title: Android SDK keep NFC on
body: <p>I am using the NFC capability of an android phone to induce a small amount of current in a coil to charge up a capacitor. currently i am using the NFC-V application in the app store (<a href="http://www2.st.com/content/st_com/en/products/embedded-software/st25-nfc-rfid-software/stsw-m24lr012.html" rel="nofollow">source code available here</a>) to achieve this. What I found is the phone can charge up the capacitor easily when i constantly remove the board and place it near the field again, but if i leave the board sationaly in the field it only successfully charges about 30% of the time (maintains 3.3V when sucessful). </p>
  
  <p>I believe this could be due to something in android API which turns off the magnetic field once a tag is discovered?</p>
  
  <p>Could someone explain what the NFC API does once it discovers a tag (i.e does it turn off the magnetic feild once detected and turn it back on when removed?)</p>
  
  <p>further more is there a way to keep the magnetic field constantly on using the NFC api?</p>