555 to triangular wave

Thread Starter

drakedog2

Joined Sep 24, 2014
18
I have made a triangle wave from 555 square wave. Below are circuit and simulation.

1633192791016.png
1633192820323.png

I want the triangular wave from in the range from 0.4 to 2V. Do I have add opamp to achieve it?
 

Audioguru again

Joined Oct 21, 2019
3,828
Your 555 does not produce a squarewave, it is a rectangular wave because its capacitor charges from two series resistors but discharges from only one resistor. Then the integrated waveform is a sawtooth, not a triangle.

The first opamp (fed from the 555) is useless.

The lousy old 324 opamp has a poor high frequency response that cannot produce the harmonics of a triangle wave. The simulation software might not know it.
 

MrSalts

Joined Apr 2, 2020
712
I have made a triangle wave from 555 square wave. Below are circuit and simulation.

View attachment 249333
View attachment 249334
So far, it doesn't look like you've "made" anything, you've only simulated something. Which simulator are you using. Look at the circle data points in the blue "triangle data". They appear to be making a sine wave. Did your simulator just cram the triangle wave into fit the pattern of data points? Is your 555 signal higher frequency than the iteration steps of simulator? Try bumping up the frequency (shortening the interval) of the simulator's steps.
 

Thread Starter

drakedog2

Joined Sep 24, 2014
18
I try to make the triangular wave that feed modulation input of driver. The voltage range of modulation input is from 0.4 to 2 V.

I have only simulated it and haven't made anything yet.

I have some LM556. Should I replace LM324 with it?

I cannot take out 555 because I need the rectangular wave too.

1633206774245.png
 

Audioguru again

Joined Oct 21, 2019
3,828
Your latest "triangle" leans to the left side because the "squarewave" is not perfectly square.
A CD4047 IC has an RC oscillator driving a divide-by-two so its outputs are a perfect square.
Here is yours:
 

Attachments

AnalogKid

Joined Aug 1, 2013
9,479
The DC level of your output waveform increases until the U15A output begins to clip. This is because there is no feedback from the integrator output to the comparator input.

As in post #5, there is a very common 2-opamp circuit that produces both a square wave and triangle wave. It will do everything you say you want with 2 sections of an LM324. You can then use a third LM324 section to buffer the triangle signal after it has been adjusted for amplitude and output voltage range. Note that the output quality will be low (small non-linearities, crossover distortion, etc.) due to the low performance LM324.

ak
 

Ian0

Joined Aug 7, 2020
3,754
With a bit of manipulation of the pgnd voltage on U2, and R2 and R3 it should be possible to output a 0.4V to 2V triangle that the TS originally wanted. A rail-to-rail output op-amp would make the maths easier!
 

MrSalts

Joined Apr 2, 2020
712
NOTE: this circuit posted immediately above by LowQcab DOES NOT produce a triangle wave. It is simply a wave that charges and discharges a capacitor without constant current control. It looks more like a shark-fin (almost a triangle). If that is good enough for your application, fine. If not, use an appropriate circuit.

A true triangle wave is produced by the circuit posted by @crutschow
 

LowQCab

Joined Nov 6, 2012
1,308
True, it's High-Impedance, and not perfectly symmetrical,
but the "area-under-curve" is precisely the same as a proper "perfect" Triangle-Wave,
so it's well suited to PWM applications.

Its usefulness depends on what is meant by .......
""......make the triangular wave that feed modulation input of driver. ""

It's just an option, and it's a very simply and easy one.
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Audioguru again

Joined Oct 21, 2019
3,828
The fist circuit in post #1 produced 550Hz.
The second circuit in post #6 produced 98Hz.
The third circuit in post #12 produces 2kHz.
Why does the circuit in post #16 produce ultrasonic 32.5kHz?
 

LowQCab

Joined Nov 6, 2012
1,308
The fist circuit in post #1 produced 550Hz.
The second circuit in post #6 produced 98Hz.
The third circuit in post #12 produces 2kHz.
Why does the circuit in post #16 produce ultrasonic 32.5kHz?
If You will expand the Picture You will find the formula for
the Frequency generated by the Circuit on page 16.
The Capacitance is calculated in Farads.

The shown values were from a different project.
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