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Topic starter
2020-06-26 8:15 am
Hi guys ,
My name is jaap , i am.new i have introduced myself.
Correct me if im wrong but i need some help
I am using a pir sensor HC-SR501 contected to my Arduino uno.
When it detects movememt it prints to the serial port something like hey i see you and it flashes some led.
Now theres two dials on the sensor that 1 is for sensitivity and the other for time.
Now i am running into a bit of a problem where definantly need someone to help me out.
The sensor should only go of when it detects a heat object.
But now when i throw a towel in front of the PiR it will go off, even if i screw the senstivity dial it does not help
It works as a movement sensor but not as an PIR sensor thats the issue.
I need someone that can help write a basic example that only goes of when it detects a larger heat source and not with small objects that dont have Heat.
My idea is to create a proxyimity alarm for camping.
So when i sleep at night and someone is approaching me to my tent i want the alarm to go off wireless into my tent.
But when some little squirrles passes by or a bird flies in front of the sensor i dotn want it to trip the sensor or some brenches that fall from the trees.
If i could only get someone to help me out with the large heat source detection then i think i can manage the rest with the wireless alarm.
Or maybe i am using the wrong sensor, if u have suggestions please be welcome to assist.
I hope i get someone excited to help me out.
This topic was modified 4 years ago by jaapspijkerman
2020-06-26 1:08 pm
A PIR sensor doesn't detect heat, it detects movement. That is why you are getting alerts even for a towel.
The adjustments are so you can adjust for how much movement it takes to trigger an alarm. That way you can adjust so that it won't trigger on small animals, but only larger objects.
SteveG
Topic starter
2020-06-26 1:12 pm
PIR-based Motion Detection:
In this case motion is detected by means of a PIR sensor, a passive infrared sensor. This sensor detects emitted infrared energy from objects (humans and animals, but also cars) in the form of heat.
In general differences of around 5-10º Celsius compared with the ambient temperature in the field of view and within a 10m /30ft range of the camera are detected.
2020-06-26 1:19 pm
Not how I understood how they work, but I'll wait for others to chime in.
SteveG
2020-06-26 1:26 pm
PIR sensors detect "motion" not just the temperature of an object.
SteveG
Topic starter
2020-06-26 2:55 pm
I have an alarm already it has exact same pir sensor and it detects only humans and large animals and it doesntmt detect just motion.
Only its not an an arduino object but anyway lets not start some yes or no discussion its not of any benefit to my project, i need help and my project is standing still right now.
Thanks for a reply.
2020-06-26 3:14 pm
I'll let others try to help you and I'll stay out of the fray.
SteveG
2020-06-26 7:18 pm
This sensor uses a pair of pyroelectric elements that react to changes in temperature. Instantaneous differences in the output of the two elements are detected as movement.
A fresnel lens is placed in front of the passive infrared sensor to direct radiation from a wide area. So my guess is unless the human is generating more heat than a small animal there is no way it can distinguish between the two heat sources. The heat generated by a human would also depend on the type and amount of clothes being worn.
Perhaps the fresnel lens can be partly covered to only allow heat radiation from a tall object (human) reaching the sensor?
https://ajax.systems/blog/what-is-pet-immunity-in-motion-detectors-and-how-to-use-it-correctly/
A complete solution would of course be an expensive infrared video camera and some sophisticated image processing 🙂
2020-06-26 11:51 pm
A human will emit effectively the same temperature wavelength as a squirrel or a bird, but the human is a bigger heat source, so is more likely to trigger the device. If you don't want small hot moving objects to trigger the detector you may have to have the lens shielded in some way, or angled, so that they do not enter the field of view. Or consider requiring the heat to be detected for a certain period, longer than the traverse of a squirrel or bird through the field of view. I don't know if the average PIR detector module can do that.