I'm setting up a project to monitor a room in several points and variables (temp, humidity, CO2 etc). I'm using DHT22's and for the CO2 i'm still looking for a sensor (open to advice for this too!). The arduino will also control several relays accross the room.
Here's the thing, sensors will be spread throughout the room and far away from the arduino (max distance about 10m), should I just wire the whole room? Meaning one long wire per sensor? I feel there's gotta be a better way to do this, i just don't know what it is.
Also, how long can a wire be before arduino stops reading the sensor?
The BIG problem with wiring is interference from AC devices. You need to exercise careful design if you use copper. You could, obviously, use fiber-optic but you will need to buy/create the interfaces.
Search the Web for articles and principles to reduce hum.
Twisted, low-capacitance, shielded cable and keep the runs as short as possible. ONLY the master Arduino should be the ground point for all the shields... the other end should be left unconnected. If you can afford it, Cat5 digital cable would generally be acceptable for such use although you may be able to get away with short runs of premise telephone wiring. Cat6 digital is better but it is a physically larger cable and more costly. IF YOU are going to remote thermistors or thermocouples, there is an entire science behind this which is not for the faint-of-heart.
Twisted, low-capacitance, shielded cable and keep the runs as short as possible. ONLY the master Arduino should be the ground point for all the shields... the other end should be left unconnected.
What do you mean the other end should be left unconnected? Wouldn't you need to run 3 wires from every sensor? Input, power, and ground all to the Arduino?
What do you mean the other end should be left unconnected? Wouldn't you need to run 3 wires from every sensor? Input, power, and ground all to the Arduino?
The Shield is grounded at only one end.... the Arduino (hub).... think STAR topology. The sensor end of the shield is left open. http://www.rane.com/note151.html
Not to be (overly) critical, but when starting a project it is good to also learn a little theory as you progress in your Arduino knowledge. Being well-rounded will make you far more competent in this life than knowing everything there is to know about one technical subject. Google is your friend. We live in a world where the Internet is simply the world's largest library... YouTube has great tutorials as does numerous other sites. I watched one yesterday by Jeremy Blum... he does a good job.
Continue to ask, but try to make sense before responding too quickly. I spend most of my limited time handling the "0" response on the forum that no one else will handle because the subjects are either too elementary or too vague. You can help me by digging in just a bit, too. We're a team here.