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Printer Port 256 Relays 16K Dot Matrix - del20021


Using this circuit on Printer Port, one could drive 256 Relays or 16K LEDs as Dot Matrix display. Home Automation output module of many Relays or Lamps.

It can be used to drive a Large size multiplexed LED dot matrix display or Latched Relay-Solenoid-Motor-Lamp Array Drivers. 

SCADA System - Project Idea

This circuit can be modified for a Static drive output or a fast changing output like a Waveform Generator. You can also make it a 16 Bit waveform generator. The frequency limited to the speed of the port or a fraction of it, depending on 8bit, 16bit or 32bit.

Now I have Some Explaining to do. Latch the U7 with a 8 Bit Data to address the device you want to talk to. So one among the 32 Output Devices can be Selected by a combination of G1-G2 of U5-U8 and U7 8 Bits, Split into Two Nibbles for Upper and Lower 16 Devices. That means 16 * 2 = 32 Devices of 1 Byte each,. 32 * 8 = 256 if my calculations are correct. Please verify.

Printer Port 256 Relays 16K
                          Dot Matrix - del20021
PNG-Schematic     PDF-Circuit     DSN-Source
Printer Port 256 Relays 16K Dot Matrix - del20021
To view circuit click the Link of PNG or PDF, The PNG Image can be Drag Scrolled with Mouse. .

One of the decoders U5 or U8 decode their respective nibble and output a Low on Selected device to Latch Data on the Chosen one (74HCT373). Why HCT ?  Speed is good, low power and CMOS ! and works with TTL too. It Interfaced well for me on a Card with Both TTL and CMOS levels, with a Fast uC.

The 74HCT373 outputs are current amplified and isolated by darlingtons and optoisolators. Both source and sink  examples shown.This circuit was not tested and documented properly. So there may be things missing. It is just a Concept design.

Home Automation by Edward Cheung

Use it, as it is to drive 256 LEDs, Relays or Outputs, as a 128*128 matrix it can drive 16,384 LEDs dot matrix display in Multiplexed mode. Modifications over this circuit, can expand it to any number of outputs, but more outputs means, the speed of data will reduce. Shown in circuit for only 16 LEDs, Duplicate like that for as many as you want, upto 32  74HCT373 need to be used. then you have 32 * 8 outputs.

The design source is here 20021.zip. Connect to printer port with a good quality shielded cable.