So I've been racking my brain for the last month trying to figure out how to make a relay turn on when a specific object gets close to it. Within 2 feetish.
I tried to use an RFID RC522 but the distance only goes a few mm and i cant figure out how to make an antenna that would stretch the signal to 24".
So now im thinking Bluetooth or WiFi.
I have a bunch of wifi esp8266's and a couple FC 14 HC06 bluetooth modules.
Can a bluetooth master detect distance of a slave reliably?
Or can the wifi modules interact to make this work.
Im going to be prototyping this on an uno and implementing it on a pro mini.
So does anyone have any suggestions.
BTW i looked at HF RFID and its just out of price range. I want to the keep the whole project around 35 to 50 dollars MAX.
So I've been racking my brain for the last month trying to figure out how to make a relay turn on when a specific object gets close to it. Within 2 feetish.
I think there are some ultrasonic modules that can operate at that range and further if needed.
I know about pir and ultrasonic distance sensor. Those work on generic input. A pir will react with anything warm and ultrasonic works with anything in front of it. It needs to be specific. Like if there where 10 tennis balls I need a way to make only one tennis ball trigger a relay from about 24 " inchs(just an example).
The battery power is a huge downside which why I originally tried nfc(rfid) but if didn't go far enough.
It needs to be specific. Like if there where 10 tennis balls I need a way to make only one tennis ball trigger a relay from about 24 " inchs(just an example).
What is going to be unique and detectable about the specific tennis ball of interest?
Thinking about it a dog controlled door would be easier to visualize what need to to.
For a clear example:
Dog A cant go outside unsupervised because it digs out of the backyard.
Dog B can go outside anytime it wants
Dog C can only go outside when owner gets home from work but doesn't need supervision so only free access from say 6pm to 1030pm.
In this situation the dog door needs to open for dog A when it gets close to the door, never for dog B, and sometimes for dog C.
Never mind the mechanics of it all.
The basic idea for that is using rfid cards in office buildings to open doors. That system works great but the range is contact thru 10mm. I need same idea but only out to 24 ". So in this example the door only opens when said dog gets within 2 feet of the door.
Ive used 433Mhz to do some projects and RFID to do others. 433 goes way to far and i cant block the signal to only reach 24".
So i was thinking bluetooth. Each bluetooth module will have its own MAC ip address so programming multiple modules to interface with a master would not be to hard to do. BUT can i make the bluetooth master know how car a slave is from it. I would think similar to a key bluetooth key finder.
Then i was thinking Wi-Fi. Wifi is pretty accurate on Db for distance but not sure if i can make two arduino wifi modules talk about distance.
Is there a third option im not even considering? Would either of these solutions be feasible? Am a pipe dreaming about something that does not exist. And if so any ideas on where to start to make it exist.
You need to research larger antennae for RFID. It is the specific technology for this purpose. What you really want is a loop around the dog door itself.
Incidentally, it always makes sense to explain your actual requirement in the first post. It's called the "XY problem".
the requirment is explained in the first post. the other posts are just clairification. I have searche dfor RFID antennae for LF and it does not get me passed a couple inchs.
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