I wish to make a wireless transmitter project with a range of about <=20cm
I only need to transmit 1 bit (1 or 0)
I have seen several projects on the net but they are too big and complex for my needs.
The transmitter needs to be very small (3 or 4 small components max)
It will have an input voltage of 6v when i want it to output 1 and 0v when it outputs 0
The reciever can be bigger and will be powered by 2 9v batteries. The reciever must be able to operate a relay when it recieves 1.
There will probably not be a direct line of sight between the two devices.
As an addition i want to allow several of these devices to operate near each other (within 2m) without them interfearing with each other.
Im not sure whether to use IR or RF or even ultrasound!
I really need to minimise the size of the transmitter.
I have done electronics for a few years but i thought id ask the experts before i buy the components.
Any help or suggestions are appreciated.
If anyone knows any good websites with relevant information or simialar projects i will be gratefull too.