Alright, so I wanted to mess around with smart building stuff, specifically figuring out how many people are in a room. It’s all about that occupancy management, you know? Here’s how I tackled it.
First things first: The Goal
Basically, I wanted to build a system that could count people entering and exiting a space, giving me a real-time headcount. This could be useful for anything from optimizing meeting room usage to making sure we’re not overcrowding the break room during lunch.
Picking the Tools
I decided to use a Raspberry Pi as the brain of the operation. It’s cheap, small, and I already had one lying around. For the actual people counting, I went with a couple of infrared (IR) break beam sensors. They’re simple: a beam of light gets broken when someone walks through, and that triggers a signal.
The Setup: Simple but Effective
- The Sensors: I mounted the IR sensors on either side of a doorway. Important thing is to make sure they’re aligned properly, so the beam goes straight across.
- The Pi: I wired the sensors to the Raspberry Pi’s GPIO pins. Each sensor got its own pin.
- The Code: This is where the fun began. I wrote a Python script to monitor the GPIO pins. When a sensor’s beam is broken (signal changes), the script registers it.
The Code Logic: Figuring Out Direction
The trick is figuring out which direction people are walking. This is done by comparing which sensor is triggered first.
If Sensor A triggers before Sensor B, it means someone is entering the room.
If Sensor B triggers before Sensor A, someone is exiting.
The code looks something like this (super simplified):
import * as GPIO
import time
sensor_A = 17 # GPIO pin for Sensor A
sensor_B = 27 # GPIO pin for Sensor B
*(sensor_A, *, pull_up_down=*_UP)
*(sensor_B, *, pull_up_down=*_UP)
count = 0
def sensor_callback(channel):
global count
*(0.1) # Debounce (very important!)
if *(sensor_A) == *:
if *(sensor_B) == *:
count += 1
print("Entering:", count)
else:
print("False trigger on A") #Ignore for now
elif *(sensor_B) == *:
if *(sensor_A) == *:
count -= 1
print("Exiting:", count)
else:
print("False trigger on B") #Ignore for now
*_event_detect(sensor_A, *, callback=sensor_callback, bouncetime=200)
*_event_detect(sensor_B, *, callback=sensor_callback, bouncetime=200)
try:
while True:
*(0.1)
except KeyboardInterrupt:
print("Exiting...")
Debouncing: The Key to Accuracy
Okay, so IR sensors can be a bit jumpy. A single person walking through might trigger the sensor multiple times in quick succession. This is called “bouncing,” and it will mess up your count. To solve this, I used a “debouncing” technique. Basically, the code ignores any sensor triggers that happen within a short time period (like 100 milliseconds) after the initial trigger.
The Result: It Works (Mostly!)
After some tweaking, I got the system working pretty well. It’s not perfect. If people walk through too close together, or if someone lingers in the doorway, it can get confused. But for general occupancy tracking, it’s surprisingly accurate.
Next Steps: Making it Smarter
I’m thinking about adding a few upgrades:
- A Web Interface: So I can see the occupancy count on a dashboard, instead of just in the terminal.
- A Better Sensor: Maybe upgrade to a more sophisticated sensor like a Time-of-Flight (ToF) sensor for better accuracy.
- Data Logging: Store the occupancy data over time, so I can analyze usage patterns.
Final Thoughts
This was a fun little project. It shows that you don’t need fancy equipment to get started with smart building technology. A Raspberry Pi and a couple of cheap sensors can go a long way! Give it a shot – you might be surprised at what you can build.