Since the detector coil picks up the magnetic field from the motors then your project doesn't work. Can you mount the detector coil out on a stick in front of the robot?

Yes.

Connect a 0.1uF ceramic disc capacitor at the supply pins of the LM393.

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Uncle $crooge

 

The tank circuit is already sticked in front of it, but still affected, i'm worried that, the wire connected from the tank to the input of the 393 will pick up the field.

one end to the +ve and the other end to the -ve? means that in parallel?

*Can i shield the wires or shield the motors with the alluminium foil to avoid the interference as i mentioned before?

 

Connect the metal covers on the motors to 0V with a wire.
Use shielded cable like is used to connect stereo components together (cut off the RCA connectors) to connect to the tank.

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Uncle $crooge

 

Yes.. Thanks.. The metal body of the motor won't cause any short circuit if connected to GND, will it?
Then do i still need to include the bypass capacitor?

What is shielded cable? How to get it? Can i make it myself? What is the RCA connector?

*I need to use a diode to make to current to flow only one way, it is connected series with 2 DC motors. I was using 1N34A, but after it was turned on and off for once, the diode burned (i think) and cause open circuit. So i replace it with a 1N4001, now it works well.
My question is, if i replace the 4001 woth a LED, does it use more current?

 

Probably not.

Of course it is needed.

In my country, the stereo tuner, CD player and amplifier are connected together with shielded cables with RCA plugs. I cut off the plugs and use the shielded wire.

I don't know why current in your circuit doesn't flow one way without a diode. Is it AC?
Look at how much current the motors use when they work hard. Much more current than the max current ratings for the 1N34A or an LED.
Don't use an LED in series, connect a current-limiting resistor in series with the LED and connect the combination to the power source of the motors to indicate when they run.

__________________
Uncle $crooge

 

I've shielded the wires and the motor. I've tested using batteries which are fully charge and not fully charged (not full). When i use the lower power, my robot mower operates well, no interference. When i use the fully charged batteries, of course, the motor run faster and interference occurs.
The motor should run as fast as possible for good mowing system, but the electromagnetic field produced by the motor is bigger.
Can i shield the wires and the motor thicker (turn more round) to solve this? I use alluminium foil (for cooking) to shield them.

 

Shielded cable or aluminum foil will stop the sparking of the motors from radiating electrical interference. But will do nothing for the magnetic interference.

__________________
Uncle $crooge

 

!!?!???!?!?!??
What should i do besides moving them far away to each other?
Is there anything to remove or direct the unwanted electromagnetic field to somewhere else?

 

I guess using a coil for a sensor is not the correct thing to do in a machine that is powered by electric motors.
Hee, hee. Diesel engines? Hee, hee.

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Uncle $crooge

 

Oh no... you're kidding right? I mean the diesel engines.. haha.. i use only AA's.. I'll try to solve it..
Anyway, you've helped me a lot, thank you very much.

 

Hi, I've found this, but don't know whether it helps or not. I'm still reading it. Sharing is caring.. hehe..

Attached Files

Shielding Interference.pdf (688.9 KB, 14 views)