Magnetic intensity transmitter + magnetic intensity sensor.

Hi friends , I am new to the forum , I have a good hardware+ software background, and I have done many project using microntrollers.

I have some questions and I wish you here guide me to the best solutiob before I start .

Problem : I have to design a magnatic intensity tranmiter( magnit) and a detector circuit. The aim of this is to be used in a robot , the robot will be inside a pipe and from out side the pipe we would be able to give the robot position to stop .

I have some ideas how to start but I dont know if I am in the right direction .
For the transmiter , I am going to design a seliniod with DC volt , but I have lack of information how to design the selinoid, or if there is better solution . and should I feed the seliniod with DC voltage ?

for the detect circuit , I am going to select one of the linear guess sensors.

note that the distance between the transmitter and reciever can be up to 1 meter .

please any suggestions would be helpful .

Thank you

A solenoid is a good idea.

Idea 1.
Use a magnet and a 2 or 3 axis detector.
North points down the pipe = go.
North points back up the pipe = reverse.
North points up = ?
North points down = ??
No magnet = stop

Idea 2.
Run AC through the solenoid. Build a receiver that only detects that frequency. Stay away from 50/60 hz. You can modulate the amplitude or frequency to send commands to the robot.

A few questions about your project, what is the pipe made from ? What positional accuracy are you needing ? What distance down the pipe will your robot be ?

Thank you for reply ,

The pipe made up from IRON , and it size mat change , the robot abd magnetic reciever will be inside the pipe and the transmitter will be out. the max. distance between them is 1 m .

Thank you again .