Flashing Eye Robot / Teaching Electronic Circuits

Flashing Eye RobotMultivibrator circuitClubjesmiddag 18 Mar 2014

Adam Dorrell

Adam Dorrell / Clubjesdag 18 Mar 2014

What this is

• Produce a “Flashing Eye Robot”• Learning basic electronic circuit• Agenda

– Build and understand basic LED circuit with switch

– Make a flashing light circuit with 2 LEDs and 2 transistors

• Technical name: “astable multivibrator”

– Understand how it works• Advanced

– Change some components to change flashing rate

– Two LEDs 1:1 duty cycle also 1 LED like lighthouse 1:10 duty cycle

– Make a lighthouse


Our first circuitElectricity

BatteryResistor

Push button switch


Battery

• A source of electricity• We will use a 9v (9 volt) battery• Electricity flows from + to -• DO NOT LET THE WIRES TOUCH!

– This will cause a short circuit.– May cause a fire, will certainly

flatten battery!


LED

• LED is a “Light Emitting Diode”• Invented in 1962• Light is produced directly from electricity• Can only work one way round

– Long lead goes to +• Needs a resistor (or it burns out)


Resistor

• Resistor reduces voltage level

• It “squeezes” the electricity, letting only some of it through

• They are measured in “Ohms”

• Symbol: Ω or R

• Today we will use 2 types:– Orange-Orange-Brown-

Silver = 330R = 330Ω– Brown-Blk-Yellow-Silver =

100K = 100,000Ω


Push button

• Makes a contact when pushed• Completes our circuit and allows

electricity to flow through it


Learning about the breadboard

Row 1

All holes in the selected column are internally connected.

Row 10 etc


Circuit Layout – Simple LED

330Ω

Breadboard

LED D1R1 – 330R

Button

+9v -9v

Battery


Our first circuit – on the breadboard

What happens when you push button?What happens if you have the LED in the wrong way?


LED Circuit


Press the button


2. Flashing Light Circuit

• We can make a simple circuit to flash LEDs

• It uses 2 transistors as switches

• Also capacitors to store the electrical charge, for the length of flash

• This is the basic part of any computer


Circuit Diagram - Flashing LEDs

Battery

Transistor

Capacitor

Correct name: Astable Multivibrator


Transistor

• Invented in 1947• A transistor is a “Switch”• It is in every item of electronics• In an iphone or computer, there are

1,000,000s in a tiny “chip”• Today we will use a BC547

– It costs EUR 0.10

B = BaseC = CollectorE = Emitter

BC547 NPN bipolar transistor


Capacitor

• A capacitor stores electricity– It holds an electrical

“charge” for some time– We use it to make the

switch stay on for about 1 second


Building it 1

Put in the 1st transistor Make sure it is in the right way!

C – B - E


2

Put in the 1st LED. Make sure it is in the right wayLong lead goes in row 1

Row 1


3

Add the power leadsRed goes in Row 1Black connects to the transistor (E – Emitter)DO NOT CONNECT THE BATTERY YET!

Row 1 (+)

Emitter of transistor (-)


4

Put in the 1st resistorThis is the 330R resistor (orange, orange, brown)Row 2 to the transistor (Collector C)You can bend it into shape


5

Add the small yellow wire to Row 1This connects the (+) up the two halves of the circuit


6

Now add the 2nd resistor. This is the 100K resistor Brown-Blk-Yellow-Silver = 100K = 100,000ΩIt connects from row 1 to the centre of the transistor (Base = B)


7

Add the black wire to the transistor E connection (-)This will supply the (-) power to the other half of the circuit


8

Add the 1st capacitor.This connects to the C Collector of transistor 1 and the B Base of transistor 2

Add the 2nd capacitor.This connects to the B base (centre) of transistor 1 and the C Collector of transistor 2 BE CAREFUL NOT TO LET THE WIRES TOUCH!

Don’t let the wires cross ⊖

⊖


9

Connect the yellow wireAdd resistor 4This is the 330R This is the 330R resistor (orange, orange, brown)Row 2 to the transistor 2 (Collector C)

Now add the 3nd resistor. This is the 100K resistor Brown-Blk-Yellow-Silver = 100K = 100,000ΩIt connects from row 1 to the centre of the transistor 2 (Base = B)


10

Bend the resistor into shapeDon’t let the wires touch


11

Connect the black wire

Add transistor 2Take care to put in the right way!

⊖

⊖


12

Add LED 2Careful to put in the right way!The long lead goes into row 1


13

Now you can connect to the battery!Let’s check it works!


Circuit Layout – Flashing Lights

+9v -9v

LED D1

LED D2

Q1 BC547

R1 – 330R

Q2 BC547

R2 – 330R

R4 – 100K

C2 10u ⊖R4 – 100K

C1 10u

⊖

Battery


Making the Robot


How it works

Battery

Transistor

Capacitor


How it works 2

Battery

Transistor

Capacitor


Advanced (if time)

• Change colour of LEDs• Add more LEDs• Change the values of the resistor and capacitor• Make the flash 1:10 instead of 1:1


Parts list• PARTS LIST

– 2 x BC548 NPN transistor – 2 x LED 10mm mix colour– 2 x 330R resistor (0.5w)– 2 x 10u Capacitor– 2 x 100K Resistor– 1 x 9v battery– 1 x 9v holder– 1 x button 6mm sq– Small breadboard

• PARTS LIST (NL)– 2 x BC548 Bipolaire NPN transistor – 2 x LED 10mm mix kleur– 2 x 330R weerstand (0.5w)– 2 x 10u Elektrolyt condensator – 2 x 100K weerstand – 1 x 9v 9V batterij (blok)– 1 x 9v Batterijclip– 1 x Druktoets 6mm sq– Insteekprintplaat

Flashing Eye Robot / Teaching Electronic Circuits

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