Why are lcd numerals at an angle?
March 20, 2006 8:48 PM   Subscribe

Why are the lcd numerals in digital clocks and other such displays at an angle, as opposed to straight up-and-down?
posted by luftmensch to Technology (19 answers total)
 
Huh? What are you talking about?
posted by disillusioned at 9:03 PM on March 20, 2006


I just checked every digital clock in my house. They all display numerals straight up-and-down. There are plenty of clocks that display them at an angle, but I'd say that a vast majority do not. (I'm guessing a 90/10 split, but that's purely a guess.)

What makes you think that they're always at an angle?
posted by jdroth at 9:08 PM on March 20, 2006


Yes, every example listed by disillusioned has a 1 or 2 degree tilt. Some more than others. (those that are higher contrast tend to have less tilt, i see)

I would guess it is for readability and that "contemporary" look according to the 1980's designers who set the standard for those things. LCD displays tend to have less tilt than LED displays.
posted by clord at 9:10 PM on March 20, 2006


The digits that are at an angle (and, yes, I've seen them; they exist, but they're not everywhere) so you can tell that they're the right way around. It's so a 5 seen in a mirror is clearly a backwards 5 (because it's leaning left) and not a 2, which could lead to trouble if you're depending on a digital readout you're not sure the orientation of. Is it 05:52 or is it 52:20?

...Granted, I can't think of a lot of cases where you'd actually have a left-right mirrored view of a digital display, but this is the explanation I've heard for it. If anyone's seen the Futurama episode with the Giant Ball of Garbage, there's a gag with a similar premise to this (which I don't want to spoil because it's one of the best moments of the episode).
posted by wanderingmind at 9:16 PM on March 20, 2006


Even the least tilted display listed above has about 2 pixels of tilt. Could be camera tilt, hard to tell because the frame of the 'device' is cut off by the photo.

On preview: Yes! upside down clocks! perfect reason for tilt.
posted by clord at 9:20 PM on March 20, 2006


The Police's Ghost in the Machine album cover is a good example of the tilted LEDs.
posted by blueberry at 9:21 PM on March 20, 2006


For clocks in particular, if you have a pair of seven-segment displays with trailing decimal points, you can turn one of the displays upside down so that the two decimal points form a colon. The digits are simply slanted to match the angle of the colon. This technique was probably more important in the (expensive!) early days of LEDs, but I imagine that slanted numerals are still seen today mainly for aesthetic reasons.

When it comes to cheap consumer electronics, the design is determined by the engineer finding the cheapest manufacturing solution. It's the same reason that cheap alarm clocks all have the same horrible user interface.
posted by Galvatron at 9:31 PM on March 20, 2006


Yes! upside down clocks! perfect reason for tilt.

Er, well, turning tilted numerals upside-down will still leave them tilted in exactly the same direction. It was mirror reflection that was originally suggested, and that just seems odd to me.
posted by kindall at 9:32 PM on March 20, 2006


I always thought it was so the 7 looks like a 7.
posted by vacapinta at 9:36 PM on March 20, 2006


Picture's worth a thousand words:

seven segment displays
posted by Galvatron at 9:42 PM on March 20, 2006


One could argue that it's mostly done out of convention these days, as disillusioned's pictures demonstrate, most are not tilted that much any more, and most don't use the colon technique.
posted by delmoi at 10:57 PM on March 20, 2006


They might also be slanted so you can have simple straight conductor runs on the PCB from the connector to the display contact.
posted by scruss at 4:08 AM on March 21, 2006


Galvatron, that's utter bullshit. Mounting one of the displays upside down would add far more manufacturing costs than it saved.

Also, digital clocks never have the dots in a colon that far apart and the slant in your picture doesn't come to close to matching.

The simple answer is that perfectly upright digits are hard to read. Wikipedia concurs.
posted by cillit bang at 8:34 AM on March 21, 2006


More readable because slanting both increases the visual area of the numerals and makes the numbers appear closer together. Imagine if the numbers were upright: all the space above the decimal point would be wasted. This is true whether you are using LEDs or LCDs, assuming you need to have a decimal by every number.

Calculators need a floating decimal; clocks that flip them around for colons (if indeed any do) or use the same displays are possibly just hacks to save money.
posted by fleacircus at 11:22 AM on March 21, 2006


Galvatron, that's utter bullshit. Mounting one of the displays upside down would add far more manufacturing costs than it saved.

O RLY? Are you a hardware designer? This isn't rocket science, if you have something like a BCD to 7-segment decoder, you just have to swap some lines around to get an inverted display.


Also, digital clocks never have the dots in a colon that far apart and the slant in your picture doesn't come to close to matching.

I found the first reasonable match for "seven segment display" on google images, then spent two minutes making a mockup by duplicating and rotating. Sorry if I failed to meet your exacting standards.


The simple answer is that perfectly upright digits are hard to read. Wikipedia concurs.

Meh. Wikipedia is hardly authoritative, and that article doesn't even have references. If Horowitz and Hill says something about seven segment display readability, then I'll believe them.

fleacircus's suggestion that slanted numbers with decimals appear closer together is plausible.
posted by Galvatron at 2:17 PM on March 21, 2006


Are you a hardware designer?

Yes, actually. Are you?
posted by cillit bang at 6:39 PM on March 21, 2006


No, I'm not a hardware designer. But I still fail to see how manufacturing costs would be increased by flipping a display. Keep in mind the context: late 60s/early 70s vintage electronics, fabricated largely from discrete components with not a lot of ICs. Expensive LEDs.

I'm making no claim that people still do this today, with LEDs so cheap and all. I'm just suggesting an early motivation for designing slanted displays.
posted by Galvatron at 8:03 PM on March 21, 2006


Well if you're using discrete LEDs you can put them on the circuit board in any arrangement you like. From there you jump directly to multi-digit modules. There's absolutely no economic reason why using 4 single-digit modules for would be cheaper than directly sourcing a 4 digit clock module.

The problem with mounting some digits upside down is that instead of all being in a neat row, some digits will have their connectors at the opposite end to the others. That's going to severely complicate board design and assembly (this might not be a huge issue, but it's certainly not going to make things easier).

Is the turning a digit upside down thing purely conjecture on your part, or did you read it somewhere?
posted by cillit bang at 11:29 PM on March 21, 2006


There's absolutely no economic reason why using 4 single-digit modules for would be cheaper than directly sourcing a 4 digit clock module.

No argument there, but I'm betting you'd have a hard time finding one of those in, say, 1969. (Maybe I'm wrong, it's well before my time.)

Turning a digit upside down is not purely conjecture. Don't recall where I first ran across this, although you can still see it in hobbyist projects on the web.
posted by Galvatron at 6:46 AM on March 22, 2006


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