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Topic: LCD shield and/or LCD serial backpack (Read 34 times) previous topic - next topic

mem

kuk, es gibt kein problem  :)


cheater, I have 3 or 4 LCDs in my parts box and wonder if its worth testing the contrast and backlight circuits on them using my arduino. If you want to modify the transistor driver code so it works with the arduino's  timers running on a 16mhz clock then I would be happy to test this on my breadboard.

I don't need the code for the LCD data for this test but would be happy to look at that if it would help you.

Cheater

Thanks mem. I'd love it if you could test PWM with a 0.1uf capacitor on the contrast.
I'd do it but I dont seem to have any transistors around. I could scrounge one....

No code yet. I'll whip it up once I get the PCBs. :)
Just test with AnalogWrite for now.

I've created a Sourceforge project for this to keep everything nice and tidy.
I'll be setting it up today.

Cheater

Just tested (very roughly) without a transistor and it seems that the contrast acts just like a normal LED.
Ripple isnt a problem. A 0.1uf capacitor should just smooth things out a bit though.

Ok last questions:
Is a resistor required on the LCD's backlight? Sparkfun doesnt use one. I'd imagine it would be fine.
And is a resistor required on the transistor's base? I wouldnt think so.

I will be rather happy if I can ditch two resistors. :)
I'll then be able to order.

Current parts list (assuming I can ditch two resistors):
2x 0.1uf 0805 capacitor
2x BC817 SMD NPN transistor (0.8A max)
1x 10k 0805 resistor
1x ATmega8 QTFP

Cheater

My bad. The ATmega8 doesnt have enough PWM and I forgot about slave select. :)
I've now got it with a ATmega168 which has more PWM and more space which should be good.

Cheater

Just a update: I have the OpenLCD website up.
http://openlcd.sourceforge.net/

Eagle files (completely different to whats posted above) are in SF's release system.
http://sourceforge.net/project/showfiles.php?group_id=217002

Can someone do a quick check on the circuit to make sure it will work before I order a large stack of them?
I figured that its only slightly more to get ~138 of them as it is to get 25 of them so why not.
I dont want that many coasters though. ;)

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