I would like to detect a persons presence with an IR light gate. Both the receiver and the transmitter side are covered by a fabric which reflects a little bit of IR. Both sides also contain parts which emit heat. The distance covered is less then 1 meter.
I have 2 options in mind:
Use an IR transistor with a simple infrared led, and detect a set threshold for the amount of received light from the IR led.
Use an IR receiver which listens for a constant pulse generated by the Arduino to the IR led.
Obviously option 1 would be far more easy then option 2, but will it be reliable, and strong enough to span 1 meter?
If I go for option 2, is the sensitivity of the IR receiver going to be a problem where it would detect the pulse from parts where the light is reflected, rather then the direct light coming from the IR led?
If I use option 2 I need to generate the pulse from the same arduino which is reading the output from the IR receiver. I found some code but apparently it requires you to set the PWM modulation at the exact speed of the IR receiver. I'm also sending data out to a DMX shield so I'm not sure if this would get me in trouble...
Can anyone think of a better approach?
I have already tried IR distance and ultrasonic, but both are unable to work behind the fabric which covers them.
You can use capacitance to vaguely sense someone's presence. The only problem is that the capacitance measured when someone is near will depend on many factors including humidity etc. It can decide if someone is there or not through.
Look up capacitance sensing with arduino and you will find some stuff.
You just have to beef up the sensing a bit
I don't think capacitance sensing would work in this case. There is a lot of electronics, incl. power supply lines and led strips nearby in multiple directions.
If you think I'm wrong please point me to a useful resource.
If you whack in a big resistor then you can sense much larger distances than the touching or few cm mentioned.
You will have to have a play around to see what kind of values you can get and as to whether it might work in your situation. I would stick up a bit of foil about 5cm sq and see how that works.
From the page:
When using this in an installation or device it's going to be important to use shielded cable if the wire between the sensor is more than a few inches long, or it runs by anything that is not supposed to be sensed.
Shielded cable to the sensor should help interference matters.
It doesn't require any extra hardware (apart from a resistor) so there can't be any harm in trying.
Thanks mowcius. I'll try it out. I'm very interested in capacitive sensors regardless if it's suitable for this situation. I like the fact that you can hide them behind surfaces
Thanks mowcius. I'll try it out. I'm very interested in capacitive sensors regardless if it's suitable for this situation. I like the fact that you can hide them behind surfaces
Yeah, I have a few projects in mind with capacitive buttons behind acrylic
