I need to take a flat surface (2'x2' sheet of plywood) and be able to place an object (turd sandwich) on the surface and read if the object is either on the surface or off of it.
Various sensing I've thought might work
IR sensing
RFID sensing
Any ideas? I'd like to keep total under $20
Thanks,
Are you looking to sense contact or sense contact from a particular object? Sensing contact would probably best be done with a resistive touch-sensor or a weight sensor (force sensitive resistor). RFID certainly won't give you contact information.
If you need to be able to identify a particular object that will be much harder.
turd sandwich? So maybe mount a mercury switch to your dog's tail and let him signal if the sandwich is on the surface or not?
Lefty
johnwasser:
Are you looking to sense contact or sense contact from a particular object? Sensing contact would probably best be done with a resistive touch-sensor or a weight sensor (force sensitive resistor). RFID certainly won't give you contact information.If you need to be able to identify a particular object that will be much harder.
I guess the first step would be to sense contact only.
I would like to place object 1 on the board. The grid/sensors would then send a message to the arduino that "an object" is on the board.
I would then place object 2, in a different location. The grid/sensor would send a message saying "another object" is on the board.
Ideally i'd like for it to sense if it is object 1 or 2. I know that would be more difficult though. I thought using an RFID reader below the board, then attaching an RFID tag to each object.
I think the limitation would be how far the reader could sense the tags.
retrolefty:
turd sandwich? So maybe mount a mercury switch to your dog's tail and let him signal if the sandwich is on the surface or not?Lefty
sometimes science needs a little visual aid
ryanmw2002:
I would like to place object 1 on the board. The grid/sensors would then send a message to the arduino that "an object" is on the board.
I would then place object 2, in a different location. The grid/sensor would send a message saying "another object" is on the board.Ideally i'd like for it to sense if it is object 1 or 2. I know that would be more difficult though. I thought using an RFID reader below the board, then attaching an RFID tag to each object.
I think your best bet for that is a force sensor to weigh the board and the things on the board. If "Thing 1" and "Thing 2" have different weights they could be detected if your weight measurement is accurate enough. I doubt you'll get a lot of accuracy for $20.
@ryanmw2002:
Placing an RFID/NFC reader below the board and placing passive RFID tags on the objects will work just fine for both proximity and identification. Certain models of reader (with their corresponding compatible tags) allow a range as much as several cm.
You might want to tweak the vertical positioning of the reader if you want to mark the detection exactly when the object actually touches the surface (as opposed to 1-2 cm above the surface).
The RFID reader cost might be a little high (> 30 USD) if you buy from a hobbyist shop or in small quantities, but you can very likely get the price < 20 USD if you buy from manufacturer.
What are you trying to design, i.e., what's the application?
Look through the following pages to get some perspective: