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555 /556 Timer

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Overview & Introduction

update with RC and cap

update with OpAmp

add duty cycle ratios with 555

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See Appendix A, for Licensing & Attribution information

by-nc-sa-3.0

https://creativecommons.org/licenses/by-nc-sa/3.0/

https://creativecommons.org/faq/#what-does-some-rights-reserved-mean

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Resources & Materials Needed

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What You Will Know…

Prior Knowledge

How…
How…

What You Will Know & Be Able To Do

Calculate…
Build a…
Be able to describe… how an R/C circuit works

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Objectives

“An instructional objective is a written statement of what a learner will be able to do when he/she has completed a learning experience successfully.”
1. Behavior – what the student will do
2. Condition – location, time, materials resources
3. Criteria – how it will be measured

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How Will You Be Measured

To what extent will the verb be measured?
How will success be determined?

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New Words…

Oscillator
Relaxation Oscillator
Duty Cycles
Monostable
Bistable
Astable

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555 Timer Overview

The 555 Timer Oscillator which is more commonly called the “555 Timer” is a dedicated IC’s

Designed to produce an output waveform
It can create square waves, as well as other waveforms
It requires just a few extra external Resistors and Capacitors as timing components

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Why 555?

The 555 timer gets its name from the three 5kΩ resistors it uses to generate the two comparators reference voltage
It is a very cheap, popular and useful precision timing device
It can act as either a simple timer to generate single pulses or long time delays
Bistable, where it can be used as a On/Off switch
Or as a relaxation oscillator producing stabilized waveforms of varying duty cycles from 50 to 100%.

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How A 555 Timer Works

https://www.youtube.com/watch?v=i0SNb__dkYI

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2/3 Vcc

1/3 Vcc

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LAB TIME

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Bistable

Acts like a Flip/Flop
Presenting a “low” on the reset or trigger pins will cause the output to change

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Bistable Timer Lab

Using a breadboard…
Build a Bistable circuit
Show me… and…
Why you might use a circuit like this, rather than just a switch?... It looks like a On/Off switch

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Monostable

Triggers a pulse of variable width
t = 1.1R₁C₁
MonoStable Calculators

Solve for time
Solve with components

100KΩ

10uF

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Monostable Timer Lab

Using a breadboard…
Build a Monostable circuit
Show me… and…
Calculate what the R1 and C1 values are needed for a

1 sec pulse
10 second pulse
1 min pulse

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Monostable Timer Lab

Using a breadboard…
Build a Monostable circuit
Show me… and…
Turn in to IC what the R1 and C1 values are needed for a

1 sec pulse
10 second pulse
1 min pulse

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Astable

Generates a repeating output wave form

t_on = 0.69 * C₁ * (R₁+R₂)
t_off = 0.69 * C₁ * R₂

555 Timer Calculators

470KΩ

1uF

1KΩ

Increase C to increase the period (reduce the frequency).

Increase R1 to increase High Time (T1), without affecting the Low Time (T0).

Increase R2 to increase High Time (T1), increase Low Time (T0) and decrease the duty cycle.

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Astable Timer Lab

Using a breadboard…
Build a Monostable circuit
Show me… and…
Turn in what the R₁ R₂ and C₁ values are needed for a

1 sec Square Wave
0.5 sec Square Wave

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Astable Timer Lab

Using a breadboard…
Build a Monostable circuit
Show me… and…
Turn in what the R₁ R₂ and C₁ values are needed for a

1 sec Square Wave
0.5 sec Square Wave

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Monostable 555 Timer

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Assessment

Assessment Type(s):

Demonstrations
Interviews
Journals
Observations
Labs
Projects
Portfolios
Rubrics
Surveys
Teacher-Made Test
Writing Samples

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Reference Slides

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Learning Domain, CTE Standards and Stuff like that…

Learning Domain

[ ] cognitive [ ] affective[ ] psychomotor

What are some cognitive skills required for success in your pathway?
What are some affective skills required for success in your pathway?
What are some psychomotor skills required for success in your pathway?

Time:

Lecture
Lab

Standards

CTE
CCSS
NCSS

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https://www.youtube.com/watch?time_continue=346&v=EkJ---lnrn8 (go to time 5:30)

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555 vs 556?

556 Timer is a Dual 555
This means there are 2 555 in a 556 Timer

See pins for Timer “A” and Timer “B”

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Lets Build Some Circuits

555 Time in STEAM Clown’s Closet

Flashing LED Circuit

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Appendix

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Appendix A: License & Attribution

This interpretation is primarily the Intellectual Property of Jim Burnham, Top STEAM Clown, at STEAMClown.org
This presentation and content is distributed under the Creative Commons License CC-by-nc-sa-3.0
My best attempt to properly attribute, or reference any other sources or work I have used are listed in Appendix B

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Appendix B: Attribution for Sources Used

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