I need a small LCD display for a digital thermometer-like device I am making. I need to be able to display 6 digits or letters only.The main constraint is the small size and rectangular shape.I cant have width more than a little over a centimeter and length appropriate for 6 characters. I am unable to figure out how and where I can get this type of LCD. I am also ok with other displays, e.g. LED-based.
LCD/display for a digital thermometer-like device
displaylcd
Related Solutions
Hmmm. I'll assume that you mean an LED display.
If you are wanting to display a full character set, you might want to consider using several 5x7 led matrix. See http://www.best-microcontroller-projects.com/led-dot-matrix-display.html for an introduction. MAX7221 driver chips can be used to instead of multiplexing the rows and columns. While the extra chip does add to the parts costs, it will mean bright letters and less pins being used.
Give the dimension of the display that you are after, you'd need to find a LED matrix which contains 10mm LEDs.
I don't see this as a cheap project by the time you assemble the LED matrix displays. Good luck as it sounds like fun.
The problem with using a microcontroller to drive an LCD is that an LCD requires constant attention. This can be mitigated with a CPLD driven over SPI (using DMA, of course), but then you run into the other problem: Color LCDs require a lot of data. 320x240 in black and white is marginal at 9.6KB, but make it 24 bit color and suddenly you need to deliver 230KB of data in 1/60th of a second. (Don't forget, though, that you can get 4-bit, 16-color control just by tieing the low 20 bits to one setting). A 24-bit frame buffer no longer fits in onboard RAM on most microcontrollers, and you probably don't have time to read from an external RAM chip, clock the data out, and still do other processing. Trying to do this with a CPLD (or an FPGA) and a RAM chip gets you well over the $2 price that caused you to balk in your question.
The traditional solution to interfacing a microcontroller with a color LCD is a display controller like an SSD1963. Here's a very simple block diagram:
Parallel input to a big RAM frame buffer (Translation: More than $2) interfaced with a register-configurable parallel LCD interface. The parallel input is usually compatible with a memory bus interface.
The color LCD market is not always easy to find on the web, usually being the domain of OEMs only, with the rest buying displays from companies who integrate the controller with the display. The best resource I've found has been Crystal Fontz, specifically this page on choosing graphic LCDs. Scroll to the bottom for the controllers, which include the following options (note: Not all are color controllers):
- Epson S1D13521B01 E Ink Broadsheet (1 module)
- Epson S1D13700 (11 modules)
- Epson SED1520 Compatible (8 modules)
- Himax HX8345 Compatible (1 module)
- ILITek ILI9325 Compatible (3 modules)
- KS0107/KS0108 Compatible (26 modules)
- Novatek NT7534 (14 modules)
- Orise Technology OTM2201A (1 module)
- Orise Technology SPFD5420A (1 module)
- RAiO RA8835 (1 module)
- Sanyo LC7981 (13 modules)
- Sino Wealth SH1101A (2 modules)
- Sitronix ST7920 (29 modules)
- Solomon SSD1303 (1 module)
- Solomon SSD1305 (9 modules)
- Solomon SSD1325 (2 modules)
- Solomon SSD1332 (1 module)
- Solomon SSD2119 (2 modules)
- ST STV8105 (1 module)
- Toshiba T6963 (23 modules)
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Best Answer
The smallest standard product LCD glass I could find is one from Varitronix that is 20.3mm x 38mm. It offers eight digits instead of 6. According to the data sheet for this part it is available with pins attached which adds a very small amount of additional width.
Note that for smaller sizes it is generally required to work with a vendor such as this to get a custom LCD glass made to your size requirements. Smallest size will generally imply that you use zebra strip for connections and a custom tooled case / holder to bring the display into proper contact and orientation with the circuit board. Do note that for small form factor displays it is common that the digit height is approximately one third the overall width of the LCD glass with the rest being used up by the contacts and sealing area.