7segmentdisplaylcd
I can find a number of LCD TN 8 digit 7 segment displays but they are far to big. The kind of size I'm looking for is the ones you usually find in mini calculators.
The size im looking for is around 10mm by 50mm. The smaller the better really. The other specs of the LCD are not really important at this time other than getting the smallest possible. Maybe I'm wrong in my search for an TN LCD?
Any help is greatly appreciated.
Thanks
Scott
It's a 7-segments display. Unlike the dot-matrix character displays kevlar refers to these are most often not intelligent module. Most dot matrix displays have an HD44780-compatible controller which you simply can write ASCII codes to, but a 7-segment LCD will often be just the glass, with connections for segments and a number of backplanes (often up to 4).
Driving LCDs can be awkward since they don't use just two levels, so you can't drive them with common digital logic.
The best thing you can do is select a microcontroller with integrated LCD controller, which you can connect the display directly to, like the TI MSP430x4xx. Like most controllers this one also knows just segments; it isn't aware of digits or anything. (Great, first we had a dumb display, now we have a dumb driver as well!) There's reason for this. These LCD drivers are often used to drive custom LCDs which may be a mix of a numeric part, bar graphs and custom symbols. Such a symbol is also a single segment, so it makes no sense to talk about digits.
This display has symbols like "battery" and "alarm clock", but also all text fields, like "AM", "PM" and "SNOOZE" are symbols consisting of a single segment (i.e. controlled by a single bit).
Further reading
MSP430x4xx Family User's Guide. LCD controller is covered on p.709 ff.
I haven't coded in VHDL in a long time -- I don't know why they still teach it, they should teach Verilog -- but the answer below still applies.
Your counter needs to have the following inputs:
Your controller takes in 4 button inputs and generates 3 outputs. For buttons 3 and 4 it detects a rising edge of the input and generates a pulse for 1 clock cycle, i.e.
____ ____ ____ ____
clock: __| |____| |____| |____| |
____________________
input: _______| |_____
____
output: __________| |__________________
The "counter enable" output of the controller is controlled by buttons 1 & 2. A rising edge on button 1 sets it high and a rising edge on button 2 clears it to low. In effect the counter enable is controlled by an SR latch where the S signal is button 1 and R is button 2.
You then connect the 3 outputs of the controller to your counter (Problem 2).
Best Answer
The Densitron DG-067 package is 38 mm wide x 15.2 mm high. The viewing area is 34 mm x 12.1 mm. The characters are 6 mm (1/4") high.
BTW the datasheet doesn't mention TN, but this page where it is listed is titled "LCD Glass, Segmented Glass, TN Glass"