finally moving a fixed distance to zero it. This isn’t
perfect, as it sometimes overshoots the mark, but
an error of 1mm on the pen is OK in this case.
FIGURING OUT THE CLOTH BACKING
The sequin cloth consists of shiny sequin discs
that are stitched to a fabric backing. The sequins,
colored pink on one side and blue on the other,
flip easily with a finger when they’re mounted
on a T-shirt or a bag with a soft backing. But the
moment I mounted it on a cylinder it stopped
flipping as the discs got over-constrained by the
hard backing. First I tried a ribbed structure as
a backing with the fabric stretched on it. This
worked but was very complicated to construct.
Finally I figured it out that a simpler way was to
just add a 3mm sponge foam layer as a backing
to the cloth to give the sequins the freedom to flip
(Figure
D
).
THE TIP OF THE PEN
The tip of the pen was very tricky to figure out.
Getting a material to act like the tip of a human
finger is not simple. The disks are very slippery
and need just the right friction to flip them.The
final solution was a tip made of TPU plastic
(thermoplastic polyurethane) with a split hook
(Figure
E
).
WHAT’S NEXT
Sequino is still a prototype, although I’ve tried to
use maximum off-the-shelf components. It can
be built by an advanced user — the 3D printing is
a bit tricky and the optical sensors need a little bit
of work. I intend to make it a kit sometime soon,
and to share an Instructable, but I’ve been a bit
stuck as I am in Beijing and things have been held
up due to the outbreak!
PROJECTS: Sequin Rewrite Clock
Sponge backing
Optical sensor and belt mark
Ribbed backing
TPU pen tip
Watch the Sequino clock in action
at youtu.be/6jpsiIsMG8U.
98 make.co
C
D
E
1. TORLO
The Torlo was born out of the idea of using a
simple oscillating motor as a power source.
The voice coil of a scrap laptop hard drive fit the
bill nicely; it’s pulsed by an ATtiny2313 every 2
seconds to drive the balance wheel, which pushes
a cam and a ratchet to turn the clock 2 seconds
further. The rest of the clock is a simple drive
train driving the minute and hour rings, which
display the time.
2. EDGYTOKEI
The Edgytokei (“edge clock”) is inspired by
Japanese nunchucks — just a pair of arms
displaying the time by balancing themselves on
edge. Both arms are of equal length, as their
roles change with different hours of the day. The
fulcrum of the clock flips from the center to the
left or right every quarter hour, so that the clock
can always stand on edge. Both arms have LEDs;
whichever one represents the hours lights up.
3. DOODLE CLOCK #2
I built my first Doodle Clock with marker pens as
a joke, but watching it work was so mesmerizing
that I wanted it to be a practical desk clock.
The problem was the markers dried up after 30
minutes. So the solution I found was magnetic
writing boards made for children. I used 2mm
cylindrical magnets inside a solenoid to write
and erase the text, and small geared steppers to
make the clock silent and smooth. The clock is
run by an ATmega644p with Arduino bootloader,
the motors are run by the standard StepStick
drivers, and the coils are run by a 1293DD dual
H-bridge. The kinematics for the arm were solved
by a user on the RepRap forum!
4. HOLOCLOCK
My first 3D printed clock, based on a single
geared stepper motor I found in surplus, 10 for a
dollar. It’s driven by an ATtiny2313 and ULN2803
Darlington circuit, with the code written in
Arduino IDE. The ATtiny pulses the motor every
minute to move a gear train, which in turn moves
the minute ring and hour ring. I still sell it as a kit
at tindie.com/products/ekaggrat/3d-printed-
holo-clock.
5. SPIRE
The spiral form of this clock unfolds and folds
in the rhythm of a Japanese fan. This project,
co-designed with Darshan Soni, won a Red Dot
Design Award.
1
3 4 5
2
99
makeprojects.com
More of Kalsi’s Clocks
You can find them all at ekaggrat.com and get build details for most of them at hackaday.io/ekaggrat.
A capacitor stores electricity,
as you will see in this experiment
PROJECTS:
Easy Electronics
Comprehending
Capacitors
Written and illustrated by Charles Platt
100 make.co
Adobe Stock - 55ohms
101
makeprojects.com
Some capacitors have colored cans.
Others don’t. The color is not important.
I wrote my book Easy Electronics to help
beginners get acquainted with electronics more
simply, quickly, and affordably than ever before.
A dozen hands-on experiments show you the
basics, and each one takes half an hour or less.
You won’t need any tools at all.
You will need: AA batteries (3) with holder,
alligator jumper wires (3), 470µF capacitor, 100µF
c a p a c i t o r , 1 k Ω r e s i s t o r , t h r o u g h - h o l e 5m m LED,
S PDT s l i d e s w i t c h .
EXPERIMENT:
T h e t y p e o f c a p a c i t o r s h o w n h e r e i s c a l l e d
electrolytic. It s s t o r a g e c a p a c i t y , k n o w n a s
capacitance, i s 4 7 0 µ F —b u t I’ l l e x p l a i n t h a t i n a
m o m e n t . 50 V i s i t s m a x i m u m v o l t a g e , b u t f o r t h i s
e x p e r i m e n t , a r a t i n g o f 1 0 V o r h i g h e r i s o k a y .
T h e s h o r t l e a d i s t h e n e g a t i v e s i d e , a l s o
i d e n t i f i e d w i t h m i n u s s i g n s . T h a t ’ s b e c a u s e
t h i s c a p a c i t o r h a s polarity — n e v e r c o n n e c t a n
e l e c t r o l y t i c c a p a c i t o r t o a p o w e r s u p p l y t h e w r o n g
w a y a r o u n d .
A d d t h e 1 K r e s i s t o r a n d t h e LED, w i t h t h e
n e g a t i v e s i d e o f t h e LED s h a r i n g t h e n e g a t i v e l e g
o f t h e c a p a c i t o r .
No w m o v e t h e s w i t c h t o t h e l o w e r - r i g h t . T h e
c a p a c i t o r d i s c h a r g e s i t s e l f t h r o u g h t h e LED.
Mo v e t h e s w i t c h t o t h e u p p e r - l e f t a n d w a i t 5
s e c o n d s f o r t h e c a p a c i t o r t o r e c h a r g e . No w y o u
c a n d i s c h a r g e i t a g a i n a n d l i g h t t h e LED a g a i n !
Y o u c a n b u i l d t h i s c i r c u i t i n t w o s t e p s . T h i s p a r t
j u s t c h a r g e s t h e c a p a c i t o r w i t h e l e c t r i c i t y w h e n
t h e s l i d e s w i t c h m o v e s t o u p p e r - l e f t .
S o m e o f t h e v o l t a g e f r o m t h e b a t t e r y
t r a n s f e r s t o t h e c a p a c i t o r , a l t h o u g h y o u c a n ’ t
s e e a n y s i g n o f i t y e t .
CHARLES PLATT is the author of
Make: Electronics, an introductory
guide for all ages, its sequel
Make: More Electronics, and the
3-volume Encyclopedia of Electronic
Components. All these and his
workshop guide, Make: Tools, are
available at makershed.com/platt.
If this diagram looks complicated to you,
try sketching a copy of it, replacing the
alligator wires with simple lines to connect
the components.
PROJECTS: Easy Electronics
102 make.co
HOW DOES IT WORK?
Inside the capacitor you used are two pieces of
metal film known as plates. They are separated
by paste called an electrolyte, which is why this
capacitor is called electrolytic.
When electrons flow into one plate, they try to
create an equal, opposite charge on the other.
You can think of the plates as having positive and
negative charges that attract each other.
TIMING
The 1K resistor was needed because you charged
the capacitor with 4.5V from the battery pack, and
the LED can only handle about 1.8V. The resistor
prevents the LED from being damaged.
The resistor also controls how fast the
capacitor discharges. Substitute a 10K resistor
(brown, black, orange) and the LED is dimmer
than before and takes much longer to fade out.
Here’s another thing to try. Go back to using
the 1K resistor. Remove the 470µF capacitor and
substitute a 100µF capacitor. Push the switch to
and fro, and now the LED lights up very briefly.
Electricity moves fast, but a capacitor and a
resistor can make things happen slowly.
CERAMICS
Capacitors such as the one shown above
a r e l e s s t h a n ⁄" w i d e . T h e y a r e d i p p e d i n a
ceramic c o m p o u n d .
Mo s t c e r a m i c c a p a c i t o r s d o n o t h a v e p o l a r i t y .
Ma n y c e r a m i c c a p a c i t o r s h a v e a c o d e p r i n t e d
o n t h e m i n s t e a d o f t h e i r a c t u a l c a p a c i t a n c e .
S o m e c e r a m i c c a p a c i t o r s a r e s h a p e d l i k e
c i r c u l a r d i s c s .
I n s i m p l e c i r c u i t s o f t h e t y p e y o u h a v e b e e n
b u i l d i n g , u s u a l l y y o u c a n s u b s t i t u t e a c e r a m i c
i n s t e a d o f a n e l e c t r o l y t i c i f y o u w i s h . No t e t h a t f o r
v a l u e s a r o u n d 1 0 F a n d a b o v e , c e r a m i c s m a y b e
m o r e e xp e n s i v e .
UNITS
C a p a c i t a n c e i s m e a s u r e d i n farads, a b b r e v i a t e d
w i t h l e t t e r F . Bu t a 1 F c a p a c i t o r i s v e r y l a r g e . I n
h o b b y e l e c t r o n i c s w e m o s t l y u s e c a p a c i t o r s r a t e d
i n m i c r o f a r a d s , a b b r e v i a t e d F . T h e s y m b o l i s
t h e G r e e k l e t t e r m u , b u t o f t e n F i s p r i n t e d a s u F .
T h e r e a r e 1 , 0 0 0 , 0 0 0 m i c r o f a r a d s i n 1 f a r a d ,
1 , 0 0 0 n a n o f a r a d s ( n F ) i n 1 m i c r o f a r a d , a n d 1 , 0 0 0
p i c o f a r a d s ( p F ) i n 1 n a n o f a r a d .
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.