Download Publishing Information Safety Notes for Parents and Children

Publishing Information
© 2016 Franzis Verlag GmbH, Richard-Reitzner-Allee 2,
85540 Haar bei München • www.elo-web.de
Author: Burkhard Kainka
Idea/concept: Michael Büge, Burkhard Kainka
Editing: Jenny Pfeiffer
Art & Design Cover: www.ideehochzwei.de
Layout & Composition: Nelli Ferderer • [email protected]
ISBN 978-3-645-10212-4
2016/01
Photo Credits
Drawings created with http://fritzing.org/
All rights reserved, including photomechanical reproduction and storage in electronic media. The creation and distribution of copies on paper, on
data media or on the Internet, especially as PDF, is permitted only with the express approval of the publisher; violators will be prosecuted.
Most of the product designations as well as company names and company logos named in this work are as a rule also simultaneously
registered trademarks and should be considered as such. In the main, the publisher follows the manufacturer's spelling for the product
designations.
All circuits shown in this book were developed, reviewed and tested with the greatest possible care. Nevertheless, errors in the book cannot be
completely ruled out. In cases of malice or gross negligence, the publisher and author are liable according to the statutory regulations.
Otherwise, the publisher and author are liable for injury to life, limb or health or for the culpable violation of essential contractual obligations only
according to the Product Liability Act. The claim for damages for the violation of essential contractual obligations is limited to the foreseeable
damages typical of the contract unless a case of mandatory liability according to the Product Liability Act is present.
This product was manufactured in accordance with the applicable European guidelines and thus bears the CE mark. The intended use is described in the accompanying instructions. In the case of any other use or change to the product, you alone are responsible for the adherence to
the applicable rules. Therefore, build the circuits precisely as described in the instructions. The product may be passed on only together with the
instructions and this notice. The symbol of the struck-through rubbish bin means that this product must be taken to the recycling as electronic
scrap separately from the household waste. Your municipal administration can tell you where to find the nearest free collection point.
Safety Notes for Parents and Children
Attention!
Never carry out experiments on mains sockets! The 230 volts of the mains supply are a lethal hazard! All experiments of
this experimenter package must be carried out only with the safe battery voltage of 9 volts. Then there's no danger if you
touch the parts that conduct electricity.
Please tell your child explicitly to read all instructions and safety notes and to be ready to look things up. Notes and rules
for construction of craft projects absolutely must be observed.
Attention!
Eye protection and LEDs: Never look directly into an LED from a short distance, since a direct look can cause retinal damage! This applies especially for bright LEDs in clear housing and particularly for power LEDs. With white, blue, violet and
ultraviolet LEDs, the apparent brightness gives a false impression of the actual danger for your eyes. Special care is required when using collecting lenses. Operate the LEDs as shown in the instructions, but not with higher voltages.
Attention!
Avoid short circuits! A direct connection between the negative and positive terminals absolutely must be avoided, because
wires and batteries can become hot in such a case and because the batteries then quickly become flat. In extreme cases,
wires can become burning hot and the battery can explode. There is a risk of fire and injury. Teach your children about
these dangers and supervise the experiments. If possible, use only normal zinc-carbon batteries (6F20), which provide a
low short circuit current and thus are less dangerous than alkali batteries (6RL61). Never use rechargeable batteries!
Attention!
Not suitable for children under the age of 3 years. There is a suffocation risk because small parts can be swallowed or
inhaled.
Attention!
Suitable only for children aged 8 years and up. Instructions for parents or other responsible persons are included and must
be observed. The packaging and instructions must be kept because they contain important information.
Attention!
Risk of injury! When using tools and when working with wood, metal and plastic, there is a risk of injury. Pay attention to
the age and experience level of your child. Help out with difficult or dangerous steps. Check the safety of the home-made
toys and pay attention to a risk of injury from sharp corners while playing. If necessary, carry out some post-processing; file
off sharp edges and deburr drilled holes or cut edges.
Hello, knowledge-hungry folks!
In this calendar, 24 exciting projects with electronic components are waiting for you. You'll also frequently find info
boxes that explain why the tests work the way they do. If that's too hard for you at the beginning, you can also just
carry out the test for starters. You'll see: after a while, you'll understand the technical relationships almost automatically!
1
Your First DIY LED Lamp
Behind the first door you'll find: a breadboard, a battery clip, a switch, a fuse, a light diode (LED) and a resistor.
Make yourself a little LED lamp! Granted, it's not particularly bright, but it already has a switch and all the important
things you'll also be using in the experiments that follow. In this picture, you see in which holes on the breadboard
that you need to plug the components into.
You can secure the battery clip's connection cable with tape on the edge of the breadboard or stick it underneath
through the board's mounting holes. To do this, you first have to puncture the adhesive film on the bottom with a
needle. It's best to get an adult's help to do this.
There are numbers printed on the breadboard for the positions from left to right and letters for the positions from
top to bottom – you might recognise them from maps.
To plug the components into the breadboard, it's best to take a small pair of flat pliers and insert the wires precisely
from above. Pay attention to the correct position of the connections.
The fuse and the switch will stay in the same position until the last test and don't have to be taken out anymore.
With the LED, you need to pay attention to the assembly direction. The shorter wire is the negative terminal (the
cathode C); the longer wire is the positive terminal (the anode A). From the outside, you can recognise the larger
bracket for the LED crystal on the cathode side. There's also a small flat place on this side of the housing. That's
also the case for the coloured LEDs. In addition, for the white LED, there's a fluorescent yellow colour that covers
the LED crystal. There are coloured LEDs that look almost exactly the same from the outside. But looking at it from
the front through the lens helps you recognise the white LED at any time, even when it's switched off.
The resistor can be installed in any direction. There are coloured rings on it (yellow, purple, red and gold), which
have an important meaning. In this case, they say that the resistor is 4700 Ohm (4700 ).
The battery clip should be installedonto the battery only when everything has been completely assembled and
checked precisely. Then slide the switch  1 to the ON position. Now the light diode (LED) should light up white. The
first little LED lamp is finished!
Attention
Never connect the positive terminal to the negative terminal of the battery because then too much current flows. Your battery will quickly become unusable in that case. In extreme cases, the battery can even explode or wires could become hot
enough to glow and burn.
If it doesn't work, you may have installed the LED the wrong way round. Also check all the other connections and
compare everything exactly with the layout picture.
Circuit Diagrams
A circuit diagram shows the connections of the components in a simplified manner. At first, it might be harder than our
layout picture, since the actual components look different. Once you've got used to it, though, you'll even understand
much better how everything goes together with a circuit diagram.
The battery consists of six battery cells with 1.5 V each. The longer line stands for the positive terminal. The fuse is shown
as a little box with a wire. The switch shows an open connection, so it's already in the "Off" position. The resistor is depicted as a box. And the LED contains an arrow that shows the direction of the current. The two little arrows are supposed
to represent the light that's generated.
In this case, you'll easily recognise that all components form a closed path. That's called a circuit. The path is broken at
only one point, at the already open switch. Circuit diagrams will constantly be shown in the tests that follow. They can help
you understand everything, even better.
2
More Light!
Your first LED lamp wasn't very bright yet. However, behind Door Number 2, you'll find another resistor. The first
resistor had 4.7 kΩ; this one has only 0.47 k (470 = 4.7 kOhm, short 4.7k) and thus lets much more current
through. Your lamp thus gets much brighter.
The Resistor Colour Code
Colour
Ring 1
1st Digit
black
Ring 2
2nd Digit
Ring 3
Multiplier
0
1
Ring 4
Tolerance
brown
1
1
10
1%
red
2
2
100
2%
orange
3
3
1000
yellow
4
4
10000
green
5
5
100000
blue
6
6
1000000
violet
7
7
10000000
grey
8
8
white
9
9
Gold
0.1
0.5%
5%
Silver
0.01
10%
Resistors and Their Coloured Rings
The coloured rings on the resistors represent numbers. They are read beginning with the ring that is closer to the edge of
the resistor. The first two rings stand for two digits, the third for added zeroes. Together they designate the resistance in
ohms. A fourth ring gives the precision. All resistors in this calendar have a gold ring. That means that the given value can
be 5% larger or smaller than stated by the coloured rings.
3
Switchable Brightness
On the third day, you'll find a cable with two small plugs in your calendar. With it, you can build a very special lamp
with which you can select the brightness.
More brightness is sometimes an advantage, but it also has a disadvantage: Namely, the energy of your battery is
used more quickly. That's why the second switch is there. When it's in the ON direction, more current flows and the
LED is brighter. The first switch continues to serve for the lower brightness. And there you have your very special
lamp with two brightness levels.
Actually, there are even three brightness levels. Switch 1 is responsible for the simple bright-ness and Switch 2 for
the tenfold brightness. But when both switches are on, you have eleven times the brightness. Try it once: Switch 2
is on, and Switch 1 is switched on and off alternately. The difference is very slight. Can you still detect it?
Voltage, Resistance and Current
The electrical voltage is measured in volts (V). The battery has 9 V. And one measures the resistance, as you already
know, in ohms (Ω) or kilohms (kΩ = 1000 Ω). But there's yet another very important unit of measurement. The strength of
the electrical current is measured in amperes (A) or, for very small current strengths, in milliamperes (mA = 1/1000 A).
You can calculate how much current flows through the LED when you know how much voltage there is directly at the battery and how much voltage is present at the LED. The battery has a voltage of 9 V. The LED consumes around 3 V. That
still leaves 6 V for the resistor. For the low brightness, you can figure as follows:
Current = Voltage / Resistance
Current = 6 V / 4700
Current = 0.0013 A = 1.3 mA
That's not much; only 1.3 mA flows, although the LED carries 20 mA. But the battery lasts a long time! It could deliver 2000
mA for one hour or 1 mA for 2000 hours. Or your lamp lights up for about 1500 hours with 1.3  mA, so for over two months.
For the greater brightness, you get to about ten times the current (13 mA) and so you're already closer to the permissible
limit of 20 mA. But the battery can handle that for only about 150 hours, that is, barely a week.
4
A Lamp with Two LEDs
Another white LED appears behind the fourth door. Install it in your lamp with everything else. The lamp thus becomes somewhat brighter. The brightness is already enough to read a book by at night. And again, there are two
brightness levels. You decide how much light is used.
Series Circuitry
With series circuitry, the same current flows through two or more consumers. It is a "unbranched electrical circuit" because
there's only one path. That means that the current strength is the same at every point.
Simplified circuit diagram of a series circuit
The voltage is distributed to the consumers in the circuit. In this case, there are two LEDs and a resistor. Each white LED
uses approximately 3 V. Two LEDs thus consume 6 V. And because the battery has 9 V, a voltage of 3 V is left over for
the resistor. So in this case, the battery voltage is distributed in equal amounts to three consumers. The energy consumption is distributed in exactly the same way. The resistor generates only some heat, but the LEDs generate the desired light.
Because only a third of the voltage is present at the resistor this time, only a third of the energy is "wasted." The circuit with
two LEDs in series is thus better than the one with only one LED, where two thirds is lost.
5
Connected in Parallel
Open the fifth door and take out another cable. With this, you can connect the LEDs in parallel. When you've set
everything up correctly, both LEDs light up.
Parallel Circuitry
This time you've built a parallel circuit, which is also called a "branched circuit." The current through the resistor distributes
itself to two LEDs. Half of the current flows through one LED, the other half through the other LED. A small test can prove
that: Remove the cable between both LEDs one time. One LED then goes out, but the other becomes brighter. In other
words, the entire current now flows through it.
Parallel circuit with two LEDs
6
Secret Light Signal
The sixth door hides a small push-button switch. When you push on the button, two contacts are connected. That's
exactly the right component for a signal lamp. You can use it to send secret messages. Your signal LED is operated with high brightness. In addition, there's an LED with a weaker steady light, which can be switched on using
Switch 1.
Morse Signals
7
Green Signals
May there be a different colour? In Compartment Number 7, you'll find a green LED. Install it instead of the white
signal LED. The light from this LED can be seen over even larger distances.
8
An Electrical Tester
Open the eighth door and take out another resistor. It has 10  kΩ (brown, black, orange) and should thus reduce the
current through the LED even more. Today you're building a tester with which you can check what objects can
conduct electrical current. For this purpose, there are two cables with test probes. You can touch any objects you
like with them. When the light goes on, you know that current is flowing through what you're touching.
You'll also find weak conductors: Touch both wires with your fingers; then you'll see a very weak light. Your body,
thus conducts some electricity. If you moisten your finger with water, more current flows. But that's not dangerous
because the battery has a voltage of only 9 V. At voltages above 48 V, by contrast, it can already be dangerous.
And at the mains voltage of 230 V, there's a risk of fatal shock! So you may touch wires only when you know for
sure that the voltage is small enough (less than 12 V).
In addition to a test object, the push button can also close the circuit. That helps to differentiate whether the object
you're testing is a very good conductor or a poor conductor.
Touch a conductor with the test cables so that the LED lights up. Now also push the button. Does the LED get even
brighter then? In that case, you're touching a weak conductor. But if you're testing a coin, for example, there will be no
difference because all metals are good conductors.
Touch a conductor with the test cables so that the LED lights up. Now also push the button. Does the LED get even
brighter then? In that case, you're touching a weak conductor. But if you're testing a coin, for example, there will be no
difference because all metals are good conductors.
Additional Test
Also test electrical components. The resistors from your calendar differ in how well they conduct the current. An LED conducts in only one direction. And you can even check whether an incandescent light bulb still works or has already burned
out.
9
Red Light
Behind Door Number 9, you'll find a red LED. It should now be connected in series to the green LED. The same
current flows through both. You already know that from Day 4, when two white LEDs were connected in series. But
which looks brighter, the red or the green LED? You can select brightness levels again by setting S1 or S2 to ON.
Additional Test
Try letting both LEDs shine on a piece of white paper. Where the coloured circles intersect, you should see the secondary
colour yellow.
10
A Colour Switcher
Open Door Number 10 and take out a 2.2 kΩ resistor (red, red, red). This time you should build a very special circuit: a green/red switcher. Every time you push the button, the red LED goes on and the green turns off.
When the switch contact is closed, it's actually only a totally normal parallel switch like on Day 5. But then you used
two identical LEDs; this time they're two totally different LEDs. The green LED consumes a higher voltage than the
red. When you switch on the red LED, the voltage drops so far that the green LED can't light up anymore. And so the
colour changes.
The PTC Fuse
All your tests have a fuse that protects your components if ever a fault occurs. Otherwise, if you ever accidentally cause a
short circuit, a wire or the battery could become hot or break, or in the worst case, the battery could even explode.
Many fuses simply burn through if someone forms a short circuit. Then you have to get a new one. But your special fuse is
different. This is a self-resetting fuse, also called a PTC fuse. If too much current flows in the case of a short, the PTC fuse
grows hot and then allows only a very little amount of current to continue flowing through it because its resistance increases
significantly. If you then turn off the power and fix the error, the fuse cools off and is like new again.
Attention!
Please don't try to push your fuse to its limits. You see, the battery becomes unusable very quickly when there's a short,
and the PTC fuse heats up to about 60 degrees, hot enough that you can easily burn your fingers on it. The fuse is there
only for emergencies, kind of like the emergency brake on a train.
11
Green-Yellow Switcher
The eleventh door hides a yellow LED. You can use it just like the other colours. A particularly interesting question
is how the yellow LED behaves together with the green LED. Therefore, install the new LED in yesterday's layout
instead of the red LED. And it works: Now you have a green-yellow switcher.
12
Adjustable Brightness
Open Door Number 12 and take out a very special component with three connections. It's an adjustable resistor, a
potentiometer. Components like this are also used as volume controls in radios. Here you should be able to adjust
the brightness of a green LED with it.
The more you turn the dial to the right, the brighter the LED becomes. The potentiometer can be set to resistances
between 0 kΩ and 10 kΩ. But because a series resistor of zero ohms is not allowed and could overload the LED,
we still connect a 0.47 kΩ resistor in series. The total resistance can thus be adjusted between 0.47 kΩ and 10.47
kΩ.
13
Red-Green-White
Behind Door Number 13, you'll find another cable. Now you can also connect the third connection of the potentiometer. You can thereby adjust the electrical voltage in your circuit. At the wiper, that is, at the centre contact of the
potentiometer, a total of three LEDs are connected. The red and the green LED have their own series resistors.
The white LED is indeed connected directly, but at full brightness the 470 Ω resistor has effect.
The opened potentiometer
Turn the knob all the way to the left. All LEDs are off. Then turn it very slowly to the right. First the red LED turns
on, then the green, and lastly the white. Now it's clear: The red LED uses the least voltage, the white LED the most.
Prismatic Colours
Take a CD and use it like a mirror to look at the three LEDs. Then change the angle until you see the white LED as stripes
in all colours of the rainbow. The light spectrum is spread out because the CD has very narrow lines at which the light
waves are reflected. The red and the green LED are also spread out a bit, but they contain only a small portion of the light
spectrum.
The white LED is actually a blue LED. But there's a luminescent material over the LED crystal that the blue light stimulates
to emit all the other colours as well. When the LED is switched off, you can see the yellowish luminescent material on the
inside.
14
Adjustment from Green to Red
A 3.3 kΩ resistor (orange, orange, red) is hiding behind Door Number 14. Today you should make an LED lamp
with adjustable colours. It lights up red, green or in both colours. You can adjust the brightness of both LEDs with
the potentiometer. When the green LED gets brighter when you turn the dial to the left, the red one gets weaker.
And when you turn the potentiometer more to the right, the red LED gets brighter and the green weaker.
Light a piece of paper with the LEDs and line up the LEDs such that they create a single spot of light. Red and
green light together give the colour yellow. So now you can adjust all colours and all shades in the range red –
yellow – green.
15
Automatic Flashing Light
Door Number 15 hides a very special LED. This is a red flashing LED. If you connect it like a normal LED with a
series resistor, it switches on and off constantly all by itself. The red LED with adjustable brightness should stand
alongside it only for comparison.
16
Blinker, Red and Green
Another 470 Ω resistor (yellow, violet, brown) appears behind Door Number 16. Today the blinker should be expanded. Two LEDs should flash at the same time. The green LED is thus connected in series to the red flashing
LED. In addition, there's a white LED, the brightness of which can be adjusted with the potentiometer.
Now both LEDs flash in the same rhythm. If you look more closely, though, you'll see that the green LED never
completely goes out. Thus, some current still flows through the flashing LED even when it is off. In other words, the
controller in the flashing LED continues running and measures the time until it is switched on again.
The Flashing LED
The flashing LED contains an electronic switch that consists of a transistor. But that's not enough; it still takes many more
transistors and other components that together form a complex circuit and have the task of controlling the precise timing.
Everything is put together on a very small piece of silicon that's installed next to the LED crystal.
17
The Alternating Flasher
A pink LED is hiding behind Door Number 17. You should try it out right now with adjustable brightness. At the
same time, another experiment is carried out on the breadboard. Build a red-green alternating flasher. For this purpose, the red flashing LED and the green LED are connected in parallel.
You've already tested the way the alternating flasher works on Day 10. But then a push-button switch was used to
switch a red LED on. This time it's an automatic switch that's built into the flashing LED, the LED controller. And
since the green LED needs more voltage than the red LED, it lights up only during the flashing pauses.
Switch the green and the pink LEDs once. Now the pink LED flashes, and the green lights up steadily with adjustable brightness. This proves it: A pink LED also needs more voltage than a red LED.
Construction of the Pink LED
The pink LED is made similarly to the white LED. The actual LED crystal radiates blue light. But it's coated with a luminescent material that absorbs part of the blue light and emits it again as red light. So the result is that the pink LED actually
has two colours: red and blue. Looking at it using a CD reveals it ...
18
Alternating Flasher with Four LEDs
A 6.8 kΩ resistor appears behind Door Number 18. Today you should make an alternating flasher with four colours.
A yellow LED is placed in series to the flashing LED and therefore flashes in the same rhythm. Parallel to it is yet
another series circuit made up of a green and a pink LED. These two LEDs require more voltage and always light
up when red and yellow are off.
Simplified circuit diagram
The Experimentation Board
On the back of the breadboard, you'll find a thick, soft adhesive film. You can take off the protective film and glue the breadboard to a surface. But you have to think it over carefully before doing so, because the glue strip isn't easy to remove again
after it's been stuck down.
At the same time, the adhesive film is the bottom cover of the breadboard and should never be removed entirely. But here
you see what it looks like underneath, how the springs are placed and how they are formed.
19
Alarm System with Flashing Indicator
Door Number 19 hides an especially large resistor with 22 kΩ (red, red, orange). With it you can build an alarm
system. The green LED lights up, but not the red, because the cable short-circuits it. Green means: Everything's in
order. Connect a string to the cable and tie it to the door. When someone enters the room, that pulls out the cable.
Then the red and the green LED flash. Gotcha!
An especially large resistor with 22 kΩ was used for this alarm system. There's an important reason for that. An
alarm system has to run for a long time. So it's important that only a little current flows. Here it's about 0.3 mA. A
new battery with 2000 mAh could power the system for about 6000 hours. That's more than nine months. Real
alarm systems are mostly connected to the mains. But when they're meant to protect very important items in a museum, people still use a battery as well in case of a power outage.
20
A Game of Skill
Behind Door Number 20, you'll find another resistor. It has 15 kΩ (brown, green, orange) and thus allows only a
very little current flow through. This is important because in the following game, you have to watch the LEDs
closely, but you shouldn't be blinded by them.
When you push the button, the green LED stays off. When you release the button, the green LED flashes in time
with the red flashing LED. Now you should push and hold the button and release it briefly only when the flashing
LED is off. If you miss the interval, the green LED flashes. Everything depends on your quick reaction! How often
can you operate the switch without the LED ever coming on? Have a contest with your friends.
Bridge Circuit
A bridge circuit consists of two series circuits and a component between both. On the left side, the series circuit contains a
resistor and the flashing LED. On the right side are a resistor and a switch. An LED lies between the two and forms the
bridge. The deciding question is now: Is the voltage higher on the left side or on the right side? The green LED can light up
only when the flashing LED is switched on to the left and the switch to the right is off. That is to say, only then is the voltage on the right greater than on the left, so that current can flow through the green LED.
21
The Automatic Colour-Changing LED
Door Number 21 reveals a very special LED. It is an automatic colour-changing LED with the three colours red,
green and blue. Look at this LED very carefully before installing it. Because it has a clear housing, you can use the
front curve like a magnifier and observe everything in strong magnification. Then you can see the silicon chip with
complicated details and the tiny thin wires connected to it. They lead to three LED crystals. The colour-changing
LED thus contains three LEDs of the same type as well as a controller that switches them on and off in quick succession.
The colour-changing LED is operated with adjustable brightness already in the first test. At the same time, you can
carry out another test. The potentiometer is connected here as a voltage distributor so that you can adjust even
small voltages from zero volts. Turn the knob very slowly to the right and thereby increase the voltage. At first, only
the red LED will flash. Then the green joins in. And only at even higher voltage does the blue LED also light up. In
this way, you've examined the voltage series of the LED colours.
Attention!
Never look directly into the LED when it is switched on. Especially the blue light can damage your retina. Because your
eye is less sensitive to blue light, the blue LED looks less bright, but it's still especially dangerous for the eyes.
Pulse Width Modulation
If you look carefully, you can see that the individual LEDs don't just turn on and off but also appear brighter or dimmer.
Sometimes the brightness increases evenly. You might think that a type of automatic potentiometer is built in to change the
amperage. But it works very differently. If you move the entire layout back and forth quickly, you can see light lines of different lengths. The LEDs are actually switched on and off in quick pulses. The length of the pulse is changed, and with it
the average length of time the LED is switched on. This change (modulation) of the pulse length creates the impression of
a brightness change. You can imagine that the LED controller has to be a very complicated circuit if it not only switches the
three LEDs but also uses the pulse width modulation.
22
Flickering White Light
You'll find a 1 kΩ resistor (brown, black, red) behind Door Number 22. Today the colour-changing LED should
cause a white LED to flash in time with it. The colour-changing LED should modulate (change) the current through
the white LED. For this purpose, it needs to be connected in series. The brightness of the white LED will also
change now, sometimes in steps and sometimes seeming to increase steadily. For comparison, two other LEDs
are likewise connected in series but light up with a constant brightness level.
23
Flickering Green Light
Another 1.5 kΩ resistor (brown, green, red) is behind Door Number 23. Today, the green LED should flash in the
opposite rhythm to the colour-changing LED. For this purpose, it needs to be connected in parallel. Every time the
colour-changing controller switches on the red LED, the green LED turns off. An interesting flickering of the green
LED thus results. And even at the green LED, you'll sometimes see steady changes to the brightness.
Additional Test
You now have many different resistors between 470 Ω and 22  kΩ. Have you already learned to read the coloured rings in
the meantime? Sort all your resistors according to their size. And all of them can be tried out in this circuit. In this way, you
can adjust very different brightnesses. Decide for yourself whether you'd like to have more brightness (smaller resistor) or
a longer battery life (bigger resistor).
24
Flickering and Flashing with Six LEDs
Behind the last door you'll find another 1 kΩ resistor (brown, black, red). With two identical 1 kΩ resistors and a
total of six LEDs, you can now build a brightly coloured lamp in which all the LEDs flash or flicker. You actually
have only two LEDs with a built-in controller. But by now you already know all the circuitry tricks with which additional LEDs can also flash or flicker.
Your circuit consists of two LED series circuits and a bridge circuit with two LEDs with opposite polarities. Pay close
attention to the installation direction of each LED. If something doesn't work, it could be because an LED has been
installed the wrong way round.
Now a total of six LEDs are installed, but two white LEDs still have nothing to do. Consider, for yourself how you
could also put them into the circuit. There are very different options for that. First look at the other tests; you're sure
to get an idea from those. You can still use the other resistors, too. All told, you now have so many components
that you can discover completely different circuits. Nothing ventured, nothing gained!