Sonar Light Switch

I use this sketch for an outdoor light in the middle of a stairway. There's also a light on a porch at the top of a second, higher run of stairs. Both lights are connected to TP-Link Kasa smart switches (HS-200). The stairway switch is programmed to turn off power to the stairway light during the daytime. That also turns off power to the Arduino, so motion during the daytime will not trigger the light.

When the Kasa switch for the stairway light is on, the light still will not turn on unless a pin on the Arduino is held high, triggering a relay. That is, the stairway light is controlled by two switches in series, both of which must be on for the light to be on.

The sketch is designed for use with an Arduino Uno WiFi rev 2, so we have a network interface. We also use two ultrasonic ranging sensors (HC-SR04 clones) that detect bodies below and above the stairway light. A body at either sensor will trigger the stairway light. The light stays on until no body is detected at either sensor for a set period of time.

If we determine that someone is walking up the stairs (i.e. the light was turned on because someone walked through the lower sensor, and they then walked through the upper sensor), we also send a message to the porch light switch to turn the porch light on. We do not ever turn the porch light off, because the light might have been turned on manually, and we don't want to turn it off in that case.

Note that if someone comes and drops off a package (walking through the lower and then the upper sensor), this could leave the porch light on until morning (when the smart switch is programmed to turn off the light). But this could also help us notice that something has been dropped off.

(We actually also have a third light, between the stairway light and the porch light. That light is controlled via its own integrated PIR sensor, which operates entirely independently of the porch and stairway lights.)

DYP-A02YYWM is a sealed waterproof ultrasonic ranging sensor that is compatible with HC-SR04. It uses this wiring scheme:

red +5V

black ground

yellow trigger

white echo

Cat5e CMR used for connections:

blue trigL

blue-w echoL

orng trigU

orng-w echoU

grn light

grn-w +5v (if vin is not +5v)

brwn gnd

brwn-w vin

Debug messages are sent to console, and less verbose log messages are sent to a Google Form. To set up the form, create a Google Form with a single short answer field. Type anything into the short answer field, click "Get pre-filled link," click "Get Link," and then click "Copy Link." From the copied link, the long string after "/d/e/" is the formID, and the number after "entry." is the entryID, which should be defined in the global constants in the sketch.