AE655000E

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ELECTRONICS IN DAILY LIFE

Students’ lab manual for 655000 Breadboard electronics set, 6 groups Version 2017-07-13 / HS

© Frederiksen Scientific A/S

Overview of components

Name Number Schematics Breadboard

drawing

Battery 1

Resistor

4 of 1 kΩ

4 of 4,7 kΩ

4 of 10 kΩ

4 of 100 kΩ

LED 4

Transistor 4

Light dependent resistor 1

Capacitor

2 of 10 µF

2 of 100 µF

1 of 1000 µF

Switch 2

Relay 1

Buzzer 1

Potentiometer 1

Temperature sensitive resistor 1

10 cm mini cable

0,8 mm male – male

1 yellow

1 blue

20 cm mini cable

0,8 mm male – male

1 red

1 black

Adapter cable

0,8 mm female – 4 mm female

1 red

1 black

Battery clip 1

Breadboard 1

1 – The Light emitting diode (LED)

How do you make an LED shine weakly, resp. brightly?

a)

Build the circuit so that the current from the battery runs

through an LED (LED1) and a 1 kΩ resistor (R1).

(The short blue lead on the drawing makes it easy to change

the circuit in the next paragraph.)

The longest lead on the LED connects to plus. You will

notice also that the rim at the base of the LED is missing

next to the other leg. On the breadboard drawing both

features are marked.

An LED must always be in a series circuit with a resistor –

otherwise a large current will flow and the diode will be

damaged.

Now, try to exchange the resistor R1 with one of 10 kΩ.

What happens to the light?

Now, try to exchange R1 with a resistor of 100 kΩ.

What happens to the light? (You may need to shade the LED

with your hands or turn off the light.)

Write down your observations!

b)

Change the circuit to let the current go through an ammeter

with a range that lets you measure down to 0.01 A

Start with a 1 kΩ resistor and write down the size of the

current.

Change to a 10 kΩ resistor and write down the size of the

current.

Do the same with a 100 kΩ resistor.

What happens to the current when the resistance

increases?

What is the relationship between the current and the

brightness of the LED?

c)

A diode is also called a rectifier.

Remove the LED and re-insert it backwards (i.e. with

the longest lead away from plus).

How large is the current now?

Is the LED lit?

2 – The transistor

How can you make a tiny current control a much larger one?

– We use the transistor as a switch.

The transistor has three connections called base, emitter

and collector. To the right you can see the schematics

symbol and drawings from below (one) and above (three)

– with the leads bend in the right direction for experiments

with the breadboard.

a)

Build the transistor circuit as shown. Bend the leads of the

transistor as indicated to make it fit. Be careful not to

confuse the leads!

On the ammeter, select a range capable of measuring down

to 0.01 A.

If everything is OK, the LED should light up!

In case it doesn’t, go through the connections carefully:

Both the transistor and the LED must be oriented correctly.

The ammeter must be turned un – and must be set for

measuring DC current.

In this setup, the ammeter measures the current flowing

into the base of the transistor.

How large is the base current? – Write down.

b)

Swap the ammeter and the blue wire in order to change the

circuit as shown.

Now, the ammeter measures the current flowing into the

collector of the transistor.

How large is the collector current? – Write down.

Is the base current or the collector current largest?

How many times larger?

3 – Light sensor

How does a photocell work?

a)

The photocell we use is called an LDR – a Light Dependent

Resistor.

First, we will measure the resistance in the LDR with an

ohmmeter. The easiest is probably to insert the photocell

and the leads to the multimeter into the breadboard.

How large is the resistance with light on the photocell?

Place the photocell in a shadow – e.g. by putting a finger on

top of it. How large is the resistance now?

Describe how an LDR behaves in light and darkness.

b)

Build the circuit as shown.

Remember as always to orient the transistor and the LED

correctly.

When everything is correctly assembled, the LED should

light up – provided the LDR is illuminated.

The circuit is quite sensitive – is has to be rather dark to

turn off the LED. (Use both hands for shading.)

Does it work? Write down your observations!

4 –The capacitor

How can a capacitor be used for creating a delay? We

investigate charging and discharging of a capacitor.

a)

The capacitance value is printed on the capacitor. The

Greek letter ”µ” is usually pronounced “mju”. The unit ”µF”

is read as “micro farad”. It is also OK to write it as “uF”. We

start with 100 µF.

Build the circuit as shown. Take care to turn the capacitor

the right way – otherwise it can be damaged. Minus is

clearly marked. And as usual, the diode must also be

oriented correctly.

When pressing the switch down, current flows – the diode

lights up. What happens when the switch is released?

Try to remove the capacitor from the circuit and compare

the behaviour. What is the difference? – Write down.

The capacitor is charged through the switch and afterwards

discharged through the resistor and the LED.

b)

Try varying the capacitance by changing the capacitor. Test

the functioning of the circuit with all three capacitor sizes.

Write down what happens when using a small (10 µF), an

intermediate (100 µF) and a large (1000 µF) capacitor.

5 – Time delay with capacitor and

transistor

How can we obtain very long delays? What is the

significance of the resistance when discharging a capacitor?

a)

We will use a transistor switch combined with a capacitor.

Build the circuit shown with the small 10 µF capacitor.

When current flows through the switch the capacitor is

charged. It is discharged through the 10 kΩ resistor (R2)

and the base of the transistor.

If everything is connected correct the LED should light up

when the switch is pressed.

What happens when releasing the button? – Write it down.

b)

Change the capacitor to the intermediate one (100 µF).

What do you expect to happen? Did it happen?

c)

Keep the 100 µF capacitor in the circuit but change the

resistor R2 from 10 kΩ to 1 kΩ.

Write down what happened to the delay time.

Change resistor R2 again – this time using a 100 kΩ resistor.

What would you expect? What happened?

Don’t forget to write down.

6 – Staircase lighting

How do you make the lighting of a stairwell stay on some

time after turning it on?

a)

Build the circuit shown.

It starts like that in the previous paragraph but a relay

control has been added.

A relay is an electrically controlled switch. Relays exist with

very high current ratings. The relay we use can, however,

only switch currents up to 1 A. When the LED turns on and

off you can hear the relay giving a faint click.

b)

Now you will use the circuit for controlling a

lamp bulb. You will need a 12 V power supply

and a 12 V / 0.25 A incandescent lamp.

Add this to the circuit as shown and adjust the

power supply to 12 V.

Press the button – is it working?

c)

Try now with another capacitor in order to

obtain a sufficiently long lighting interval. You can also try

to change the resistor that is determining the delay time

(…which one was that?)

Write down the delay times you obtain with the different

combinations of resistor and capacitor.

7 – A temperature sensor

How can the temperature control a current?

a)

We use an NTC – a temperature dependent resistor. (NTC

stands for “Negative Temperature Coefficient”).

Start by examining the NTC resistor with an ohmmeter –

like you did with the LDR in paragraph 3.

How large is the resistance at room temperature?

Try heating the NTC by holding it between two fingers.

What is the resistance at “finger temperature”?

b)

Build the circuit as shown.

P1 is a potentiometer – i.e. a variable resistor. The current

flowing out of the viper lead runs through R3 to the base of

the transistor. P1 is used for placing the sensitive interval of

the circuit near room temperature.

Some connections on the breadboard are a little bit special

this time:

1 - The connection between the C strip and k32 (the k hole

in strip 32) is made from a bit of uninsulated wire – e.g.

what was cut off a component lead. (Shown as a black line.)

2 - The resistor between B and k34 has longer legs than

usual.

3 - The NTC resistor is placed slightly slanted.

As you may have noted, the resistance of the NTC resistor

does not vary as much as that of the LDR. Therefore we use

two transistors in order to make a more sensitive circuit.

Adjust P1 until the LED lights up when you heat the NTC and

turn off again when it cools off.

Write down how everything works!

Try turning P1 completely from one extreme to the other

while keeping an eye at both LEDs. Describe how fast and

how much LED1 and LED2 changes their brightness.

8 – Memory

Can an electronic circuit remember? We build a 1 bit

memory.

a)

Build a transistor switch again. – See the drawings.

Notice the blue wire that connects to either 0 V (the C strip

on the breadboard) or 9 V (the B strip).

As a start, connect the blue wire to 9 V – this should light up

the LED.

You will now use a voltmeter connected

between 0V and one of the nodes called Input

and Output on the image. There is no need for

precise readings, simply decide if the voltage

is high (more than 4 V) or low (below 4 V).

When the input is high: What is the output?

When the output is high: What is the input?

Write your observations down.

b)

The circuit is now extended with another transistor switch.

Connect the output of the first switch with the input of the

next. With a wire, connect output 2 back to input 1 (see

drawing).

In fact, the memory is finished now – but its content will be

random! Now it is time to make it remember what you

decides.

This is done by the circuitry with the two pushbutton

switches, connected by the yellow wire directly to the base

of the first transistor. The complete circuit is drawn below.

Now the circuit remembers which switch you press. Try it!

Write down what happens.

9 – LED flasher

How does a car’s hazard light work?

a)

Try to build the circuit shown.

Insert the two capacitors last – there is just room enough.

If everything has been connected correctly, you have

made an LED flasher!

b)

Which of the components do you think are important for

how fast the LEDs are flashing?

Can you change the circuit to make it flash ten times faster?

Can you make it flash ten times slower?

Remember to write down your modifications and

observations.

10 – Burglar alarm

Vi build a light sensitive burglar alarm!

a)

The circuit consists of a light sensor and a slightly modified

memory. You will also need: Black paper (approx. 5 x 7 cm),

tape, a flashlight or similar.

Build the circuit as shown. – Note the use of 10 kΩ (instead

of 100 kΩ) as base resistors in the memory (R2 and R4), and

that one of the collector resistors in the memory has been

replaced by a buzzer (R1 is missing, compared with the

paragraph “Memory”).

The light sensor connects to the memory through an LED

(LED4) – here used as a rectifier.

Take care to illuminate the LDR when you

connect the battery. In case the buzzer

turns on it should be possible to stop it with

the switch.

b)

Make a tube of black paper:

Roll it around e.g. a thick speed marker and

fix it with tape.

If you places the tube around the LDR and

shades it with your hand, the alarm

should go off.

Even if the photocell is illuminated again,

the alarm must continue to sound until

you press the button.

Bend the photocell leads and place the

tube to make the photocell “peek”

horizontally through the tube. Fix the

tube to the breadboard – see the photo.

When the light from the flashlight falls

onto the sensor, the alarm can be

stopped with the switch – but as soon as

the light beam is broken, it goes off!

11 – Thermostat

How do you control temperature? We build a

thermostat

a)

Build the circuit shown.

The thermostat consists of a temperature sensor and

a relay controller. Refer to paragraph 7 concerning

the connections to the potentiometer.

Check the circuit: When you turn the potentiometer

P1 completely up and down, you should hear the relay click.

Turn completely down to make LED2

light up. Turn slowly up until the relay

clicks (turns on) – together with LED2

turning off. You should now be able

to make the relay click again (turn off)

if you warm the NTC resistor with

your fingers. – And when it cools

down again, the relay should click

once more.

You may need to fine tune P1.

b)

The circuit is used for controlling a light bulb. You will need

a 12 V power supply and a 12 V / 0.25 A incandescent lamp.

(Not an LED bulb – we need the heat from the light bulb.)

Add this to the circuit as shown and adjust the power

supply to 12 V.

The lamp must turn off and on when the NTC is heated and

cooled down.

Place the light bulb so that it touches the NTC.

Preferably without you having to hold it there.

The lamp will blink slowly!

Write an explanation of what happens!