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### Author Topic: 555 timer  (Read 13159 times)

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#### Lazlo

• Guest
##### 555 timer
« on: September 01, 2008, 01:11:46 AM »
I want to design an oscillator that will operate from 20hz to 20KHz. I try with 555 but it seems that with one potentiometer the range 20hz-20Khz is not possible. How else can i make it? Any idea?

#### kammenos

• Guest
##### Re: 555 timer
« Reply #1 on: September 01, 2008, 16:02:17 PM »

#### Lazlo

• Guest
##### Re: 555 timer
« Reply #2 on: September 08, 2008, 18:18:58 PM »
These calculation may help you:
555 Astable calculator

555 Monostable calculator

I tried to use them but i cannot find correct values
If i use for example 16 micro farads for 20Hz, then it is not possible for 20KHz.
Is it possible? Do i use the calculators wrong?

#### Supernova

• Full Member
• Posts: 149
##### Re: 555 timer
« Reply #3 on: September 08, 2008, 22:44:43 PM »
These calculation may help you:
555 Astable calculator

555 Monostable calculator

I tried to use them but i cannot find correct values
If i use for example 16 micro farads for 20Hz, then it is not possible for 20KHz.
Is it possible? Do i use the calculators wrong?

Did you try different capacitors?

#### Lazlo

• Guest
##### Re: 555 timer
« Reply #4 on: September 10, 2008, 08:10:28 AM »
These calculation may help you:
555 Astable calculator

555 Monostable calculator

I tried to use them but i cannot find correct values
If i use for example 16 micro farads for 20Hz, then it is not possible for 20KHz.
Is it possible? Do i use the calculators wrong?

Yes i did but the problem was the same.  I could have small or bug oscillation. Not both with each capacitor.

Did you try different capacitors?

#### Supernova

• Full Member
• Posts: 149
##### Re: 555 timer
« Reply #5 on: September 10, 2008, 13:53:15 PM »
lazlo what exactly did you want to say with your post?

#### kam

• Administrator
• Hero Member
• Posts: 1849
##### Re: 555 timer
« Reply #6 on: September 14, 2008, 16:47:33 PM »
I think nothing. Lazlo should i erase your post for you?

#### Lazlo

• Guest
##### Re: 555 timer
« Reply #7 on: September 17, 2008, 18:36:41 PM »
I put my post in the quote

I wanted to say :
Yes i did but the problem was the same.  I could have small or bug oscillation. Not both with each capacitor.

#### kam

• Administrator
• Hero Member
• Posts: 1849
##### Re: 555 timer
« Reply #8 on: September 18, 2008, 22:12:27 PM »
Of course you have to use different capacitors for reach such a range with one resistor potentionemeter. You may use 3-4 different capacitors and select them with a rotary switch

#### Supernova

• Full Member
• Posts: 149
##### Re: 555 timer
« Reply #9 on: September 20, 2008, 20:49:13 PM »
And also, it will be extremely difficult to adjust a frequency with just a potentiometer from 20Hz to 20Khz. Imagine that you will scroll through all these frequencies with a rotation of 150 degrees of the potentiometer. Unpractical absolutely.

#### Lazlo

• Guest
##### Re: 555 timer
« Reply #10 on: October 05, 2008, 13:43:19 PM »
Ok i get the point. Can someone help me to choose the range capacitors and the number of them?

#### kam

• Administrator
• Hero Member
• Posts: 1849
##### Re: 555 timer
« Reply #11 on: October 07, 2008, 01:03:55 AM »
What is the desired step?

#### Mercury

• Guest
##### Re: 555 timer
« Reply #12 on: October 07, 2008, 23:22:37 PM »
Or how many divisions would you like ti have for this range?

#### Lazlo

• Guest
##### Re: 555 timer
« Reply #13 on: October 15, 2008, 17:27:51 PM »
look, I want 20Hz to 20KHz. That is the acoustic range actually. So it would be nice a step of tens of hertzes. Like

1. 20 - 200 Hz
2. 200 - 2kHz
3. 2KHz - 20Hz

Or if you have another suggestion...

#### kam

• Administrator
• Hero Member
• Posts: 1849
##### Re: 555 timer
« Reply #14 on: October 16, 2008, 16:40:58 PM »
look, I want 20Hz to 20KHz. That is the acoustic range actually. So it would be nice a step of tens of hertzes. Like

1. 20 - 200 Hz
2. 200 - 2kHz
3. 2KHz - 20Hz

Or if you have another suggestion...

Not very good range selection because:
1. from 20 to 200 Hz you have 180 Hz
2. From 200 to 2000 you have 1800 Hz
3. From 2000 to 20000 you have 18000 Hz...

I should suggest a division like:

1. 0 to 5K
2. 5K to 10K
3. 10K to 15K
4. 15K to 20KHz...

or similar. Equal steps