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[on:]

hi,

got a really strange lcd problem, im using a bog standard 4 line 20 character display no problems at all been working fine for a couple of months now

i noticed a few times early on the display acting strangely the characters went really dim couldnt work out what was causing it.

fast faward 2 months finally worked out what is causing it, had the display close to a window the display went really dim all characters,  then took it away from the strong light not sun light into a normal lit room the characters returned to normal operation

is this normal?   

[Reply #1 on:]

Doesn't sound 'normal' to me but it COULD be some kind of "auto contrast" feature going wrong.

Try shading different parts of the display to see if one particular area or component is sensitive to light.

[Reply #2 on:]

hi john
its really strange, ive tryed blocking out different parts of the display does this same gets dim in direct light, as soon as you angle it out of the light characters go bright a fraction of a second later, like an auto contrast display i soppose, but its not an auto contrast display
 
but its defiantly sensitive to bright natural light, not sensitive to artificial light at all, its one of these ebay specials, had a really good look at the display cant see any sort of light sensor

been playing with it for ages now its defiantly trying to auto contrast, in some way.

(ive got another display an auto contrast, it has a small sensor in the black front face, nothing like this one)

http://www.ebay.co.uk/itm/160930204992?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

[Reply #3 on:]

..

. is this normal?

You really should try to get some input from forum member liudr.  He has pretty much been staying away from the 'Displays' section for the past few months but you should be able to find him in the 'Project Guidance' or the 'Bar Sport section.

Don

[Reply #4 on:]

Th OP reached me via PM. Are you using a display with black characters or are the characters lit by back light?

[Reply #5 on:]

hi liudr thanks for taking a look

its backlit blue, white characters

here is the display


http://www.ebay.co.uk/itm/160930204992?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

[Reply #6 on:]

I have a similar display and I had to keep the back light on to see the characters. Just relying on ambient light is not enough. Are you using the back light?

[Reply #7 on:]

How did you wire up the contrast potmeter ?

[Reply #8 on:]

this is my lcd setup

[Reply #9 on:]

LCD pins 15 and 16 are not just 5V and GND. They are the connected to the LED back light. You need a current-limiting resistor.

[Reply #10 on:]

hi liudr, yes i understand that, there is a 680r current limiting resistor on the lcd itself