I am new to radio communication and I'm working on a project that may benefit from the use of it.
For my school project, I'm making essentially making a bike speedometer (monitors cadence not speed however) that has 3 outputs (LEDs) that need to turn on dependent on the speed (RPM pedals).
At the moment it is wired however I was wondering how I would go about making an AM transmission and receiver circuit that could send the logic levels of 3 inputs essentially.

I was wondering if I could use an op-amp set up in a summing configuration to encode signal, the output of this would control the amplitude of the wave being transmitted by a crystal. (I have absolutely no idea whether this is common practice or even possible)
I don't mind if the final design is crude and very simple, it just needs to transmit the states of 3 inputs over a distance of a metre or 2 (I could even adapt my circuit to output an analogue voltage ranging between 0v and 3v if necessary).

Help appreciated.
PS. I attached my original circuit which I can explain if necessary

 

The simplest solution is to take apart a radio controlled toy or a wireless door bell.
Control the duration of the transmitted RF signal, three different times for three LEDs.
This is called pulse-width modulation or PWM.

 

I'm afraid that it will be more complex than that. You could possibly send different tones for each signal and filter them on the receiving side.

You could also send short bursts which could be a specific length for each signal -- or perhaps each signal would generate a pair of bursts with a fixed time between them.

Amplitude alone would probably not be very reliable because the reciever wouldn't have anything to reference it to. That is, it would be hard to determine if the received signal represented a high, medium, or low ampliutude.

There are commercial products that could work.

Good LUck,

hj

 

Thank you for the advice