bananasiong

Hi,
The attached diagram is the base of my robot mower. The tank circuit is used to detect the electromagnetic field produced by the 555 timer with multiple loops of wires. When the field is detected, the robot will do a "U turn". Otherwise, it just go straight.
But my problem is, when i turn on the blades, it starts going crazy. It keeps doing U turn even at the center of the loops of wires. The electromagnetic field produced by the DC motor interfere my system.
I've used the shielding method by using the alluminium foil, but i was told that, that method won't solve my problem. Yes, it doesn't, i've tried it.
So, shall i change the direction of the DC motor so that they cut off each other?
Thanks!!!

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dknguyen

Shielding works for electric fields, not magnetic fields. You know how a magnet can hold an iron block from the other side of a steel sheet? Or how a magnet will drag up a chain of nails from a bucket of nails? That's magnetic fields permeating through the metal.

Try raising the metal fence and raising the sensor on a mast or something away from the body of the robot.

justDIY

sounds like you need a form of noise rejection, although the flux generated by your motor, not to mention the spinning blades, probably over saturates your receiver... luckily magnetisim is pretty weak, so moving the sensor is the going to be the easiest first place to start

is the signal from your emitter modulated in some manner, or just a raw em field projected by a coil. if you modulate your field on the transmitter, and had a detection circuit in the receiver, that might help the system ignore the random noise from the motor and blades.

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