Hello I am designing a logic circuit where the inputs are some switches and also some digital inputs are needed, below is an example of the circuit used to enhance the switches as digital inputs.  

I am trying to add a pull down resistor for two digital lines which are the remaining inputs for the logic circuit.

Considering that when the digital input signal is not wired, the logic circuit needs to see 0v, How can I replicate this behavior for a digital input signal?

I thought of a pull down resistor, but as I don't know the output impedance of the circuit driving the input of the logic gate, how can I come up with a good value for the pulldown resistor?

I am designing a logic circuit where the inputs are some switches and also some digital inputs are needed, below is an example of the circuit used to enhance the switches as digital inputs. 

I am trying to add a pull down resistor for two digital lines which are the remaining inputs for the logic circuit.

Considering that when the digital input signal is not wired, the logic circuit needs to see 0V, How can I replicate this behavior for a digital input signal?

I thought of a pull down resistor, but as I don't know the output impedance of the circuit driving the input of the logic gate, how can I come up with a good value for the pulldown resistor?

Hello I am designing a logic circuit where the inputs are some switches and also some digital inputs are needed, below is an example of the circuit used to enhance the switches as digital inputs.

Considering that when the digital input signal is not wired, the logic circuit needs to see 0v, How can I replicate this behavior for a digital input signal?

I thought of a pull down resistor, but as I don't know the output impedance of the circuit driving the input of the logic gate, how can I come up with a good value for the pulldown resistor?

Hello I am designing a logic circuit where the inputs are some switches and also some digital inputs are needed, below is an example of the circuit used to enhance the switches as digital inputs.

I am trying to add a pull down resistor for two digital lines which are the remaining inputs for the logic circuit.

Considering that when the digital input signal is not wired, the logic circuit needs to see 0v, How can I replicate this behavior for a digital input signal?

I thought of a pull down resistor, but as I don't know the output impedance of the circuit driving the input of the logic gate, how can I come up with a good value for the pulldown resistor?