apart too much.

RE: Old LCD board modification to allow fw 3.9.0 brightness control ?

Sure, there's a picture of the circuitry and some more details as to what your board needs here:

https://github.com/prusa3d/Prusa-Firmware/pull/2270