hanzhong
Newbie
Hi expert,
Info:
The pulse signal is 12V to 0V (normally condition it's 12V and whenever there's pulse it'll be 0V for 50 milliseconds). I try to read a pulse based signal (which you can consider it V4 and V5 as per image in attachment) from external circuit into my microcontroller through NPN transistor (which act like a level shifter).
For the circuit which base resistor is 330 ohm, I discover pulse voltage drop to 0.6V. However when I change to base resistor to 470k ohm, pulse voltage is at 8V which allow me to read the pulse signal at transistor output.
Can you provide me any explanation why such behavior occur? The cause of voltage drop perhaps? Because as far I know base resistor is fine to be small value, as long as it does not exceed maximum rating of base current. Please share me your thought about it.
Info:
The pulse signal is 12V to 0V (normally condition it's 12V and whenever there's pulse it'll be 0V for 50 milliseconds). I try to read a pulse based signal (which you can consider it V4 and V5 as per image in attachment) from external circuit into my microcontroller through NPN transistor (which act like a level shifter).
For the circuit which base resistor is 330 ohm, I discover pulse voltage drop to 0.6V. However when I change to base resistor to 470k ohm, pulse voltage is at 8V which allow me to read the pulse signal at transistor output.
Can you provide me any explanation why such behavior occur? The cause of voltage drop perhaps? Because as far I know base resistor is fine to be small value, as long as it does not exceed maximum rating of base current. Please share me your thought about it.