Customer:
I’m using Simple Rain Sensors as coolant leak detectors in an EV swap project. I connected one to a 5V supply with an LED connected to ground through AO as a warning indicator. With no liquid, the LED is off. When I add a drop of liquid across the sensor, the LED turns on. However, the LED doesn’t turn off when the liquid is removed, even if I bypass the logic board entirely.
Are these boards single use? If they’re reusable, how do I set a trigger point if it’s not a closed circuit? I noticed small concentric circles on the board that might be a reset, but I’m hesitant to experiment without knowing if the board is single use, as I don’t want to damage it.
Originally submitted via email support on 13 April 2024. Migrated to the forum for community visibility.
Soldered Support:
The boards are definitely not single use. If you’re connecting an LED to the A0 pin or any digital output pin, you need to connect a resistor in series to limit the current. I recommend 300 to 500 ohms.
I’d suggest using the D0 pin instead, which outputs either 5V or 0V with no ambiguity. You can set the threshold with the on-board potentiometer using a small screwdriver, then test it.
The concentric circles are just production markings used to align the PCB during assembly.
Customer:
With a 330 ohm resistor in-line it’s working. I’m considering wiring 2 or more sensors to a single logic board to minimize parts. Space and complexity are concerns.
The logic seems inverted from what I expected—the light stays on until it senses water. I’m planning to run a relay instead so I can activate a warning when wet.
Soldered Support:
Wiring multiple sensor boards to one logic board is an interesting idea. You could connect them in series or parallel.
If you connect two sensor boards in series, their total resistance will sum and the circuit will be less sensitive to moisture. If you connect them in parallel, the circuit will be more sensitive. The sensor wasn’t technically designed to be used this way, but experimentation should show you what works best.
Regarding the inverted logic: this breakout is meant to be connected to a microcontroller and used with the official driver library (GitHub - SolderedElectronics/Soldered-Simple-Sensor-Arduino-Library · GitHub). The driver is set to read LOW when there’s rain, which explains why it seems backwards when used directly like this.
I’m interested to hear how connecting multiple sensor boards to one logic board works out for you.