If you don’t care about readings above 75psi, this should be fine. This is because electrically I think PCF8591 can tolerate 5V (if unsure, you can connect a 1K resistor inline between the sensor and A0), it’s just that (according to the graph) beyond 75psi the output will rise above 3.3V hence will saturate the analog reading. First, if you only care about readings between 0 to roughly 75psi, you can directly connect the sensor output to A0 without level shifting. There are two possible solutions for level shifting. Therefore you can only use the analog pins to interface with the pressure sensor, and not the rain sensor pin. Many the pressure sensor you referred to is an analog sensor, which is different from the flow sensors. If all of the above makes sense then would that level shifter also help the guys with flow sensor at 5V? disconnected) I read 0.46V but when I apply some pressure the reading goes up accordingly so I hope its just a matter of calculating for the voltage difference.
* The 5V from the VIN is reading about 4.798V would this affect the end result? * The above shifter is not i2c safe so does it make any difference as the A0 through A3 are only reading voltage and the PCF8591T is handling the i2c back to the Pi?
The few things I am stuck on and cannot find any answers are: I have a level shifter( ) in between OsPi and the pressure sensor. The A0 is providing 3.3V and I’m picking up 5V from VIN on the breakout at the side of OSPi. I was going to start another topic but my query is along the same lines with a 5V pressure sensor instead of flow. If your sensor outputs an digital/analog signal (and usually this means needs to be powered), it can still work as long as the output voltage is within limit (should be no more than 5V). The sensing pin is pulled high normally, so when the sensor switch is open, the sensing pin reads a digital high, and when the sensor switch is closed, the sensing pin reads a digital low.
All rain sensors and dry contact flow sensors are such type of sensors - they are essentially rain-activated (or flow-activated) switches. Technically, the sensor terminal on OpenSprinkler is designed to connect to a ‘switch-type’ sensor. It’s still possible to get it to work with OpenSprinkler, but you will need to find out how the flow sensor works first. If the flow sensor comes with 3 wires, you will have to check the datasheet / spec to find out whether it needs to be powered, and what type of contact it provides. You can just wire it to the rain sensor terminal, and go to Edit Options -> Weather and Sensors to select the sensor type as ‘Flow’. If your flow sensor comes with 2 wires, most likely it’s supported.
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