Can you use diodes instead of OR gate?
There is a really cool trick that you can use under specific conditions that allows you to build a 2-input OR gate or AND gate using only 1 diode and 1 resistor.

The conditions are:

1) The circuit is low speed.

2) The load impedance is high, such as a CMOS input.







simulate this circuit &ndash; Schematic created using CircuitLab

This can be expanded to as many inputs as needed by adding more diodes.