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Raspberry pi lcd screen?

Community Veteran
Posts: 6,611
Thanks: 209
Fixes: 15
Registered: 16-02-2009

Raspberry pi lcd screen?

I am trying to get an 2x16 lcd working on my pi.
I have it wired fine, can get text on it, BUT the contrast is way OFF.
I have to have it at an angle to read the text at all.
At the mo I have it wired as :
Pin 2,15 5V
Pin 1,3,5,16 0V
Pin 11-14 data
Pin 4 to gpio 7
ping 6 to gpio 8
Any ideas?
8 REPLIES
Community Veteran
Posts: 3,380
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Registered: 18-01-2013

Re: Raspberry pi lcd screen?

Normally you put something like a 1k pot with each wiper end to +5v and 0v the middle wire from the pot goes to the contrast adjust on the LCD.
*Edit - you need to put this to Vee normally. If you have an extended temperature LCD then Vee can sometimes go negative and you need to mess with charge pumps to sort this.
Community Veteran
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Registered: 15-06-2007

Re: Raspberry pi lcd screen?

This is too complicated for Chit Chat so to Hardware it has gone
Community Veteran
Posts: 3,380
Thanks: 2
Registered: 18-01-2013

Re: Raspberry pi lcd screen?

Pin 3 (Vee)
5v -> 1k pot left track
0v -> 1k pot right track
Pin 3 (Vee) -> centre wiper of pot
You could probably go higher than 1K if you've only got  higher values. You could also grab a couple of 1k resistors and make a potential divider from those to produce 2.5v from the 5v supply and try feeding Vee with that.
Community Veteran
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Registered: 11-08-2007

Re: Raspberry pi lcd screen?

Community Veteran
Posts: 6,611
Thanks: 209
Fixes: 15
Registered: 16-02-2009

Re: Raspberry pi lcd screen?

Cheers guys, Thanks OJ after I posted it thought "I should have put that in hardware!"
Will give it a try later got some spare 10K pots.
Community Veteran
Posts: 6,611
Thanks: 209
Fixes: 15
Registered: 16-02-2009

Re: Raspberry pi lcd screen?

Worked great. Can now see the text from above.
Now to tidy the wiring up and start boxing the unit.
Community Veteran
Posts: 3,380
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Registered: 18-01-2013

Re: Raspberry pi lcd screen?

Now what you need to do is hook a thermistor up, read it with the Pi, generate a PWM stream based on the temperature read and a lookup table then smooth it with an RC network and feed it into Vee.
Works an absolute treat (I do this with PIC microcontrollers) - only of use if you're using the LCD in extreme temperature variances though Wink
Community Veteran
Posts: 6,611
Thanks: 209
Fixes: 15
Registered: 16-02-2009

Re: Raspberry pi lcd screen?

Since it is going to be an internet radio, I don't expect the temp to get above ambient (or <30C)
The joys of recycling eh? Tried painting the box this morning, put it outside to spray paint, left it to dry and it got blown halfway across the garden, so now to sand the grass off the top and start again  Cry
The box was one I got something off ebay in, it is just the right size and made of clear acrylic, have drilled the holes for the rotary encoders and the holding screws for the lcd on the top, and covered the lcd hole with masking tape to allow it to be clear when the rest is black.