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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
Adam Dorrell / Clubjesdag 18 Mar 2014
Our first circuitElectricity
BatteryResistor
Push button switch
Adam Dorrell / Clubjesdag 18 Mar 2014
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!
Adam Dorrell / Clubjesdag 18 Mar 2014
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)
Adam Dorrell / Clubjesdag 18 Mar 2014
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
Adam Dorrell / Clubjesdag 18 Mar 2014
Push button
• Makes a contact when pushed• Completes our circuit and allows
electricity to flow through it
Adam Dorrell / Clubjesdag 18 Mar 2014
Learning about the breadboard
Row 1
All holes in the selected column are internally connected.
Row 10 etc
Adam Dorrell / Clubjesdag 18 Mar 2014
Circuit Layout – Simple LED
330Ω
Breadboard
LED D1R1 – 330R
Button
+9v -9v
Battery
Adam Dorrell / Clubjesdag 18 Mar 2014
Our first circuit – on the breadboard
What happens when you push button?What happens if you have the LED in the wrong way?
Adam Dorrell / Clubjesdag 18 Mar 2014
LED Circuit
Adam Dorrell / Clubjesdag 18 Mar 2014
Press the button
Adam Dorrell / Clubjesdag 18 Mar 2014
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
Adam Dorrell / Clubjesdag 18 Mar 2014
Circuit Diagram - Flashing LEDs
Battery
Transistor
Capacitor
Correct name: Astable Multivibrator
Adam Dorrell / Clubjesdag 18 Mar 2014
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
Adam Dorrell / Clubjesdag 18 Mar 2014
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
Adam Dorrell / Clubjesdag 18 Mar 2014
Building it 1
Put in the 1st transistor Make sure it is in the right way!
C – B - E
Adam Dorrell / Clubjesdag 18 Mar 2014
2
Put in the 1st LED. Make sure it is in the right wayLong lead goes in row 1
Row 1
Adam Dorrell / Clubjesdag 18 Mar 2014
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 (-)
Adam Dorrell / Clubjesdag 18 Mar 2014
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
Adam Dorrell / Clubjesdag 18 Mar 2014
5
Add the small yellow wire to Row 1This connects the (+) up the two halves of the circuit
Adam Dorrell / Clubjesdag 18 Mar 2014
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)
Adam Dorrell / Clubjesdag 18 Mar 2014
7
Add the black wire to the transistor E connection (-)This will supply the (-) power to the other half of the circuit
Adam Dorrell / Clubjesdag 18 Mar 2014
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 ⊖
⊖
Adam Dorrell / Clubjesdag 18 Mar 2014
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)
Adam Dorrell / Clubjesdag 18 Mar 2014
10
Bend the resistor into shapeDon’t let the wires touch
Adam Dorrell / Clubjesdag 18 Mar 2014
11
Connect the black wire
Add transistor 2Take care to put in the right way!
⊖
⊖
Adam Dorrell / Clubjesdag 18 Mar 2014
12
Add LED 2Careful to put in the right way!The long lead goes into row 1
Adam Dorrell / Clubjesdag 18 Mar 2014
13
Now you can connect to the battery!Let’s check it works!
Adam Dorrell / Clubjesdag 18 Mar 2014
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
Adam Dorrell / Clubjesdag 18 Mar 2014
Making the Robot
Adam Dorrell / Clubjesdag 18 Mar 2014
Adam Dorrell / Clubjesdag 18 Mar 2014
How it works
Battery
Transistor
Capacitor
Adam Dorrell / Clubjesdag 18 Mar 2014
How it works 2
Battery
Transistor
Capacitor
Adam Dorrell / Clubjesdag 18 Mar 2014
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
Adam Dorrell / Clubjesdag 18 Mar 2014
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