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Do you have a question on Embedded electronics and controls? Ask our Expert, Paul Clarke

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Paul Clarke

Paul has 20+ years of working as a digital electronics engineer and has strong software skills in assembly and C for embedded systems. Currently developing embedded electronics for thermal management control solutions for the air movement industry (HVAC & RAC).




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  • Hello Paul,

    i have a rather strange question that im sure has a simple answer, i hope i am asking the right person!!

    I am currently trying to make a 'magnet detector' and install it into a mans wrist watch, i really have no idea on which direction to take to create this circuit, all i have at the moment is some 10mm coin vibration motors (to secretly inform me once i am near the magnet) a small reed switch, and some 3v cell batteries. as the circuit is going to be built into a watch, it has to be fairly small and compact, but i do not know whether i need more than just the battery/reed switch/vibration motor hook up to achieve this or whether there has to bo some kind of amplifier or constrictor to ensure the circuit doesnt short out or anything. i am hoping that you might have some advice on how to make this and whether it might be better to purchase some hall effect sensors rather than the reed switch.

    thanks for any help you can offer me

    kind regards,

    Ben.

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  • Hello Paul,

    i have a rather strange question that im sure has a simple answer, i hope i am asking the right person!!

    I am currently trying to make a 'magnet detector' and install it into a mans wrist watch, i really have no idea on which direction to take to create this circuit, all i have at the moment is some 10mm coin vibration motors (to secretly inform me once i am near the magnet) a small reed switch, and some 3v cell batteries. as the circuit is going to be built into a watch, it has to be fairly small and compact, but i do not know whether i need more than just the battery/reed switch/vibration motor hook up to achieve this or whether there has to bo some kind of amplifier or constrictor to ensure the circuit doesnt short out or anything. i am hoping that you might have some advice on how to make this and whether it might be better to purchase some hall effect sensors rather than the reed switch.

    thanks for any help you can offer me

    kind regards,

    Ben.

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  • in reply to e14 Contributor

    Hi Ben,

     

    I assume you are trying to measure a DC magnetic field from a standard magnet?

     

    As you have said your circuit will be fine to use, however reed switches need a medium sized magnetic field to respond to. I'm guessing you want to measure very weak fields? You’re going to need something more specialized I think. Not done anything like this myself but think may you want something like a digital device to detect changes in field that’s designed for the job.

     

    However, if you had a ferrite rod and a winding around it and then feed it with a fixed frequency it would have a fixed impedance. As the magnetic field around it changes, so would the flux density in the air and so the inductance.... I think?

     

    To be honest its really not my field (LOL) of expertise but that’s how I would start off.