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I am using an LCD-S2X1C50TR and direct driving it with a PSoC 4200 Microcontroller. I was testing my circuit by viewing the LCD at an angle and it looked fine. Until I put my eyes directly above it, do I notice that the contrast is terrible and difficult to read.

Things I Noticed: Bringing up the supply voltage from 3V to ~4V obviously made it better, but I was curious on why it's behaving this way. The device is rated 3V~5V on DigiKey, yet at 3V, it's only visible with a side view.

Edit: I suppose DigiKey just screwed me over. Upon looking at it with other suppliers, they state a 5V supply voltage and nothing less. There was a revision to the LCD made by the company that Digikey didn't happen to update on their end. Lesson learned.

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  • \$\begingroup\$ sounds normal, it's an analog display. what the issue? \$\endgroup\$ – dandavis Mar 27 '18 at 20:11
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    \$\begingroup\$ It's rated with a minimum of 3V, but it isn't visible at 3V. Am I doing something wrong? Should my end product just tilt the LCD for users? \$\endgroup\$ – Dmitriy Mar 27 '18 at 20:12
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The device is rated 3V~5V on DigiKey [...] I suppose DigiKey just screwed me over. Upon looking at it with other suppliers, they state a 5V supply voltage and nothing less.

I found a supplier linking Rev B of the display datasheet which does mention 3V - 5V, as well as another linking Rev C of the display datasheet which mentions only 5V.

So Digikey didn't make it up - at one time, the claimed specification was 3V - 5V. It looks like the manufacturer changed the specification (for the worse) while keeping the same part number!

If I was in your position, I would contact the manufacturer (Lumex) and ask:

  • What are the markings on that display model, to identify whether datasheet Rev B (with its 3V - 5V AC specification) or Rev C (with its 5V AC specification) applies?

  • What are the differences between a Rev B and a Rev C display?

    According to the Rev C datasheet, ECN# 11903 (applied in 2014) seems to be the difference between the Rev B datasheet which mentions 3V minimum and the Rev C datasheet which mentions 5V minimum. I expect that this ECN# would be part of the discussion.

  • Can a Rev C display (which you may have, based on your symptom) be used with acceptable contrast at 3V and, if so, how?

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LCDs are built with an "angle of view" specified in the datasheet. This is the optimum viewing angle, and it's determined by the orientation in which the LCD glass is put in the frame and, more importantly, by the way the glass is ground prior to laminating the LCD together.

If you need to be able to see the LCD from a different angle, flip or rotate it physically, and then counter-rotate the graphics in your firmware/software. If this isn't possible, order a different LCD or accept it as a learning experience.

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  • \$\begingroup\$ Optimal viewing for that LCD stated was 6 O'clock, well okay it viewed nicely at 6 O'clock, but not perpendicular to the display. It is common for LCDs to not be visible at a perpendicular angle to the display? Should I go searching for an LCD that states 'perpendicular visibility'? \$\endgroup\$ – Dmitriy Mar 27 '18 at 21:00
  • \$\begingroup\$ The manufacturer's assumption is that, because LCDs have an optimum viewing angle in the first place, a product is designed with a screen that will always be slightly higher (bus depot sign) or lower (home stereo display) or to the right or left of the viewer (automotive dashboard displays). It's unlikely that the user is always looking at the screen head-on, so perpendicular viewing is not commonly available, though it does exist. \$\endgroup\$ – schadjo Mar 27 '18 at 21:07

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