Magnetometer

Comments

• Bruce Bates Posts: 3,045

  2005-06-07 16:32 edited 2005-06-07 16:32

  Erik -
  
  You can obtain the appropriate datasheet(s) for the Honeywell magnetometers in question from this link: http://www.magneticsensors.com/datasheets.html . Those datasheeets should answer most, if not all, of your questions.
  
  I glanced quickly at the datasheets and it appears you will need an external ADC, and possibly an external clock source as well. There are some very good examples of how to provide the necessary external equipment. Insofar as the Stamp interfacing is concerned, it will probably be with SHIFTIN or I2CIN from what I can gather.
  
  Regards,
  
  Bruce Bates
• ErikdS Posts: 37

  2005-06-07 18:25 edited 2005-06-07 18:25

  English not being my mothertongue, ADC is analog to digital convertor?
• Bruce Bates Posts: 3,045

  2005-06-07 18:37 edited 2005-06-07 18:37

  Erik -
  
  Exactly correct, ADC is shorthand for analog to digital converter, as DAC is digital to analog converter. You don't need to know English, see
  
  Bruce
• dechief michel Posts: 75

  2005-06-09 19:24 edited 2005-06-09 19:24

  Erik,
  if you are looking to interface with a adc chip, give a look in to WAM(download for free from parallax) and specifically about
  the ADC0831 8 bit analog to digital converter (give you 256 resolution on 5 volt). Very easy to interface.
  Sorry too i'm french talking(from Belgium)
  Regards and enjoy your project with Parallax users
  Michel
• ErikdS Posts: 37

  2005-06-09 19:39 edited 2005-06-09 19:39

  Ah yes Michel,
  
  but I'm trying to build a really sensitive magnetometer and the IC I'd settle for right now has a maximum field range of up to 60000 nanoTesla (earth's magnetic field being 5000 nT) and a resolution of only 3nT, so I'm quite sure 8 bit resolution will NOT save the deal, I fear I may need at least 16 bit, or even better.
• jackinnj Posts: 5

  2005-06-13 22:09 edited 2005-06-13 22:09

  If it is "really sensitive" then you should be looking for a high quality differential amplifier on the bridge circuit and a 16 bit ADC. On the Honeywell site the AMP04 is recommended -- this is a high quality single supply differential amplifier from Analog Devices. Your best bet is going to be to prototype this on a printed circuit board with a ground plane and adequate bypassing of the amplifier etc. Read up on low noise circuits on the Analog Devices website www.analog.com
• John Kauffman Posts: 653

  2005-07-13 17:13 edited 2005-07-13 17:13

  My son built a magnetometer when he was young from some plans in Scientific American series of articles for the Ameteur Scientist. It was more of a mechanical device then electronic, but might have some use to you.
  
  He glued two timy (2 mm) rare-earth magnets (cheap because used to make hearing aids) on either side of the center of a vertical thread of about 10 cm and then glued a bit (3 mm diameter) of mirror to one magnet. He lined a laser pointer on the mirror and looked at where the laser dot reflected on the far wall. In a small magnetic field the magnets-mirror would rotate very slightly and that rotation was amplified by the distance of the laser point reflection.
  
  He saw a 0.5 meter swing in the laser dot when using a 1.5 volt battery in a short circuit through a 24 gauge wire that was about 5 cm from the magnets.
• ErikdS Posts: 37

  2005-07-14 11:35 edited 2005-07-14 11:35

  Ouch, Jackinnj,
  
  you lost me there already. What do I need the differential amplifier for?
  There's one chip giving me analog output, I thought I could feed that to the ADC, and the ADC to the BS2?
  (I think it may start to dawn on me as I'm writing, but lay it out for me again please, I'm a bit of a dummy)
  
  Greetings,
  
  Erik