I was wondering if the backlight of a 4x20 LCD is supposed to get hot - I just got it and wired it up myself. I've got it hooked to a 10k trim-pot but it's kinda fidgety. when the backlight is dimmed a bit it stays cool so I know that's what is generating the heat. I've had displays before but never a backlit one so I'm not sure if it's normal.
My vfd gets quite toasty when its on. Hotter then you would want to touch at all. Tho that is a whole different animal. Is it an Led or incadescent backlight? I am not sure about the led ones but I know incadescent backlights get a bit warm. -Nesbit
Hmm most get a little bit warm (they normally have 10+ surface mount LED's lighting them, not much heat there but enough). If it's getting hot (the display not the cips on the back) then I'd suggest the voltage you're dropping across them at that 10k pot setting is too much, check out the backlight's max forward voltage in your display's datasheet... could well be 4V or less. Cheers, Rob. p.s. welcome to the boards!
Thanks! I think the datasheet said it was +5v.. I also remember seeing that I was supposed to use a 100-ohm trim-pot on the backlight, not a 10k-ohm - that may be my problem but I'd figure it wouldn't make that big of a difference. The display is a Seiko L2014 LED Backlit (a cool orange color by the way) this little guy: (Pic from GideonTech)
So since I'm planning on putting this in a project box, a small fan in there with it would be a good idea? I'm still worried about running the backlight full-tilt. I don't want to damage the display (it got REALLY hot) but if it was designed that way wouldn't it be safe still? It seemed to function fine even though it was burning me to touch it.. Very strange.
Check the datasheet, the backlight LED's have a maximum specified current, DON'T EXCEED THAT. A 10k pot is way off for controlling the backlight, put a 100ohm pot in there and you'll be able to control the current better.
Yeah - I read 100-ohm for the backlight but silly RadioShack (both of them down here) only had 10k's right now.. I guess I'll have to order one.
would you be talking about the MO lcd specifically.. i got the bit tech deal, and remember askign Henry about that, but with the wide voltage option, thats just the voltage regulator cranking out the heat.. its normal.. -scoob8000
heatsinks? old 486 gold one would work, and it would match your backlighting mod it to the max baby! more cooling!
Heh..Heatsinks on an LCD, I never thought it'd come to this . I probably will.. Oh, and although the screen is blue when off, it turns orange when on. I should be putting it into its box tonight. I'll post pics later. -oh, and I Finally went out & bought LCDC and it is happily running my monster BG Micro VFD, but since this little 4x20 is parallel, I'll have to stick with LCD Smartie (unless someone knows how to get LCDC to do parallel displays.)
If you crank up the resistance on the backlight you get a nice inverted greenish display. I've had the resistance too low and got it to get really hot and wash out. After cooling for a while it worked again... Best to keep an eye on it for a while when you choose a resistance if it's rather low... Mine runs kinda warm, but not hot enough that I'm concerned. However, I do get a little bit of circulation where it's at so who knows in a confined space...
What resistor/trim-pot, etc. did you use? I'm still using this 10k but I have to keep it dimmed a bit so it dosen's get hot. It works ok but I'd rather fix it that leave it the way it is.
I used whatever the GT diagram said, I'm off to class and no time to look, i think it's like 100 ohm... Do you have a multi-turn 10k or something, cause a single turn would seem to give you very little control except for many levels of very dim Once I found a level I liked I measured it and replaced with regular resistors of the same value since I felt no need to really mess with it... I would guess it's at 30ish or something, but it's been a few months and I dont remember
You must remember that if the feed voltage is more than 5V. (that was the LED voltage? right?) The LEDs will be fed with that specified voltage when the potmeeter is on the lowest resistance ( 0 Ohm/short cicuit). So if you have 7 volts and you turn your potmeeter to the lowest resistance the LEDs will be fed with 7 volts. What you need to do is to find a resistor to mount in serial with the pot. to protect the leds when the pot. is at the told point. The new resistors Ohm value depends on the feeding voltage If this is not the problem forget trying to interpret my messy text
Yeah, I found some 100-ohm trim-pots online (where, I can't remember but I'll say when the name comes to me) and got 3 of them for future projects. They were about $1.50 apiece.
