Serial LCD with shift register - Increase outputs

Hello Dear friends,

I am using the instructions provided here http://www.instructables.com/id/Hookup-a-16-pin-HD44780-LCD-to-an-Arduino-in-6-sec/ to build myself a serial LCD using a shift register.

Everything works as it should, but since I would like to have more outputs I heard I could add more shift registers to this one and double the number of outputs.

So lets say I want to drive an LCD, as I am now, but I want to add more shift registers to enable a few relays without using the digital pins on the Uno. Would this be possible? If so would I need a specific library?

amvcs08:
Hello Dear friends,

I am using the instructions provided here http://www.instructables.com/id/Hookup-a-16-pin-HD44780-LCD-to-an-Arduino-in-6-sec/ to build myself a serial LCD using a shift register.

Everything works as it should, but since I would like to have more outputs I heard I could add more shift registers to this one and double the number of outputs.

So lets say I want to drive an LCD, as I am now, but I want to add more shift registers to enable a few relays without using the digital pins on the Uno. Would this be possible? If so would I need a specific library?

I'm kinda confused. You want to control relays with shift registers? That is possible and without library, just some coding.
"without using the digital pins on the UNO" what do you mean? to control relays you have to use digital pins, 3 digital pins with shift register can control 8 relays if I'm correct.

By the way, maybe I2C LCD may be of your interest. Only 2 digital pins to drive LCD.

Or serial LCD (tx and rx pins)

I already have the shift register set up for the LCD, so in practice I won't use any additional pins for the attached relays.

Well, it is possible but there are a few complications.

To control relays, use a TPIC6B595 which is capable of driving them directly, very neat.

The problem is - you are (presumably) using a library to control the LCD whereas to use two (or more) shift registers, you have to re-load all of them (with the same values for those you do not wish to change) every time you want to modify any of them, so you can no longer use the library - you have to write your own.

Even if you were to use separate latch control for the shift registers, the library would resist your control of the data and shift lines.

So if you can get around the library matter, go ahead!