DLT display very dim

Hi, newbie here. I moved into a new (old) house about 6 months ago that had a whole-of-house C-Bus system installed 4 years ago. I've had fun tweaking it all to get it how I like it. Including programming the logic engine to talk to a Raspberry Pi to control my Hue lights as well (Hue scenes selectable on my c-bus CTC and my Wiser2 phone app!), so I can set scenes that are a combination of c-bus dimmers and hue globes. But that's another story.

The existing system had two DLT's that I thought were working as designed. However, I bought a new one which arrived yesterday, and I was impressed with how bright the display was, and certainly much brighter than the existing two units (which are probably equivalent to about 5% on the new one). So I checked the brightness settings for the existing ones, and all is correct. I even changed one to follow a group, and that worked fine as well (but just changing from off to very dim).

So, has anyone experienced this before? Is the backlight for the LCD panel LED or fluorescent based? Fluoros dim over time, but LED should be fine. Any thoughts?

Thanks

 

I suspect I might have been too long-winded there. So to put it more simply, is it a known issue that DLT units lose their brightness over time, and what settings are thought to minimise it (if it is an issue)?

Thanks.

 

Forgot about this problem until today when I installed and old DLT I had lying around . I have a couple that have the same issue, didnt really notice it until I also purchased a couple of new ones.
Checking the toolkit I found the "trained" installer had set them at 100%, seems to kill the backlight after about 5yrs so swapped them out.
Now I protect the new ones using a pascal controller that changes the level of a Group that is used to set the DLT backlight, The old one I have in my hand appears to have some sort of fluro backing plate bonded to the lcd so doubt there is a fix.

Feel free to use/modify this script I used to run on my pi prior to getting the pascal controller

#!/usr/bin/expect -f
set dl [lindex $argv 0];
set hostname "yourhostname"
set port "20023"
set cgate_prompt "Clipsal C-Gate Version"
set address "254/56/99"
set level "$dl%"

spawn telnet $hostname $port
expect -re "$cgate_prompt" {
exp_send "\r"
sleep 2
exp_send "ramp $address $level 2s\r"
exp_send_user "sent c-gate command\n"
} eof {
exp_send_user "could not connect to $hostname\n"
}
expect "200 OK:"
exp_send "exit\r"
exp_send_user "Light Switched On $level"



Then via cron I used the following

# CBUS DLT led light level adjustment
# early morning
#30 5 * * * /usr/local/bin/dlt_level.exp 10 > /dev/null 2>&1
# daytime
#0 8 * * * /usr/local/bin/dlt_level.exp 5 > /dev/null 2>&1
# early evening
#0 17 * * * /usr/local/bin/dlt_level.exp 15 > /dev/null 2>&1
# evening
#0 21 * * * /usr/local/bin/dlt_level.exp 10 > /dev/null 2>&1
# late
#0 22 * * * /usr/local/bin/dlt_level.exp 5 > /dev/null 2>&1
#

 

Actually it appears to be using 8 leds down the l/h side , time to investigate things a bit more to see if they can be separated from the panel and replaced

 

Thanks for the reply, cheekymonkey!

Well, it seems it is a known problem. I note that my older DLTs had a vertical strip of black potting goo to the left of, and the same height as, the LCD display itself. My newer DLT has a tinned piece of plate metal where the black potting material previously was, and that extends as a thin metal strip all the way around the LCD display itself. Hoping that this new "metal plate" design uses LEDs (anyone know?).

Regarding the pi, thanks for the code. I'm in the progress of migrating all my Pascal scripts from the Wiser2 Logic Engine over to the Lua scripting language on the 5500SHAC. The net result will be more running on the SHAC and less on the pi (since I had to have things running on the pi that Pascal couldn't do). Lua has more modern network interfacing capability.

I'm presently recoding my Hue light bulb and scene control into Lua scripts, since the SHAC more capably interfaces directly to the Hue bridge (I've got it working, just tidying up). I'm hopeful of posting my scripts in a new post for others to use. Give me time!

 

Would you describe your unit (the one with the 8 leds) as the black potting goo one, or the tinned sheetmetal one?

 

Mine has the black potted almost silicon material, btw it is only attached to the lcd module which can be separated with some heat and floss as per my pic. I'm sure the tin foil of the newer ones must help the back lighting a fair bit.
Re the leds they appear to be 4 strings of 2 leds with a 10ohm resistor, and at 100% I measured 5.9v to the module, maybe a bit low but there is no way I could debug the led driving cct. They look to be 0603 smd's so I've ordered a bunch of so called bright white ones from ebay (queue 6week wait) and whilst they are small I think I should be able to replace them.
In the mean time I tried bridging one of the resistors but it didnt help, so now we wait.

Wow the 5500SHAC is too expensive for me, I recently added Homebridge running on a small shared purpose vm, works great and interfaces with my Elk (Ness) M1G would run on your pi fine also

 

Just reading the docos for the 5500shac can do a fair bit but I do like Homebrdge how I can set it to auto turn the lights on when we arrive home and how it integrates with Siri
Definitely 0603's I remembered I had bought some incorrect sized red smd leds a while ago, removed the old ones using my cheap ebay hot air station, and then re soldered the red ones again just using air, was pretty fiddly but got it done.
Turns out if I have 2 installed they draw so much current the others fail to light, if the ones that turn up are just as bright I could probably get away with only replacing one in each string.
The screen pic is with it at 100%

 

Thanks to both of you that have taken the time to reply (and to cheekymonkey for a pretty detailed investigation!). I agree LEDs are finite, and running at a lower brightness unless touched would help considerably. I'm a product designer in the electronics industry and I also agree that LED efficiency and lifetime has come a long way in the last 10-15 years!