# 555 Timer example

Discussion in 'Homework Help' started by King7, May 14, 2016.

1. ### King7 Thread Starter Member

May 14, 2016
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0
Hey guys how are you?
i'm kind of new at this so can anyone please solve this homework for me
and because that R1 is unknown it is the only homework requirement

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2. ### jpanhalt AAC Fanatic!

Jan 18, 2008
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What is the actual question? Are you given the target frequency? If not, are you asked to solve R1 as a function of the frequency or the other way around?
Have you attempted the problem?

John

3. ### King7 Thread Starter Member

May 14, 2016
31
0
ahhh sorry
the frequency is 50

4. ### jpanhalt AAC Fanatic!

Jan 18, 2008
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ahh sorry
Are you interested in getting help to solve the problem?

John

thumb2 likes this.

May 14, 2016
31
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yup brother

6. ### bertus Administrator

Apr 5, 2008
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Hello,

The frequency is 50 what? Hz,kHz?

Bertus

King7 likes this.

May 14, 2016
31
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Hi bertus
it's 50 Hz

8. ### jpanhalt AAC Fanatic!

Jan 18, 2008
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Some hints. No one here is supposed to solve it for you.
1) Calculate Tl + Th in seconds (or milliseconds)
2) Then calculate Th with the information given
3) Then calculate R1 from its equation and the known values

John

9. ### bertus Administrator

Apr 5, 2008
15,648
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Hello,

Your picture has clear formulas:

Use the directions of John to calculate the cycle time and the high and low times.
Then you can calculate R1.

Bertus

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10. ### King7 Thread Starter Member

May 14, 2016
31
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which capacity i shall use
c1 or c2 ?
or both

Sep 17, 2013
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1,105
Just C1.

12. ### King7 Thread Starter Member

May 14, 2016
31
0
why not c2 it's less

13. ### King7 Thread Starter Member

May 14, 2016
31
0
Hey bertus man
which capacity i shall use
c1 or c2 ?
or both

14. ### bertus Administrator

Apr 5, 2008
15,648
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Hello,

C1 is the timing capacitor,
C2 is for decoupling.

Bertus

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15. ### King7 Thread Starter Member

May 14, 2016
31
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so it's C1 then just like alec said
thanks bro

16. ### bertus Administrator

Apr 5, 2008
15,648
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Hello,

What is the total period time, when the given frequency is 50Hz?

Bertus

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17. ### King7 Thread Starter Member

May 14, 2016
31
0
i got the result (0.160 s) so it will be (160 ms)

18. ### jpanhalt AAC Fanatic!

Jan 18, 2008
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That is not correct.

John

19. ### King7 Thread Starter Member

May 14, 2016
31
0
This is my calculation

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20. ### jpanhalt AAC Fanatic!

Jan 18, 2008
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That also is not correct.
1) Where are your units?
2) Given a frequency of 50 Hz, what is the period? That is all the information your need to calculate it.

Just look at the units. What are the units of frequency? What are the units of period?

John