​ ​ ​ ​ Magnetic sensor required - Page 7
Page 7 of 8 FirstFirst ... 5 6 7 8 LastLast
Results 61 to 70 of 71

Thread: Magnetic sensor required

  1. #61
    Senior Member
    Join Date
    Aug 2008
    Location
    West Midlands, UK
    Posts
    1,104

    Default

    In the UK our upbringing may have been sufficiently sheltered for us not to know! Not sufficiently sheltered to avoid the effects of the rain though.

    I used to think it sufficient to know that Blue had red hair . . .

  2. #62
    Member
    Join Date
    Jan 1970
    Location
    South west, West Australia
    Posts
    76

    Cool

    Quote Originally Posted by marzan View Post
    Anyone in Oz would know you were an aussie with a nickname like freddagg
    I think the original was a kiwi. He now calls Australia home.

    Q. What is the New Zealand national anthem?
    A. I still call Australia home.

    Fred

  3. #63
    New Member
    Join Date
    Feb 2014
    Location
    New Zealand
    Posts
    18

    Default

    Yes Fred, your name-sake is a Kiwi character, real name John Clarke.
    from his version of the Newcastle Song (covered from an Aussie character) ' dont you ever let a chance go by...'

    To return to topic, thanks for all the code in this thread, i am about to have a go at making an HMC5883L work.

  4. #64
    Senior Member
    Join Date
    Oct 2012
    Location
    Florida, United States
    Posts
    228

    Default

    The HMC5883L mentioned in the above post by MFB would be the way I would go. It is very small and can be remotely located a few feet from a picaxe so it is easily buried with a very small footprint. It looks so cool I am temped to try one just for fun, well, not know, need to finish up my PicAxe powered wooden clock.

  5. #65
    New Member
    Join Date
    Nov 2017
    Location
    United Kingdom
    Posts
    5

    Default

    Quote Originally Posted by binary1248 View Post
    The HMC5883L mentioned in the above post by MFB would be the way I would go. It is very small and can be remotely located a few feet from a picaxe so it is easily buried with a very small footprint. It looks so cool I am tempted to try one just for fun, well, not know, need to finish up my PicAxe powered wooden clock.
    I realise that this is an extremely old thread and I apologise for resurrecting it, however, I have a question. It is not clear which PicAxe chip was used with the HMC5883L. Was it the 08M2?

    Regards

  6. #66
    Member
    Join Date
    Jul 2014
    Location
    South Carolina USA
    Posts
    96

    Default

    Cheapest, simplest, most reliable method:
    Two sealed rubber hoses tied to pressure switch. Photo taken when front wheels hit 2nd hose.
    You will receive your speeding ticket in the mail. Y'all come on back down to south Georgia now you he'nyuh.

  7. #67
    Senior Member
    Join Date
    Feb 2012
    Location
    London
    Posts
    2,717

    Default

    Hi,

    Quote Originally Posted by Nelixuk2003 View Post
    I realise that this is an extremely old thread and I apologise for resurrecting it, however, I have a question. It is not clear which PicAxe chip was used with the HMC5883L. Was it the 08M2?
    The age of the thread is not an issue, but the length of it is. Which part of the 60+ posts is of interest to you? It's usually best to say how you want to use the sensor.

    The sensor in question uses an I2C bus, so in principle any (recent) PICaxe could be used (including the 08M2). Then it depends how the acquired data is to be used, or what (else) you want the PICaxe to do. If the data needs a moderate amount of mathematical processing then an X2 chip might be more appropriate, but more complex calculations can be done even with an 08M2, by using a few dedicated subroutines.

    Cheers, Alan.

  8. #68
    New Member
    Join Date
    Nov 2017
    Location
    United Kingdom
    Posts
    5

    Default

    Quote Originally Posted by AllyCat View Post
    Hi,

    The age of the thread is not an issue, but the length of it is. Which part of the 60+ posts is of interest to you? It's usually best to say how you want to use the sensor.

    The sensor in question uses an I2C bus, so in principle any (recent) PICaxe could be used (including the 08M2). Then it depends on how the acquired data is to be used, or what (else) you want the PICaxe to do. If the data needs a moderate amount of mathematical processing then an X2 chip might be more appropriate, but more complex calculations can be done even with an 08M2, by using a few dedicated subroutines.

    Cheers, Alan.

    Thanks Alan

    I am wanting to make an extremely small sensor something that can be hidden in the hand that will activate a small coin vibration motor. it needs to detect a small magnet (about the size of a £1 coin) from approx 12".

    Does the original poster still have a schematic for this?

  9. #69
    Senior Member
    Join Date
    Feb 2012
    Location
    London
    Posts
    2,717

    Default

    Hi,

    Quote Originally Posted by Nelixuk2003 View Post
    ... small sensor something that can be hidden in the hand ......to detect a small magnet (about the size of a £1 coin) from approx 12".
    I believe the original post concerned a fixed detector to monitor changes in the Earth's magnet field, caused by the presence of a large magnetic object such as a motor car. So I believe your requirement is rather different.

    In particular, if the detector is "hidden" in a hand then presumably the direction of the Earth's magnetic field will change as the hand is moved? Therefore your magnet needs to generate a field which is "large" compared with the Earth's magnetic field (or at least any directional changes in it).

    A Pound coin is physically quite large compared with some available Neodymium magnets, but (at best) you have to contend with the "Inverse Square Law", e.g. moving the sensor ten times further away makes the field one hundred times smaller. In practice, it might be even worse, because at "large" distances (compared with the size of the magnet) the North and South poles "cancel each other out" and you'd see no detectable magnetic field at all.

    The basic schematic need be no more than four wires (Supply, Ground, SDA and SCL) between the sensor and PICaxe (plus a battery and supply decoupling capacitor, etc.), but the main design will be concerned with the magnetic "circuit", which might need much "trial and error".

    Obviously it depends on the exact application requirements, but if I was developing something that I was fairly sure would work, then I'd be considering an "active" electromagnetic transmitter, i.e. a tiny battery, coil (antenna) and oscillator (which might be anything from a few Hz up to many MHz, depending on the "sensor") fitted into the space of a "Pound Coin".

    Cheers, Alan.

  10. #70
    Member
    Join Date
    Mar 2014
    Location
    United Kingdom
    Posts
    70

    Default

    Quote Originally Posted by Nelixuk2003 View Post
    I am wanting to make an extremely small sensor something that can be hidden in the hand that will activate a small coin vibration motor. it needs to detect a small magnet (about the size of a £1 coin) from approx 12".
    If it helps, I recently got 10 off SS49E magnetic sensors for 94p (inc. P&P) from a Chinese supplier via a well known auction site. As they're in a TO92 case, they're very small but do need added circuitry to do anything useful.

    Basically, they provide a mid-level voltage output (typically 2.5V on a 5V supply) which varies up or down depending on the field strength and polarity, i.e. a north pole will deviate the signal one way, and a south pole the other way.

    Coupled to a small CMOS op-amp configured as an amplifier, you could make quite a cheap but sensitive basic magnetometer.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •