Controlling LED with parallel ports

[nasirasim]

Hello, if anybody know how to control 100 LED with one parallel ports. if any body have an idea please tell me. Thanks

 

[kukitron]

Hello,

Depending how you want to control them,

If you want to control them individually, then you need to use buffers and a microcontroller to manage each individual led.
Control those LED's as if you were accesing an hexadecimal memory location,

Each address would belong to each LED, such as 00 to 1, 01h to 2, etc,

For that, you will need a converter from Hex to linear, and those are available

Cheers,

 

[bilgekaan]

you need to use IO expanders. parallel port does not have enough IO ports.

philips and maxim has I2C or SPI interfaced io expanders, one of maxim ic has 28 IO. Four of them on an I2C line solves your problem yuo dont need to use any other microcontroller.
but parallel port has no open collector input so you must connect I2c parallel port adapther between paralel port and io expanders.

adapther is a small circuit made of some resistors and hex inverter( for intances 74LS05 ) you can find schematic of it in the www.in the PC side you must

implement I2c or SPI protocol to drive leds through adapther and expanders .

 

[Frank32]

You may use serially connected demultiplexors and latches for saving state of leds (all of inputs first demultiplexor connected to LTP, one of inputs next demult. connected to output of previous etc.) after transmit by LTP any byte one of the leds change his state. This method requre ~20 74xxx ICs for 100 LEDs. Or ~10 new ~52 pin TI ICs.

For control 100 LEDs you need >100 pins and this is main limitation.

 

[Kaleem]

You should be able to do so using a 7-128 line decoder.

------------------
LTP -> decoder inputs | 7-128 decoder |decoder outputs -> LED's
------------------

 

[rkodaira]

I would use a microcontroller with enough I/O ports, for example the PIC 18F452, which has 34 I/O ports. Eight ports are dedicated to parallel slave port that can be connected to PC parallel port and the remaining ports used to drive the leds.
With a 10x10 matrix (10 I/O ports x 10 I/O ports), you can address each led by a scanning/multiplexing software and the leds can be toggled on and off by sending the address via parallel port. Simple hardware (no decoders or buffers) just add some resistors to limit current to leds (in fact PICs I/O can drain or source a maximum of 25mA per port or 200mA for all ports, enough to drive the led matrix). The problem is that you need to know how to program the microcontroller (but it is no hard at all).

 

[Nick C.]

Depending on what you want to do with these LED's,
I would agree that addressing them in a matrix might
be the way to go. Or you could always go with several
cascaded SIPO shift registers, such as the 74HC595, but
the wiring alone would be a nightmare. :roll:

Yet another alternative might be a pair of MAX7221's.
That will give you control over 128 LED's with a bit of
clever programming.

Good luck with your project.

Nick