WARNING
This is not a toy. It is an educational kit and must be used under
adult supervision. This product is not suitable for children under
3 years. It contains sharp or small parts that could be dangerous
for young children.
!
Care
Needed
Manufactured and Supplied by Mindsets
Copyright © Mindsets (UK) Limited, 2011
The Earth Clock is one of a number of innovative educational products designed at
Middlesex University to interest young people in science and technology. Please ask your
supplier for more details.
Ea r t h
Clock
Earth clock
What to do next
Welcome to the fascinating world of timekeeping. You have just
bought a high-tech electronic clock that gets all of its power
from ordinary earth! You will never need expensive batteries –
and you will be able to run your clock using other unlikely
materials.
Soil is an ideal material for your earth clock, but it must be wet. You
could run the clock from a pot plant but the pairs of metal strips
must be at least 5cm apart. If the soil gets too dry, the clock stops
working and tells you that the plant must be watered.
Avoiding the use of batteries is environmentally friendly. All the
energy and materials that go into the battery are saved, and
there is nothing to dispose of when the battery is used
up.
About timekeeping
From the earliest days, people have used the
position of the sun to tell the time. We still use
sundials today; a thin piece of metal casts a
shadow on to a scale, so that we can read off
the hours.
In the Greek and Roman world, other things
were also used for timekeeping. These included
burning candles with hourly markings down the
side and water clocks. Water clocks consist of a
container with a small hole at the bottom. The
falling level measures passing time as water slowly leaks out.
Mechanical clocks were invented during the Middle
Ages. These used weights and (later) springs to turn
hands on a dial. The important part of a mechanical
clock is the escapement that produces the ‘tick tock’
sound. This releases the energy stored in the falling
weight or unwinding spring in tiny regular amounts.
Over hundreds of years, mechanical clocks and
watches became far more accurate – and we still
use them today.
Any other material that is slightly acidic can be made into a battery
for your clock. Newspapers and cheap books use paper that has a
high acid content. That is why they go brown over time. The acid
attacks the paper. If you tear and mash up some old newspaper in
water, you can run you clock from that instead of earth. Make sure
the newspaper is well mixed up – like mashed potato.
You can try out all kinds of other materials and liquids to see if they
give you a voltage. If you push the pairs of metal strips into fruits
such as lemons or oranges, the acidic juice will work. Lemon juice
squeezed into two small pots will work well. If you are using earth
and it doesn’t work very well, then you can make it more acidic by
adding a small amount of fruit juice or vinegar. Most fizzy drinks are
slightly acidic, but will not work as well when ‘flat’.
NOTE: After some time, the metal strips will be ‘eaten’ by the
chemical action. If the clock stops working, clean the strips with
abrasive paper or wire wool.
Setting the clock
In the last century, electronic clocks and
watches were developed. These use an
electronic circuit instead of a mechanism, and
they show time with either moving hands
(analogue display) or numbers on a screen
(digital display). They are much more accurate
than most mechanical clocks and watches.
1.
Press the centre button on the rear of the clock twice and the clock
will enter the setting mode – the display will flash between time and
date.
2.
Press the centre button again and the month will be displayed. This
can be changed by pressing either of the outer buttons.
3.
Press the centre button again and the day will be displayed, change
as before.
Your clock has a digital display and is accurate to around two
seconds per week. It requires only a small electrical current to
work.
4.
Press the centre button again and the hour and AM or PM will be
displayed, change as before ensuring that AM or PM is correct.
Getting electricity from earth
5.
Press the centre button for minute setting.
6.
Press the centre button again and clock will be in run mode,
indicated by flashing dots.
The pressing of either outer buttons will show the date.
Over two hundred years ago, a scientist called Volta discovered a
way of producing electricity using two different metals and weak
acid. In the world’s first battery (called a voltaic pile after Volta), he
placed silver and zinc disks either side of paper soaked in weak acid
(eg vinegar). This produced electricity. To produce greater voltage,
he connected several pairs of metal disks together in series.
Your earth battery uses pairs of two different metals: copper and
zinc. If you dip them into acid they will produce electricity – about
0.5 volts. We now understand that a special chemical reaction
takes place between the metals and the acid. Your clock needs
about 1 volt, so if you connect two pairs of metals in series (like
Volta did with his disks) and dip them in vinegar you would get 0.5
volt + 0.5 volt = 1 volt.
So, why use earth? Most soil is either slightly acidic or slightly
alkaline (alkaline is the opposite of acidic). In fact, you will find
that most wet soils work very well.
How to assemble the earth clock
4. Cut the plastic covering off
the ends of the wires from the
clock and screw them into the
connecting blocks. Make sure
the wires are connected the
right way around as shown.
1. If you would like your clock to display a
graphic you may design your own insert. The
size of the insert should be 35 x 55mm. Slide
the graphic into the top of the clock.
2. Screw the metal strips into the connecting
blocks as shown.
copper strip
copper strip
zinc
(silver)
strip
zinc
(silver)
strip
5. Put some damp mud into the
containers provided. Carefully
press the metal strips into the
mud, taking care that the strips
do not touch each other.
The clock should now start to
work.
3. Screw the loose metal wire into the
connecting blocks as shown. Make sure it
connects a zinc strip to a copper strip.
Note: If the mud dries out, the clock will stop working – keep
the mud moist by adding an occasional drop of water.
If the clock stops working, remove the metal strips and clean
them with an abrasive cleaner. This will remove the layer of
oxide that has built up.
black
wire
red
wire