Hi, I've been working on getting a water flow sensor connected to my Raspberry Pi. It's a simple hall effect sensor that sends 5v pulses to indicate the rate of water flowing.
So I tried to use a voltage divider to reduce the 5v to about 3v. I got this to work fairly easily as a stand alone circuit. But when I connect it to the pi, the voltage changes. What should be a 3v pulse now reads around 1v. I think the problem is the internal pull down resistor? I thought these could usually be ignored because they are very weak?
I finally got it work by using a 10k pot as the voltage divider. Then I was able to easily manually the voltage while the device was connected (and sending HIGH signal) so that 3v ends up on the GPIO pin. Is this a good solution? Am I missing something? When I read about connecting 5v devices to the pi a voltage divider was often recommended. Maybe I should be disabling the internal pull down resistor somehow? I am using the npm onoff library which does not support changing the internal pull up/down resistors. I tried adding a pull up resistor, but then the sensor could not pull the signal LOW.
Thanks.
So I tried to use a voltage divider to reduce the 5v to about 3v. I got this to work fairly easily as a stand alone circuit. But when I connect it to the pi, the voltage changes. What should be a 3v pulse now reads around 1v. I think the problem is the internal pull down resistor? I thought these could usually be ignored because they are very weak?
I finally got it work by using a 10k pot as the voltage divider. Then I was able to easily manually the voltage while the device was connected (and sending HIGH signal) so that 3v ends up on the GPIO pin. Is this a good solution? Am I missing something? When I read about connecting 5v devices to the pi a voltage divider was often recommended. Maybe I should be disabling the internal pull down resistor somehow? I am using the npm onoff library which does not support changing the internal pull up/down resistors. I tried adding a pull up resistor, but then the sensor could not pull the signal LOW.
Thanks.