Magnet Sensor

Other Hardware Sensors
1

Hello guys,

I am trying to make a robot that follows a certain user defined route. It has to be capable of doing so in the Canadian winter (i.e. snow). My initial idea was to use a colored tape and follow that using a color sensor. However, the tape will get covered by the snow and this method will not work. Therefore I need another solution. I have two rough ideas and if anybody could nudge me in the right direction I would be very glad.

  1. Can I use the same tape and color sensor concept however with something else? Maybe some sort of tape that could be sensed by a sensor without actually being in sight of one another. I am not even sure if it is possible but if something clicks please let me know.

  2. Place magnets on the ground before the snow falls and use these as checkpoints. I could probably place a strip of magnet on every turn. I would need an Arduino compatible magnetic sensor. Can the magnetic sensor pick up the signal through a few centimeters of snow? Anybody has experience with these? Which one do you recommend (I was able to find that A1302 to be used by someone who had posted previously but would it work for my application)?

2

Getting a magnetic sensor to work reliably through a few cm of snow might be difficult. How accurate must the robot route be? Maybe a GPS unit would be an option.

3

"Strip magnets", the rubbery kind, should be tested so you're certain they're magnetized as you're expecting. These are typically magnetized with an alternating N and S through their thickness. The magnetic field is very short and you probably can't pick it up with a hall sensor at any appreciable distance.

Hall sensors work with snow just fine -- magnets still work underwater so why would snow be any different? The only question is how large a magnet you will need to get the necessary distance between the hall sensor and the magnet. The A1302 outputs 1.3 mv/G, and with ceramic magnets around 3000G on their face you should be able to get that couple-centimeter-distance.

Note that the A1301 is about twice as sensitive (2.5 mv/G) as the A1302.

4

Thank you for your response. I am going to design my project and see how much distance I can get with both the sensors. I will update you when I am done :slight_smile:

5

Chagrin:
Hall sensors work with snow just fine -- magnets still work underwater so why would snow be any different?

Poorly worded in my reply.

Getting a magnetic sensor to work reliably through a few cm of snow might be difficult.

was not meant as a reference to snow being the problem but the distance.