u/SOLID-DevMan

Hello, as the title says is it possible to do?

More details

I'm building a primitive water level sensor to use with my nodemcu,

I don't have access to a lot of the sensors I did try to get an ultrasonic sensor which was very very bad so after some researching I found the best way is just to get a PPR pipe which is locally available and stick a bunch of graphite rods in it

But I ran into an issue where I wanted some resolution for the level sensing so I put eight levels but the node MCU doesn't support that many pins so I thought of a good idea for multiplexing since I don't have access to an I2C board to expand the pin number

The idea was that the top level probes would be connected directly to the pins and the lower level probes will be connected through a transistor switch so when I read the top level if it reaches any of them then the lower levels mean nothing and if the top levels are not rich then I switch to lower levels and read those but I only have npn transistors type bc547

The way the sensor is going to work there is a probe that is for sending at the very bottom of the pipe and the reading probes are above it when I do want to take a read I put the sender probe to high meaning it goes to 3.3 volts and the other problem receive that 3.3 volts the voltage needed for the node MCU to register it clearly is above 2 and maybe 2.4 volts can this be done reliably

I did try you searching for a long time and all I got is some complicated answers ai gave me some answers but it was very flaky and unreliable it the contradicted itself a lot times most of the time about the the minimum voltage required and currently cash and other stuff that I'm not really an expert about

So to recap I want to use four transistors controlled by a separate pin to turn them on and off and turning them on Bridges a gap between the lower probe and the corresponding pin

If it's doable can you explain the limitations like leaking and voltage drops as i am a beginner and thanks 🙏

Hello, as the title says is it possible to do?

More details

I'm building a primitive water level sensor to use with my nodemcu,

I don't have access to a lot of the sensors I did try to get an ultrasonic sensor which was very very bad so after some researching I found the best way is just to get a PPR pipe which is locally available and stick a bunch of graphite rods in it

But I ran into an issue where I wanted some resolution for the level sensing so I put eight levels but the node MCU doesn't support that many pins so I thought of a good idea for multiplexing since I don't have access to an I2C board to expand the pin number

The idea was that the top level probes would be connected directly to the pins and the lower level probes will be connected through a transistor switch so when I read the top level if it reaches any of them then the lower levels mean nothing and if the top levels are not rich then I switch to lower levels and read those but I only have npn transistors type bc547

The way the sensor is going to work there is a probe that is for sending at the very bottom of the pipe and the reading probes are above it when I do want to take a read I put the sender probe to high meaning it goes to 3.3 volts and the other problem receive that 3.3 volts the voltage needed for the node MCU to register it clearly is above 2 and maybe 2.4 volts can this be done reliably

I did try you searching for a long time and all I got is some complicated answers ai gave me some answers but it was very flaky and unreliable it the contradicted itself a lot times most of the time about the the minimum voltage required and currently cash and other stuff that I'm not really an expert about

So to recap I want to use four transistors controlled by a separate pin to turn them on and off and turning them on Bridges a gap between the lower probe and the corresponding pin

If it's doable can you explain the limitations like leaking and voltage drops as i am a beginner and thanks 🙏