> At the bottom end, you have those silver ones they put in calculators.
> Usually a 7-segment one. I have a graphing calculator somewhere with a
> dot matrix LCD, but still silver, with no greyscale capability.
>
> I'm wondering... Is there a specific *name* for this type of LCD?

Passive matrix. As opposed to active matrix.

> What
> does it cost to put one of these into your product? Like, if you're
> buying a couple of thousand of those things, what's the unit price? How
> much circuitry does it take to drive it?

$1 would be my guess. You can probably find a bulk lot of 1000 on 
aliexpress or something. Regarding the electronics it's quite simple, 
just bang a voltage onto each segment you want "on", reverse the 
voltage, and then repeat very rapidly. The most important thing to 
remember with any LCD type is that the *time-average* voltage across any 
segment must be zero, or you will damage the LC material. If you've got 
a microcontroller or CPU already it should be easy to do in software.

> At the other end of the scale, you have the stupid-DPI full-colour
> back-lit LCDs with touch sensitivity that they put into every mobile
> phone, ever. What do *those* things cost? I'm guessing you need way,
> *way* more hardware to drive it. (An entire framebuffer, for starters...)

Price is roughly proportional to screen area (the factory doesn't care 
much how many screens it gets out of each "mother sheet"). For a 4" 
smartphone screen with touchpanel I'd say about $10. A laptop display 
could be $50. Really the price depends heavily on the volume, who the 
customer is, whether it is a custom design/off the shelf, what 
additional electronics/touch is included etc.

Yes you'll need some electronics to continually pump in the pixels. Most 
screens like that will use an LVDS interface, but you can get HDMI/DVI 
-> LVDS converters if your "system" already has those.

> I've heard it said that on "most" electronic devices, the buttons and
> lights are the most expensive part. As in, removing one button or one
> indicator light is a significant cost saving. So a toaster with three
> buttons is "much" more expensive to make than the same toaster with only
> two buttons. I'm not sure why this is; presumably because it's awkward
> to assemble a mechanical switch? (I.e., you have to have an extra step
> where a machine inserts all the moving parts into the right places.) I'd
> be interested if anybody has numbers.

In the world of very high volume mass production you can almost ignore 
tooling costs, so the cost is mostly made up of two parts: materials and 
assembly. A toaster might be a bit of bent steel with two plastic sides, 
you're talking $1 or so for those parts plus heating eleemnts, wiring 
and some screws, so maybe $10 total? A switch on the other hand is like 
a complicated mini-assembly in itself, so although the material cost is 
very low, there is a high assembly cost, so a switch could easily cost 
$1 too. So you've got a total cost of $13 or $14 depending on how many 
switches you use. If you're expecting to sell a million toasters, using 
one less switch will make you $1m more profit :-)

> I'm just wondering... High-colour LCDs are in even cheap phones now, so
> the LCD itself can't be all that expensive. So why don't more devices
> have these displays? For example, at the gym, the treadmill has a
> 7-segment LED display, and three buttons for cycling through the menues
> and selecting the option you want.

How many treadmills are they expecting to sell? If it takes an 
electronics engineer 12 months to design, prototype, test and debug the 
system, will it be worth it for them? Or would it be more profitable to 
just reuse the cheapo $5 LCD and board from the previous treadmill?

> I'm sorry, what was I talking about? Oh, yeah, LCDs. How come (for
> example) my washing machine doesn't have one? I've only ever seen them
> on the most expensive ultra-luxury models. Surely this stuff isn't
> actually that expensive to manufacture anymore?

How much profit do you think the manufacturer makes on a cheap washing 
machine? Even if there were zero development costs, is it even worth 
them spending an extra $10 on a high res screen with touch panel?

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