Intro to Electronics Week 3 Intro to Electronics, Week 3 Last - - PowerPoint PPT Presentation

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Intro to Electronics Week 3 Intro to Electronics, Week 3 Last - - PowerPoint PPT Presentation

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Intro to Electronics Week 3 Intro to Electronics, Week 3 Last updated Oct. 24, 2012 1 Thanks to EMSL for the idea: http://www.evilmadscientist.com/article.php/nightlight Make a night light TODAYS P PROJECT Intro to Electronics, Week 3

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SLIDE 1

Intro to Electronics

Week 3

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 1

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SLIDE 2

TODAY’S P PROJECT

Make a night light

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 2 Thanks to EMSL for the idea: http://www.evilmadscientist.com/article.php/nightlight

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SLIDE 3

LED

  • Remember these?
  • What does it take to light one?

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 3

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SLIDE 4

Go ahead and do it

6 V 220

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 4

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SLIDE 5

Go ahead and do it

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 5

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SLIDE 6

Transistor

  • “The fundamental building block of modern

electronic devices” (Wikipedia)

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 6

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SLIDE 7

Why so important?

  • Amplification

– Make a small input change cause a large

  • utput change

– Useful for audio and radio

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 7

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SLIDE 8

Why so important?

  • Switching

– Control whether something else turns on or off – Useful for digital logic and control

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 8

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SLIDE 9

Bipolar junction transistor

  • Common transistor type

– Only one we’ll use in this class – We’ll just use it for switching

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 9

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SLIDE 10

BJT

  • Three terminals

– Base – Emitter – Collector

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 10

Base Emitter Collector

Input Output

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SLIDE 11

BJT

  • Current flows into base
  • Transistor allows

current to flow into collector

  • Both currents come
  • ut the emitter

– Hence the arrow pointing out

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 11

Base Emitter Collector

Input Output

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SLIDE 12

Let’s add one

6 V 220 2N3904 1 k

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 12

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SLIDE 13

Sort of boring, right?

  • No real difference from before

– Switch turns transistor on and off – Transistor turning on and off makes LED do the same

  • Need another way to control the transistor

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 13

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SLIDE 14

Phototransistor

  • Instead of supplying

base current, shine a light on it!

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 14

“Base” Emitter Collector

Input Output

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SLIDE 15

Let’s add one

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 15

6 V 220 2N3904 1 k

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SLIDE 16

Let’s add one

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 16

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What happens?

  • Light shines on the phototransistor
  • Base current no longer goes to BJT

– Goes straight to ground instead

  • BJT turns off è LED turns off

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 17

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SLIDE 18

Why isn’t this working?

  • Phototransistors tend to be sensitive to

just one kind of light

– In this case: Infrared (most common case)

  • Fluorescent lights don’t put out

much infrared

– Try another light (or the sun!)

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 18

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SLIDE 19

Why two transistors?

  • Without them, we’d

have a day light, not a night light

6 V 220

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 19

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SLIDE 20

A thought

  • We just used one transistor to control

another transistor!

– Beginning of digital logic

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 20

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SLIDE 21

Digital logic

  • Combine switches to do exciting things!
  • Basic building blocks: Logic gates

– Can be made entirely of transistors

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 21

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SLIDE 22

Logic gates

  • Take one or more inputs
  • Follow some sort of rules
  • Produce an output

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 22

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SLIDE 23

Examples

  • AND gate: Two inputs

– If they’re both on, the output’s on – Otherwise, the output’s off

  • OR gate: Two inputs

– If either one is on, the output’s on – Otherwise, the output’s off

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 23

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SLIDE 24

Examples

  • NOT gate: One input

– If it’s on, the output’s off – Otherwise, the output’s on

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 24

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SLIDE 25

Back to the night light

– If the input’s on…

  • There’s ambient light

– …the output’s off!

  • The LED stays unlit

– If the input’s off…

  • There’s no ambient light

– …the output’s on!

  • The LED lights up

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 25

  • You just made a NOT gate!
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SLIDE 26

Compare

In Out

6 V 220 2N3904 1 k

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 26 http://www.kpsec.freeuk.com/ trancirc.htm#inverter

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SLIDE 27

Remember this

  • We’ll do more with logic in a couple of weeks

– We’ll use premade gates and such, though

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 27

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SLIDE 28

That’s it for tonight

  • Next week

– Oscillators – Timers

Last updated Oct. 24, 2012 Intro to Electronics, Week 3 28