My HC-SR04 sensor box

My HC-SR04 sensor box

I designed this box that will house a HC-SR04 ultrasonic sensor, an arduino nano, a MP1584EN adjustable 3A bucking power supply, a Songle SRD-05VDC-SL-C relay, a 5mm LED, and 2, 2 pole pcb screw terminals. The sketch and schematic are included. I used the arduino relay circuit from here:
https://www.instructables.com/id/Arduino-Relay-Circuit/

My goal was to create an ultrasonic eye that I can install into a packaging machine that has 24vdc for a supply and will need a NO dry contact for a signal. I tried to make it look industrial, even though I am using hobby grade components. Industrial grade ultrasonic sensors costs upwards of $500.00 and I think I can mimic their operation for about $10.00. The HC-SR04 looks suspiciously similar in the $500.00 units.

There is a box, a lid, and a door. It measures 60mm X 60mm X 30mm, when assembled, with a through hole in the middle for an 8-32 screw. The screw will hold the lid on and provide a mounting point. I ha