PPA – debugging

You’ve turned on your Personal Particle Accelerator, but aren’t getting the results you want ?  First, try the basic checklist:

  1. Completed the construction,
  2. Read the safety advice
  3. Performed the commissioning tests
  4. Attempted starting the PPA

ok, here’s the next level of detail:

The ball rolls to a stop, apparently unaffected by the electromagnets:

  1. Confirm the second-from-the-end LED on the led bargraph is consistently illuminated.  This LED indicates the electromagnets are enabled… without it, nothing will happen !
  2. Check you are supplying between 12V DC and 20V DC.
  3. Does the LED bar graph show sequential activation of electromagnets ?  If yes, then there is some problem with the output board or the electromagnets.  If no, the Arduino is not sending an output pulse to the Electromagnets.  Check whether any photogate (IRPS) signals are reaching the Arduino by connecting a CRO to Arduino I/O socket 2 (note: as pins start from zero, socket 2 is the third position).  If there are no pulses on socket 2 as the ball rotates, then there is a problem with the input board, or the IRPS.  If there are pulses on socket 2 as the ball rotates, then check whether the Arduino program is configured correctly.

Rotation continues for a while, but is not sustained

  1. Too much friction is slowing the ball down –
    * either the ball is too rough (possible if using a paint covered ball).  Test by using a smooth ball bearing.
    * there is some obstruction in the tube which is providing frictional forces slowing the ball down.  Look carefully to find the debris.  Uncouple the tube and hold vertically so the debris falls out.  If necessary gently probe with a something like a knitting needle, being careful not to scratch the inside surface.
    * the point where the two ends of the tube are joined is problematic – typically this results in irregular rotation, and noise as the ball hits the gap between the tubes.  Solution is to carefully push the two ends of the tube to cleanly abut eachother
  2. You need to calibrate your electromagnet pulses – this occurs when the electromagnets are pulsing, but their timing is not suited to your PPA’s exact geometry
  3. Check that the output board’s last LED in the led bar is NOT on.  It is a SAFETY interlock circuit, and has been activated because the pulses from the Arduino were deemed unsafe.  See design documentation, or contact me by email.


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