siliconchip.com.au Australia’s electronics magazine April 2019 2719111181191111811911118119111181TOP VIEW OF COIL PCB UNDERSIDE VIEW OF COIL PCBCON7P CON5PCON8P CON6P
COM
P11P10
P13P12
P15 P14P9P3 P2
P5P6 P1
P4P7P8P1 COIL P1 COILP4 COIL P4 COILP7 COIL P7 COILP10 COIL P10 COILP13 COIL P13 COILP2 COIL P2 COILP5 COIL P5 COILP8 COIL P8 COILP11 COIL P11 COILP14 COIL P14 COILP3 COIL P3 COILP6 COIL P6 COILP9 COIL P9 COILP12 COIL P12 COILP15 COIL P15 COILCON7P(1) (2) (4)(8) (16) (32)(64) (128) (256)(512) (1024) (2048)(4096) (8192) (16384)19111181191111811911118119111181TOP VIEW OF COIL PCB UNDERSIDE VIEW OF COIL PCBCON7P CON5PCON8P CON6P
COM
P11P10
P13P12
P15 P14P9P3 P2
P5P6 P1
P4P7P8P1 COIL P1 COILP4 COIL P4 COILP7 COIL P7 COILP10 COIL P10 COIL
P13 COIL P13 COIL
P2 COIL P2 COILP5 COIL P5 COILP8 COIL P8 COILP11 COIL P11 COILP14 COIL P14 COILP3 COIL P3 COILP6 COIL P6 COILP9 COIL P9 COILP12 COIL P12 COILP15 COIL P15 COILCON7P(1) (2) (4)(8) (16) (32)(64) (128) (256)(512) (1024) (2048)(4096) (8192) (16384)Fig.4: the coil board. Each coil is made from copper on both sides of the board.
Solder four 2x2-pin SMD headers to the back side of this board, as shown.
The only parts soldered to the top side of the board are the six frame strips
which hold the pixel flaps in place. Add numbers in parentheses for each pixel
that you want to be ‘on’ to determine the code used to produce a particular
character. For example, 2+8+32 = 42 will give you a caret (^) on the display.ommend that you leave it longer than
suggested by the manufacturer to en-
sure it is fully cured. If it is still sticky,
it may gum up the mechanism and
make handling difficult.
If you wish to change the colour of
the flaps, after the resin has cured is an
ideal time. A thin coat of paint should
be used to ensure that the flaps do not
become too heavy. You could use spray
paint, one colour on one side, and a
second colour on the other side.
You could apply the same colours to
the coil PCB, although this will need
masking to ensure the colours are kept
separate.
However, we think most construc-
tors will be happy with the black and
white as supplied, since it provides
good contrast under just about any
lighting conditions.
Note that if you are building mul-
tiple displays to be ganged together,
it’s a good idea to ensure that the mag-
netic polarity is consistent across all
the displays, to avoid extra software
complexity.
If different characters have different
pixel black/white orientation, this will
need to be programmed into the soft-
ware, so that it can give a consistent
display across characters.Building the frame
You will need six frame elements
to build one fifteen-pixel display. But
note that if you are going to be stack-
ing two frames vertically, you will only
need eleven in total; one frame will be
shared between two boards. The frame
pieces are cut from a 72.5 x 75mm PCB
which contains eight separate frame1911118419111184C+CON3CON120191kW19111184 RevCFlipdot Display Driver PCB12VGND12VGND /5V GND DLTCK EN3.3 GNDDLTCKEN33Fm1000 mFIC174HC595IC174HC595IC274HC595IC274HC595IC3LIC3L293D293DIC4LIC4L293D293D IC6LIC6L293D293DIC5LIC5L293D293DCOCON4N4CON2
CON2CON5CON6CON7CON8/5V 3.^3Fig.5: use this PCB overlay diagram and the photo above as a guide to assembling the driver board. Note the location
of the headers for CON1 - CON4 and the orientation of the ICs. The two capacitors will need to be laid over to sit under
the coil PCB. The female headers are convenient for using jumper wires to a Micromite or Arduino, although you may
substitute anything that suits. At right is the Flipdot display main PCB – it may not be immediately obvious that the
circles on this board are in fact coils (see inset) which are responsible for “flipping” the “pixel” either white or black.