Newbie anomaly

[taavi889]

Hello! I have a little anomaly which I cant find answer for. I designed a negative trigger circuit to detect car door switching:

In this circuit, bothers me the most example 2. How is this possible that before the diode voltage can be smaller than after, considering the pull up to +5V?
As i know current flows from higher potential to lower. Considering the 2V at the cathode, at the anode should be 2.3V, but in reality, voltage is smaller, how is this possible?. I dont know what kind of circuit is behind the question mark.

 

[Alec_t]

Welcome to EP.

How is this possible that before the diode voltage can be smaller than after, considering the pull up to +5V?

The MCU is pulling the voltage down to 1V.

Considering the 2V at the cathode, at the anode should be 2.3V,

No. It would be 2.3V only if the diode were conducting (which it isn't, because the cathode voltage is higher than the anode voltage).

 

[taavi889]

Hello, thank You for answering.

The MCU is pulling the voltage down to 1V.

How isn't the MCU pulling the voltage down in example 1, when the wire is unconnected?

No. It would be 2.3V only if the diode were conducting (which it isn't, because the cathode voltage is higher than the anode voltage).

Actually the diode is conducting and current is flowing in the direction shown, also I forgot to mention that the voltage behind the question mark was about 1.5V before i connected my circuit to it, so my circuit is pulling the whole system up to 2V, which is expected.

 

[taavi889]

Problem solved, there was actually voltage switching.