I will have multiple cabinets next to each other in a room. Each cabinet will have a sensor located at the top. Within the cabinet will be multiple other sensors at different heights located on shelves. I want the sensor at the top of the rack to be able to locate all sensors within its own cabinet and also determine the height of each sensor.
Im not concerned about its exact position in the cabinet, only its height. I figured it would be easier to accomplish this by placing a sensor at each cabinet instead of using triangulation with a few sensors within the whole room. This could also help make the margin or error smaller, hopefully down to half an inch.
What do you think would be the best way to measure the distance to determine the placement of the sensors height (Y axis)? Also willing to play around with different methods: infrared, RF, etc.
I guess it would make more sense if I explained the complete use case.
I have a plant store. Within the store I have 30 cabinets. The cabinets hold trays of plants. The plant trays differ in size and they slide in and out of the cabinets. There are 50 slots within the cabinet. A tray can slide within each cabinet at any of those slots. I want to place a sensor on one of the trays and when i move it in and out of the cabinet it will update my database and let me know where it is. The trays will be constantly moving from cabinet to cabinet depending on where the plant is in its growth cycle.
Once I am able to determine the distance the tray is from the reader on the cabinet I can associate the distance to match the number labeling system on the cabinet so i will know exactly what slot the tray is in.
There are no sensors that do what you want. Estimating distance between two “sensors” is a notoriously difficult problem.
In general radio does not work to determine distance between a transmitter and receiver, except under special circumstances that would be difficult to realize in your application. Nor can I imagine how IR could be made to work.
Video cameras or laser scanners can be used to identify and locate visible tags, or short range RFID tags and readers could be used at to determine presence or absence of a tagged object in a particular location.
I’ve recently seen ads for a commercial radio module that can be used to accurately locate a single object within a room, but it works similarly to GPS and relies on the presence of several specially coded transmitters placed at nearby known locations. The system is not cheap.
I think the RFID solution of a tag moving over a fixed antenna (or a linear array of multiple near-field ones if trays can be next to each other) as the tray is sliding in and out of the cabinet is the simplest (and maybe cheapest) to locate presence and general location. As the trays are pulled out of the cabinet each tray-tag will pass over the antenna and will identify itself in the sequence it is placed. Then as the trays are pushed back in the cabinet the changed sequence can be compared to the previous, and updated into the database. You may need a sensor to measure how far the cabinet is extended as it is pulled out and in. But that is one dimensional linear, and much simpler to do than 3D trangulation in space based on other sensors. Try to fix as many variables in the problem as you can. Sensors measuring other sensors positions measuring other object is asking for positional inaccuracy growth.
: