Triangle wave (170Hz) generator's circuit requirement

[nomi114]

Dear All,

Hope you all are fine. Here i would like to ask onequestion, from last 4 days i am working and thinking for triangle wave generator (holding output frequency of 170 or 180 Hz) by using the crystal oscillator (Frequency = 32.768 Khz). But i am unable to draw and also didn't find such circuit. By using 74HC40103 and 74HC74 i tried to draw and get some suitable results as per requirement, but failed (for simulation purpose i am using LTspice software). If someone can help me in this regard then i shall be highly grateful to you in this act of kindness.

Anxiously waiting for your kind and positive response.

Regards
nomi

 

[wkrug]

The triangle generators I know work with an Operation Amplifier.
There is an Capacitator between the output and the - input of such device - use google to find a schematic.
Square / Triangle Generator
I guess with digital components it is hard to generate a proper triangle signals.

Another possible solution ist an DDS Chip ( with phaseakku output ) , but that need's a microcontroller for working

 

[nomi114]

The triangle generators I know work with an Operation Amplifier.
There is an Capacitator between the output and the - input of such device - use google to find a schematic.
Square / Triangle Generator
I guess with digital components it is hard to generate a proper triangle signals.

Another possible solution ist an DDS Chip ( with phaseakku output ) , but that need's a microcontroller for working

Dear wkrug,

Thanks for your concern and kind reply, you are alright, that triangle wave form can be generated by op Amp.. i already used LF 353 for this purpose... but my confusion is i must wanna use the crystal oscillator (Frequency = 32.768 Khz) and fed signal at the input of LF 353 opamp .. so could not find the such circuit...

so please suggest me how can i design a triangle wave generator (holding output frequency of 170 or 180 Hz) by using the crystal oscillator (Frequency = 32.768 Khz).

Regards

 

[rjenkinsgb]

You can get 170.666Hz by dividing by 32 then 6.

You could use a CD4060 as both oscillator and the first part of the divider (/32) , then a couple of 4013 dual D latches to create a divide by 6.

This is a divide by 3 section:

You need the AND gate at the left but not the right-hand gate, just take the output from Q or /Q on the right hand D type.
Set and reset can be grounded (if using sections of 4013).

The follow that with a divide by 2 (a 4013 section with /Q connected back to D - eg.

That will give a symmetrical square wave. Feed that through a resistor divider to the input of your op amp integrator and adjust the values so you get sawtooth of the appropriate amplitude.

 

[nomi114]

You can get 170.666Hz by dividing by 32 then 6.

You could use a CD4060 as both oscillator and the first part of the divider (/32) , then a couple of 4013 dual D latches to create a divide by 6.

This is a divide by 3 section:

You need the AND gate at the left but not the right-hand gate, just take the output from Q or /Q on the right hand D type.
Set and reset can be grounded (if using sections of 4013).

The follow that with a divide by 2 (a 4013 section with /Q connected back to D - eg.

That will give a symmetrical square wave. Feed that through a resistor divider to the input of your op amp integrator and adjust the values so you get sawtooth of the appropriate amplitude.

Dear rjenkinsgb,

Thank you very much for your kind concern and interest. its good concept, i will do this if i face some problem then i will touch you again, but still one confusion is there in circuit. What should be value of clock and reset in the first circuit and this IC is for (4013 0r CD2060). because i have the model of CD4060 that consist of 14 pins as shown in attached fig. Can i use 74HC74 inplace of 4013 ? please suggest me further.\

Anxiously waiting for your prompt reply.\

Reagrsd

 

[wkrug]

I would take an CD4060 and use a crystal that had a frequency 170 * POWER of 2.
So You can use a Output of 4060 direct to feed the OP.
The time Constant of the OP has to fit with 170Hz You want to have.

 

[Pommie]

Some posters are talking triangle and some sawtooth. The top post says triangle. Is this correct?

Mike.

 

[wkrug]

Some posters are talking triangle and some sawtooth. The top post says triangle. Is this correct?

In the top post would be spoken about triangle.
But with the described digital components of first post only sawtooth is possible IMHO.

...use the crystal oscillator (Frequency = 32.768 Khz) and fed signal at the input of LF 353 opamp

The core of the triange op generator is an integrator. The integration time must fit to the frequency You wanna use.
The problem is to find a divider that can divide 32.768 kHz to 170 or 180 Hz because both division will give You a rest.
And the division factor is not a power of 2 ( e.g. 2, 4, 8, 16, 32, 64, 128, 256, ... ).

So there are only a few solutions possible.
You can use a Digital oscillator with divider and divide additional with CD4017 counter that can divide /2 up to /10.
To calculate witch dividing factors are needed You can try Yourself.
The integrator ( OP ) has to been feed with an symetrical square wave.
The 4017 can't deliver that.
So there has to be a D Flip Flop behind this that divides /2.
Exact 170 or 180 Hz is not possible this way!

Another possible Way is to divide and multiply the Frequency with an PLL circuit e.g. 4046 with the known problems of jitter and locking time.
E.g. divide by 8192 = 4Hz. Multiply by 45 = 180Hz.

I would try to find a crystal with an frequency that has an even dividing factor with 170 or 180Hz best with a power of 2 dividing factor and all would be easy.

 

[Pommie]

But with the described digital components of first post only sawtooth is possible IMHO.

Maybe that is why the OP is not getting a triangle wave.

Mike.

 

[nomi114]

I would take an CD4060 and use a crystal that had a frequency 170 * POWER of 2.
So You can use a Output of 4060 direct to feed the OP.
The time Constant of the OP has to fit with 170Hz You want to have.

dear wkrug,

Thank you very again, but here i am little confused about the connection of crystal oscillator and CD4060, how i can connect with each other, which pins remain NC and pins will useful in case of 14 pins package. I observed that your are expert for this field, frankly speaking i am not very good in this area, because i am new in this field. so if you draw a ckt for right connection on paper and send us . Then i shall be higly grateful to you for this act kindness. (The Pin configuration is attached in previous post)

Anxiously waiting for your positive reply.

Regards
nomi

 

[nomi114]

Some posters are talking triangle and some sawtooth. The top post says triangle. Is this correct?

Mike.

Dear Pommie,

At the output i need Triangle waveform (holding frequency 170Hz) using LF353 (Opamp) we can convert Square/Sawtooth into triangle (hope fully). but how can generate frequency by using crystal Oscillator (wkrug have good idea) , please if you can do in this regard, then please help me. I shall be highly grateful to you for this act of kindness please.

Regards
nomi

 

[alec_t]

output frequency of 170 or 180 Hz

Must it be exactly one of those values, or are you specifying the lower and upper values of an acceptable range?

 

[nomi114]

Must it be exactly one of those values, or are you specifying the lower and upper values of an acceptable range?

Dear alec_t,

First of all thank you very much for your interest, secondly dear not too much variation acceptable, but 160 Hz ~ 180Hz , its acceptable.

Regards

 

[wkrug]

Ok let's try.
The 4060 oscillator runs with the 32768Hz Crystal.
The Output 2^5 ( / 32 ) should be connected to the Clock in of 4017.
4017 output 3 ( 4th Output should be connected to reset of 4017 ).
So that cicuit divides by 3.
At any output 0 up to 2 connect a D-Flip Flop that divides by 2 again and make the signal symetrical.

32768 / 32 = 1024Hz ( 4060 )
1024 / 3 = 341,33Hz ( 4017 )
341,33 / 2 = 170,66Hz ( D-FF )

With the 170 Hz feed the integrator.

The integration Time of the OP must be calculated for a lower frequency, to avoid clipping effects.
To low values will give You a low Amplitude of triangle.
To give here absolute values is difficult, because that depends of saturation voltage of the OP, Voltage heigth and the heigth of the integration voltage.
Simulation and trying will help.

 

[nomi114]

Ok let's try.
The 4060 oscillator runs with the 32768Hz Crystal.
The Output 2^5 ( / 32 ) should be connected to the Clock in of 4017.
4017 output 3 ( 4th Output should be connected to reset of 4017 ).
So that cicuit divides by 3.
At any output 0 up to 2 connect a D-Flip Flop that divides by 2 again and make the signal symetrical.

32768 / 32 = 1024Hz ( 4060 )
1024 / 3 = 341,33Hz ( 4017 )
341,33 / 2 = 170,66Hz ( D-FF )

With the 170 Hz feed the integrator.

The integration Time of the OP must be calculated for a lower frequency, to avoid clipping effects.
To low values will give You a low Amplitude of triangle.
To give here absolute values is difficult, because that depends of saturation voltage of the OP, Voltage heigth and the heigth of the integration voltage.
Simulation and trying will help.

Dear wkrug,

Thank you very much for your reply, here i am confused only for connection strategy for 4060 and crystal oscillator. because i am confused which two pins are used for connections of crystal oscillator, and VCC ??? please help me dear wkrug ( i am using LTspice XVII) .... my model is attached below!!

 

[atferrari]

Dear wkrug,

Thank you very much for your reply, here i am confused only for connection strategy for 4060 and crystal oscillator. because i am confused which two pins are used for connections of crystal oscillator, and VCC ??? please help me dear wkrug ( i am using LTspice XVII) .... my model is attached below!!

View attachment 123194

There was a datasheet giving a circuit.

 

[rjenkinsgb]

This diagram shows how to set up a 32.768 Hz crystal oscillator with a 4060; it uses different outputs, but the osc part is fine:

**broken link removed**

And yes, you can use some 74HC74 ICs in place of 4013s.

Re. some other comments, I was interpreting the waveform requirements as symmetrical ramp-up and ramp-down, as that seemed the most likely output from a single opamp oscillator.

Is that correct, or do you need an asymmetric waveform - slow rise & fast fall or vice-versa?

 

[wkrug]

And yes, you can use some 74HC74 ICs in place of 4013

But only when using 5V Supply.
At higher supply voltages only C-Mos 40.. series will fit.

Higher Voltage increases the output voltage of the triangle signal - when that is needed.
And most Op Amp's can work with higher voltages.

 

[AnalogKid]

That will give a symmetrical square wave. Feed that through a resistor divider to the input of your op amp integrator and adjust the values so you get sawtooth of the appropriate amplitude.

The square wave is not perfectly symmetrical, the opamp output impedance is not perfectly symmetrical, and the opamp input has an offset voltage. These combine to very slowly accumulate a DC charge on the integrator capacitor, and the opamp output eventually will saturate.

ak

 

[nomi114]

Dear all,

Thank you very much for your help and kind cooperation. Actually i am new in this area as well new for using LTspice software. I am unable to generate frequency of 32.786KHz ... i used crystal oscillator can generate the frequency of 24 MHz .. so how can i generate exactly the desired frequency ? For your reference circuit sis attached, Please suggest me which parameter is required to change to get desired freq ???