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Forum Index : Microcontroller and PC projects : Programmable calculator on Pico DIY

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dddns
Guru

Joined: 20/09/2024
Location: Germany
Posts: 515

Posted: 06:58am 08 Jul 2025

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Maybe the good old "Nokia" display could be an option as it IIRC does not need to be backlit in daylight and could display graphs, but I really don't know its specs and power consumption.

Nice work!
Best wishes

zeitfest
Guru

Joined: 31/07/2019
Location: Australia
Posts: 575

Posted: 02:01pm 08 Jul 2025

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Quote In case the whole LCD can work from 3V3 you can remove the 5V

I did try running the (old) lcd on the 3.3v, but there was no visible output.
Some modules will display OK on the 3.3v apparently but others not. The backlight
led is ok on 3.3v, and the processing might run, but the glass logic levels need
more juice.

Frank N. Furter
Guru

Joined: 28/05/2012
Location: Germany
Posts: 947

Posted: 06:28am 09 Jul 2025

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@zeitfest:

Are you sure that it is not due to the negative contrast voltage? I had the same problem. It worked with this circuit here:
https://elm-chan.org/docs/lcd/lcd3v.html

I have realised the PWM with the Picomite and can now set the contrast via the duty cycle (or was it the frequency?

).
In any case, the display didn't show anything at all before with 3V3, now it works...

Frank
Edited 2025-07-09 18:09 by Frank N. Furter

zeitfest
Guru

Joined: 31/07/2019
Location: Australia
Posts: 575

Posted: 11:46am 10 Jul 2025

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Quote PWM with the Picomite..

That looks like the best solution

.
Though, as it turns out I can get ridiculously cheap boost modules and the 5v will be useful for future growth so that's the way for now.

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