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I'm looking for one of those small numeric LCDs used on OTP authentication keys (the one your bank gives you to access their website, to be clear).

All LCDs I find on the various manufacturer's sites are those big 20x2 alphanumeric displays... I need something that can be fitted on a USB key. (note: it doesn't strictly have to be numeric-only, it could even be a graphical LCD for all I care...)

Any suggestions?

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  • \$\begingroup\$ Did you search Digikey? search.digikey.com/scripts/DkSearch/… \$\endgroup\$
    – kenny
    Jul 3, 2011 at 10:03
  • \$\begingroup\$ @kenny the only parts small enough are 3 digits displays. no good. \$\endgroup\$
    – CAFxX
    Jul 3, 2011 at 17:17
  • \$\begingroup\$ Two good things you can add to this Question: The number of digits you'd like to display, and A numerical estimate of the maximum dimensions for the LCD you can tolerate. \$\endgroup\$
    – boardbite
    Aug 27, 2012 at 18:48

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Since you're looking for something with only a few digits, you don't need it to have its own controller. Try looking for LCDs called "bare glass". Those are just the LCD with the segments brought out to pins or contacts intended for zebra strip connectors.

If you use one of these, you will have to drive it yourself. It's not like a LED display where each segment is turned on to display it and off to not. LCD segments are driven with AC, and must not experience any net DC. Fortunately there are various microcontrollers that have such LCD drivers built in. For example, Microchip usually puts a "9" near the end of the PIC model number to indicate the LCD driver. Once you set up the LCD driver peripheral, you get a bunch of bits in memory that you can set or clear that directly map to LCD segments being displayed or not. The 7-segment generation if you want to display numeric digits is up to you.

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  • \$\begingroup\$ I'm not so fond of these "bare Glass" LCD, but that's for mechanical reasons. They usually connect to the PCB via a strip of conductive rubber, which means that the enclosure has to keep both together. That's nice if your design is for a 10k/year production, where you can afford a custom enclosure, but not as handy for DIY. (Maybe I'm, next to being clumsy, also too demanding about the finishing of my design :-)) \$\endgroup\$
    – stevenvh
    Jul 3, 2011 at 15:40
  • \$\begingroup\$ @stevenvh: I have some bare glass 7-segment LCD displays that have pins, which are easy to connect to. Those tend to be the physically bigger ones. If the op wants something small, he's probably stuck with zebra strip connectors. I don't like them much either, but there is probably little choice in very small displays. \$\endgroup\$
    – Olin Lathrop
    Jul 3, 2011 at 20:55
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    \$\begingroup\$ Usually, the bare glass and elastomer contacts are kept together by a metal frame that mounts to the PCB with bending tabs in slots. Honestly, this is the only kind of structure that will fit your mechanical constraints. You need to look for a microcontroller with a USB device port and LCD driver interface. Atmel's AVR series have either one or the other, but not both. The smallest Atmel device I can find with both is the SAM9RL64, an ARM9-based chip in 217 BGA. \$\endgroup\$
    – Mike DeSimone
    Jul 4, 2011 at 3:43
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I'm a little late, but if you're still looking, here's one I use:

enter image description here

Disclosure: I'm not the manufacturer of the LCD, but I buy them in quantity and sell some on my website to make them a little more affordable for small quantities.

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    \$\begingroup\$ For a good find it's OK to be "a little" late :-) \$\endgroup\$
    – stevenvh
    Aug 27, 2012 at 18:29

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