Movement Sensor

Hi Guys,

I need your help for a simple but complex project for a newbie like me.

I need to create 4 tiny sensors (as small as possible, including battery), that once they are moved the would send a wireless signal to a box that would turn on a LED.

So exemple, if I put the sensor on a door and the door move, it would turn on a green led on a wireless box.

I guess I need some type of tiny wireless accelerometer. I don't need to know what direction it moves, nor velocity, nor speed, nothing. Just the fact it moved is fine.

Another idea I had was to put a magnet on the door, and use a magnetic sensor to see if it's close or not. But it would need to be about 4 inches away so I don't know if that would work. But it would remove the whole wireless part.

Any ideas?

.. the door thing is just an exemple.

What are the orientation requirements? Will the sensor always be upright? What kind of movements? All drastic door swings or down to vibration sensing?
Affixed sensors or self contained?

I guess I need some type of tiny wireless accelerometer.

And as they don't exist then you will have to get a sensor and attach it to a wireless transmitter of some sort. Perhaps an EPS8266 can read the sensor and act as a web server to push the reading to a web site.

The problem is that the accelerometer needs to be constantly read to know when it has moved and that takes power. I am guessing you want to power it off a tiny battery that runs for yonks.

a simple but complex project for a newbie like me.

No it is a reasonably complex project for anyone, given your full intent of power supply requirements. Or do you not mind changing the batter every day or so?

I think a dumb rf transmitter triggered with a mechanical sensor (ball switch, tilt sensor, two part magnetic trip, whatever) is how those As-Seen-On-TV ones work. Not that demanding of power.
I presume the receiver unit will be plugged in so not worrying about that. Then it would send led on/off signals to that box.

Thanks for replies

To answers the questions:

  • I don't care about the orientation, if it moves, I want to know.
  • The transmitter would only work for about 60 minutes, after that I will turn it off.
  • I don't need anything fancy (like a webserver). The transmitter moves, it trigers a led on the receiver.
  • The receiver unit will be plugged, no worries about the power.

Sorry about the door exemple, probably not the best one to give. Here what I want to do: There is 4 objects on a table with the tiny transmitter inside them. When someone pick-up an object, the receiver LED will turn on according to the transmitter that was picked. So transmitter 1 = red led, transmitter 2 = blue led, etc.

Still didn't clarify orientation. I mean is the sensor going to be mounted to something that doesn't rotate? Reason I ask is to see if a tilt sensor would be sufficient. Like you might've seen in some arcade skill games- dangling weighted wire passing vertically through a horizontal plane ring. Movement makes dangling wire contact ring, complete circuit, and trip alarm.

INTP:
Still didn't clarify orientation. I mean is the sensor going to be mounted to something that doesn't rotate? Reason I ask is to see if a tilt sensor would be sufficient. Like you might've seen in some arcade skill games- dangling weighted wire passing vertically through a horizontal plane ring. Movement makes dangling wire contact ring, complete circuit, and trip alarm.

The sensor would be put inside an object at any angle (would not necessarly be horizontal). There is a good chance that the sensor will be rotated when it's picked up from the table but it might remain at the same position, just moved.

However, to make sure it's 100% accurate, maybe something that would detect any movement?

As long as it can be "set" in a known orientation, then the job is simpler to detect movement. It just might not be automatically resetting unless put back down juuust right.
If rotation is guaranteed, tiny ball switch will do the trick.

INTP:
As long as it can be "set" in a known orientation, then the job is simpler to detect movement. It just might not be automatically resetting unless put back down juuust right.
If rotation is guaranteed, tiny ball switch will do the trick.

Awesome! Any recommendations on a tiny wireless transmitter?

I guess that the transmitter would need to send an ID or something to identify the right transmitter?

I only have experience with IR, RF, and bluetooth. I'd rule out bluetooth. IR works if you have line of sight.

Finding RF modules with 2262 and 2272 chips can let you use 4 channels so each sensor transmits a different code and readable by one receiver. The "tiny" requirement might have to accommodate an antenna depending on how far you expect the sensors and receiver to be apart from each other.

Oh, that's such a great idea!

I could probably buy something like this: http://www.electrodragon.com/product/2262-2272-wireless-module/#prettyPhoto with 4 remote, and then i would remove the buttons from the transmitters, and replace with tilt sensors. So a tilt sensor at the place of button 1 for transmitter 1, sensor at the place of button 2 for transmitter 2, etc...

Make Sense?

That'd be a good idea to explore, yep.