I just got a sport bike which the frame is aluminum the engine is aluminum the swing arm as well. Basically this bike is made up of mainly aluminum and plastics with very little steel or any other metals. I have run into the age old problem of getting caught at traffic lights and not triggering the sensors in the pavement. My understanding of how those sensors work is they are nothing more than just a large metal detector and since aluminum and plastic don't do well with metal detectors, I get stuck at the lights waiting for days for it to change or hoping a car or truck pulls up to trigger the light.

My solution to this is to mount a 20kg pull electromagnet to the bike and turn it on while sitting on top of the sensors to trigger them.

So here is my question to this (multi-part) Is this just a moronic thing to even attempt and a waste of time? If it is not a waste of time, then do I have to worry about shielding the magnetic field so that it only goes downwards? I'm afraid the strength of the magnet may cause issues with the electronics on the bike, but I may just not fully understand electronics and magnets (which is why I am here).

Sorry for my long winded question I am providing a link to the electromagnet I have below.



You are assuming that the sensor in the road detects a magnet (it doesn't), or that it detects ferrous metals like iron (also, negative).

A 20 kg electromagnet might make it easier for your bike to trigger the sensor, but not because it is an electromagnet-- because you have added 20 kg of metal to your bike.

Here is a nice web page that talks about road sensor designs and how you might get your bike to be more easily sensed. Essentially, you place your bike in strategic locations on the sensor or buy a car. One note about that page: it talks about mounting permanent or electro-magnets to your bike, but that won't work well if at all. Positioning your bike is much more effective.

  • \$\begingroup\$ "[...] or buy a car [...]" +1 ;o) \$\endgroup\$ – jippie May 22 '13 at 7:27
  • \$\begingroup\$ It's not a magnet that weights 20Kg, It's a magnet that can lift a 20Kg weight (at a distance of 0 probably). \$\endgroup\$ – RedGrittyBrick May 22 '13 at 15:10
  • \$\begingroup\$ @RedGrittyBrick Thank you I was going to reply pretty much exactly that. Now that being said, seeing as how the link you provided does in fact state "These sensors do not detect the weight of a vehicle, but rather sense how much it disturbs an electromagnetic field." one would think that if you don't have enough metal on your vehicle to disturb the electromagnetic field that if you provide a strong enough magnet that it would do that work for you. after reading en.wikipedia.org/wiki/Induction_loop and en.wikipedia.org/wiki/Eddy_current \$\endgroup\$ – scripter78 May 23 '13 at 0:00
  • \$\begingroup\$ Am I crazy in this idea or is there some actual science to this thought process? \$\endgroup\$ – scripter78 May 23 '13 at 0:00
  • \$\begingroup\$ @scripter78 The problem is that it works by induction, which is a phenomenon that mainly happens with a changing magnetic field. Since the magnets that are mentioned are not changing (except to turn them on and off), it is unlikely to do anything meaningful. Car radios work by electromagnetism and they are not disturbed by static magnets either. \$\endgroup\$ – user3624 May 23 '13 at 0:11

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