RGB backlight negative LCD 20x4

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k5map
 
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RGB backlight negative LCD 20x4

Post by k5map »

I just wired up my new RGB backlight negative LCD 20x4 (Product ID: 498). Its working great for Blue & Green but Red is not showing up at all. Is the Red colored controlled solely via pin 16 (-R) on the LCD?

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adafruit_support_bill
 
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Re: RGB backlight negative LCD 20x4

Post by adafruit_support_bill »

That is correct. If you connect a jumper from pin 16 to GND, does it light up?

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k5map
 
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Re: RGB backlight negative LCD 20x4

Post by k5map »

The LCD does light up but no change in the color (not showing Red). I did notice as soon as I apply power to the display, it shows a Green background. And when Red or Yellow are shown using the example Python script, it shows the text in Green. Blue and Green text do show up in the correct color.

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adafruit_support_bill
 
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Re: RGB backlight negative LCD 20x4

Post by adafruit_support_bill »

Sounds like a defective backlight module. Please contact [email protected] with a link to this thread and we can replace the display.

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rbbtebo
 
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Re: RGB backlight negative LCD 20x4

Post by rbbtebo »

Good morning, Adafruit!

I'm about to hook up a 20 x 4 RGB LCD. In reading the tutorial, it shows Pin 15 going to +5V. However, it reading old posts, I saw a post by adafruit support - Rick on 3/15/11 that says pin 15 should go to ground....

I'm confused and don't want to burn things up. Help! - Which do I hook Pin 15 up to?

Also, I'll be driving it with a PRO Trinket. My understanding is that the PRO should work like a UNO.... I saw some posts referring to standard Trinket and special libraries needed.... For the PRO Trinket - can I just use the standard libraries?

Thanks always for your help!
Balad

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rbbtebo
 
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Re: RGB backlight negative LCD 20x4

Post by rbbtebo »

Also - do I need current limiting resistor for the LED?

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adafruit_support_bill
 
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Re: RGB backlight negative LCD 20x4

Post by adafruit_support_bill »

Pin 15 is the 'common anode' and should be connected to +5v. Pins 16, 17 & 18 are the R, G and B cathodes. These already have current limiting resistors on board.

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rbbtebo
 
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Re: RGB backlight negative LCD 20x4

Post by rbbtebo »

Awesome, Bill. Thank you as always.

Will I have any problems using the PRO Trinket?

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adafruit_support_bill
 
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Re: RGB backlight negative LCD 20x4

Post by adafruit_support_bill »

Sorry, I missed the second half of your question.

You should not have any problems with the Pro Trinket. It has the same Atmega328 processor as an UNO. Other than a couple of pins reserved for the USB interface, it performs pretty much like a standard UNO.

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rbbtebo
 
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Re: RGB backlight negative LCD 20x4

Post by rbbtebo »

Bill - you rock as always! Thank you and have a great weekend.

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