Heltec-Aaron-Lee OLED ESP8266 Keystone Project Box

thingiverse

I have an ESP32 board with OLED display from Heltec-Aaron-Lee called the WifiKit_8. People say that the ESP32 is 5v tolerant even though it's a 3v3 part, but I'd rather not take that risk. So I built a little voltage conversion circuit using a PN2N2222 transistor and three resistors (one just to pull up my sensor device output to 5v). To house this safely, I decided to build a protective box around the GPIO HV<->LV circuitry. The box had to accommodate the USB input for power, programming, and datalogger functionality, as well as a Keystone jack on the other end to connect my sensor. My sensor is a Digiten G1 water flow sensor with 5v hall effect sensor. I heated the little bridge lock piece with a lighter once I got 99% locked to make it pliable and easier to snap all the way to 100%. Maybe I'll redesign that area if I end up making more projects with these Heltec parts. Perhaps shaving 1mm off the bottom of the bridge would be a good idea. I wrote some Arduino code that measures the flow rate and moves a little ball across the screen in proportion to the flow rate. The indicator ball turns into multiple balls and moves faster as the water flow rate increases. This flow rate is sent via Wifi and MQTT to my OpenHAB2 controller, where it's logged into InfluxDB and graphed via Grafana. I just strap this little module onto the CPVC pipe next to the Digiten G1 sensor, plug in the RJ14 jack, and apply power via a USB cable. I can visually see when water is flowing and see the flow rate. Part of why I'm using this is to detect slow leaks in my house and also foundation/slab leaks.