LCD backlight?

[skyewright]

Hi,

The LCD is working fine now (displaying 1-wire weather sensor data, collected using OWFS on an ALIX 1D), but it would be nice if I could find a way to turn off the backlight. Should that be possible?

 

[sda]

Hi,

The LCD is working fine now (displaying 1-wire weather sensor data, collected using OWFS on an ALIX 1D), but it would be nice if I could find a way to turn off the backlight. Should that be possible?

http://owfs.sourceforge.net/shell_hints.html

 

[skyewright]

http://owfs.sourceforge.net/shell_hints.html

Thanks, but sadly that refers to use of a 1-wire LCD controller (family code FF). The Hobby Boards LCD Driver uses a DS2408 (family code 29), for which the interface is totally different...

If it is possible I suspect that it's a matter of "switching off" pins 15 & 16, but I'm not sure how I'd do that (and I could easily be wrong anyway!)

One thing that puzzles me is this bit (with my emphasis) of the LCD Driver page:

If you use a backlit LCD, the external power must be supplied locally (not over the 1-Wire cable). PLEASE NOTE that if you use locally provided external power, you must remove the JP2 jumper from the LCD Driver board, to prevent the power from being added to the power line in the 1-Wire cable.

If you do not use a backlit LCD, you can optionally use external power provided through the 1-Wire cable. You can provide this power using our 6 Channel Hub or our Power Injector , or you may supply your own.

I am not supplying 'local' external power. The only connection to the LCD Driver board is a 1-wire cable, from a 6 Channel hub. I am using a 'backlit LCD" (the standard one from the Hobby Boards store). The LCD is lit up[1]. Am I doing something I shouldn't?

[1] but I'd like to at least try it with the light off, hence this topic...

 

[ericvic]

It is possible to control the backlight but you have to add a few more components to the board.

You need to remove the following:
R1

You need to add the following:
1 DS2406 on U2
2 2N4403 PNP transistors on Q1 & Q2
2 1k ohm resistors on R3 & R5
2 10k ohm resistors on R4 & R6
1 10 ohm resistor on R7
1 15 ohm resistor on R8

With those components the backlight will be off by default. You can also have low by turning on PIO-B, medium with PIO-A and bright with both PIO-A & PIO-B turned on.

Eric

 

[skyewright]

It is possible to control the backlight but you have to add a few more components to the board.
<SNIP>
With those components the backlight will be off by default. You can also have low by turning on PIO-B, medium with PIO-A and bright with both PIO-A & PIO-B turned on.

Thanks for the reply Eric.

Sadly the likelihood of me developing sufficient soldering skills to deal with surface mount parts is I think vanishingly small.

It would be very nice if 'backlight control' were available as an optional extra on purchase (or maybe [pushing my luck here, I realise] even as a retro-fit option?).

David

 

[ericvic]

David,

If you want to send your LCD driver back to me and cover shipping and the cost of the DS2406 then I would be happy to solder the parts on for you.

Eric

 

[skyewright]

If you want to send your LCD driver back to me and cover shipping and the cost of the DS2406 then I would be happy to solder the parts on for you.

Thank you for that offer. I'll take you up on it. I'll e-mail to let you know when it's been posted.

David