In my project I am using arduino mega. I need 120 output pins for my project . These pins are going to mosfet for turning on/off electromagnets. As arduino mega is not having 120 output pins I thought of using 74HC595 shift register. But still I need to use 15 shift registers(74HC595). Is there any alternative method for getting 120 output in arduino.
If your solenoids are small (<150mA), then you could use the TPIC6B595 (ebay).
This chip is the same as a 74HC595, but with buildin mosfets.
Why a Mega. 15 shift registers only use three Arduino pins.
Alternative can be 8 times a MCP23017.
WaWa, I think that Aswin2017 already has the Mega for whatever reason; maybe the expansion from e.g. 40 to 120 outputs was an after-thought. Or maybe the design was not thought through before buying the Mega ;)