In function of an art project I want to make a led board (6x48) with red leds. Each 6x6 ledmatrix shows one letter. A sensor (thermal sensor?) connected to the arduino decides if the board shows “ENTRY” or “NO ENTRY”. If the board reckognizes a human presence the ledmatrix must show “ENTRY”, If the board doesn’t reckognize a human presence it must show “NO ENTRY”.
My plan: instead of working with a led matrix, I would just connect the LED’s that need to light up.
my questions:
is there an affordable sensor that can get the job done?
what would the code for this project look like? (i know electronics, but don’t have much arduino experience)
You could just use a light beam. When the beam is not broken display one message, when it is broken display another.
You could use an ultrasonic sensor to detect something approaching the installation. A lot depends on the geometry of the situation e.g. how people will approach and leave the exhibit. You also need to think about how you handle multiple people.
An HC-SR04 ultrasonic range finder is cheap and generally good for detecting presence. It can't tell a human from any other object but what other objects do you expect to be moving around in your display space?
I clarify, I want people to stand for the sensor and the sensor needs to read if the person for the sensor is a human or for example a can of coca cola.
So a lightbeam won't do the trick. It needs to measure the difference in temperature and preferrably after the subject takes place after the sensor and waits 10 seconds, or pushes a button,...
You might be able to tell a human from a coke can but telling a human from a cat or dog might not be that easy. There may also be issues with what people are wearing, the ambient temperature and any heat sources in the area.
A PIR sensor detects movement of warm objects, such as a person. Stationery warm objects are ignored.
The can of coke is also easily distinguishable from a human using a break beam sensor, by simply placing it above the height of that coke can.
An ultrasound sensor placed above can also simply be set to ignore all objects under it that are less than 90 cm above the floor. Some really short people and very small children may not be detected that way, but the vast majority of people will. The can of coke will also not set it off - but the human placing that can there, may, but that's OK as it's a human which is what you want to detect.