====== Parts ======
The 74HC595 shift register has a maximum sink current of aprox 25mA which is too small.  Another choice might be the HEF4794 which is know as an //8-stage shift-and-store register LED driver//, however, this also seems to have a relatively low maximum sink current.

I found reference (([[http://www.instructables.com/id/SRJJMJUFH9HU7GQ/]])) to the MIC2981 which is a //high-voltage high-current source driver array//.  I think this can be used to drive the coils with the shift register as the input (possibly using the 74HC595).

The clear winner looks to be the TPIC6B595.  This is a high-power medium-current shift register which has a continuous sink of 150mA with a 500mA limit!!!  Since each coil only needs a short pulse of current, this chip might be ideal.  The absolute minimum current required to flip a disc needs to be determined.

====== Flip single dot ======
Found reference (([[http://pubs.drdc.gc.ca/PDFS/zbc77/p56839.pdf]])) in a document describing a land mine that uses flip disc displays.  The document claims the coils require a 250mA pulse for at least 1.5ms.

In my testing, 250mA from a 5v source works.

====== Weird chip ======
{{:notes:somechip.jpg?100}}

Possibly a gate, flipflop, transistor or mosfet

With help from liggyman on #hacklabto this looks to be a transistor in a SOT-323 package (NPN?).


====== Stuff to read up on ======
[[http://en.wikipedia.org/wiki/H-bridge|H-Bridge]],
[[http://en.wikipedia.org/wiki/Gate_(transistor)|Field-effect transistor]],
[[http://en.wikipedia.org/wiki/Flip-flop_(electronics)|Flip-flop]],
[[http://en.wikipedia.org/wiki/Bipolar_junction_transistor|Bipolar junction transistor]],
[[http://en.wikipedia.org/wiki/Transistor|NPN transistor]]

====== Links ======
  * [[http://en.wikipedia.org/wiki/Flip-disc_display]]
  * [[http://www.instructables.com/id/LED-matrix-using-shift-registers/]]
  * [[http://www.flipdots.com/EN/electromagnetic_displays/principle_of_operations/index.html]]