How many displays on one device?

Hi how many 1 or 2 digit Displays for Numbers (7-elements or LCD) can I connect to an arduino based device and address with individual data output?

it depends on your display(s) (exactly type?)! for my 1602A LCD (16 columns, 2 rows) i'll need 3PWM and 3 DigitilOuts. So i could connect two of them to my uno.

newuino: Hi how many 1 or 2 digit Displays for Numbers (7-elements or LCD) can I connect to an arduino based device and address with individual data output?

If you use external chips, something like the MAX7219/MAX7221 that can drive 8x 7 segment displays per chip (and you can daisy chain multiple chips together) and only use a total of 3 data pins on the arduino for all the chips.

With various interface technologies you could have many displays. Consider I2C-interface LCD modules, you could have eight or more with units that allow a custom I2C bus address.

For 7-segment LED displays, the answer to your question depends on on what additional hardware you are prepared to use:

  • If you don't want to use any external hardware apart from series resistors, then you are limited by the number of output pins. For example, you could drive 2 digits using 14 outputs pins (7 per digit, or 8 if you want to drive the decimal points). At a push, you could use 2 x 2 multiplexing to drive 4 digits using 14 pins. More than 2 digits is not advisable because of the 40mA absolute maximum output current rating of Arduino output pins.

  • If you are prepared to use 1 transistor per digit to avoid the 40mA limitation, you can multiplex 4 digits easily (using 7 + 4 output pins), or 8 at a push (using 7 + 8 output pins).

  • If you are prepared to use external ICs then there is no limit to the number of digits you can drive from an Arduino.

... for my 1602A LCD (16 columns, 2 rows) i'll need 3PWM and 3 DigitilOuts. So i could connect two of them to my uno.

Huh???

Don

My 1602 uses 6 pins 4 for data, one for RS and 1 for E (enable). It is possible to reuse all pins and just have each LCD with its own E pin then just toggle the pin of the LCD you want to write to. So 6 pins = 1 display 7 = 2, 8 = 3 so on and so forth. Obviously if you are controlling contrast and brightness by software then you will need 2 pwms for each display too.

My 1602 uses 6 pins 4 for data, one for RS and 1 for E (enable). It is possible to reuse all pins and just have each LCD with its own E pin then just toggle the pin of the LCD you want to write to. So 6 pins = 1 display 7 = 2, 8 = 3 so on and so forth.

This was discussed a few days ago here: http://arduino.cc/forum/index.php/topic,118053.0.html

Don