# simple waveform generator

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#### guskenny83

##### Newbie level 3
waveform generator ic

Hi,

i was just wondering if someone could help me with something im trying to build..

i am looking for a simple circuit diagram for a waveform generator, battery powered, can switch between sine/triangle/square waves and is variable from 1Hz to about 1kHz - or something that is kinda similar that i can change the components to achieve the desired frequencies..

i've found some diagrams for ones that range from 1Hz to 1MHz, but as i want it so i can play around with audio frequencies, the range is too great.. is changing the frequency range as simple as changing the value of the potentiometer to one that ranges from 1k Ohm to 1M Ohm and capacitor to 1uF thus giving a range from 1 ≤ f ≤ 1000 (f=1/RC) or would there be more involved in changing an existing diagram?

ultimately i'd like to make two of these that run at the same time so i can play around with destructive interferences and things, but ill be happy with just making this to start with!

as for my electronics experience, i used to play around with simple kits when i was little and i did a 6 month course in electronics in middle high-school, but aside from soldering techniques and a few things about ohms law and such, i've forgotten most of it..

alright, any help would be greatly appreciated..

thanks
gus

#### doraemon

##### Super Moderator
Staff member
Hello!

There are single chip wave generators (sine, triangle, square, etc...).
Take a look at .

There are schematics, so it is close to the ideal solution to make your own
2 simultaneous waves generator.

Dora

guskenny83 said:
Hi,

i was just wondering if someone could help me with something im trying to build..

i am looking for a simple circuit diagram for a waveform generator, battery powered, can switch between sine/triangle/square waves and is variable from 1Hz to about 1kHz - or something that is kinda similar that i can change the components to achieve the desired frequencies..

i've found some diagrams for ones that range from 1Hz to 1MHz, but as i want it so i can play around with audio frequencies, the range is too great.. is changing the frequency range as simple as changing the value of the potentiometer to one that ranges from 1k Ohm to 1M Ohm and capacitor to 1uF thus giving a range from 1 ≤ f ≤ 1000 (f=1/RC) or would there be more involved in changing an existing diagram?

ultimately i'd like to make two of these that run at the same time so i can play around with destructive interferences and things, but ill be happy with just making this to start with!

as for my electronics experience, i used to play around with simple kits when i was little and i did a 6 month course in electronics in middle high-school, but aside from soldering techniques and a few things about ohms law and such, i've forgotten most of it..

alright, any help would be greatly appreciated..

thanks
gus

#### rituparnasaikia

##### Member level 3
build waveform generator

You can use 555 IC as well as an OP-AMP
The 555 will be the generator and using OP AMP you can change the shape of the wave form.

#### guskenny83

##### Newbie level 3
function generator

i found this circuit on the internet that uses the 741 IC op amp which looks like it might be helpful..

a couple of questions about it though..

can anyone tell me the frequency range of the output? what would i need to change in order to make the range from 1Hz to 1kHz?

second, the power supply for this is 15V, would i need to change anything to make it run off a 9V battery?

thirdly, would it have enough amplitude to play direct to a speaker or would i need to run it through an amp?

and finally, is the last pot -R8- a logarithmic pot because its for amplitude?

thanks heaps for all your help

cheers
gus

#### FvM

##### Super Moderator
Staff member

Three timing resistors have to be changed for a frequency variation, there are much better circuits for a frequency variable generator.

I think, it's not correct to talk of "sine" waveform in case of first order lowpass filtered triangle.

The circuit requires a bipolar (+/- 15V) supply, so two 9V batteries would be needed.

An OP output can't drive a speaker without additional current amplification.

I suggest to use a XR2206 function generator, you can build a function generator with a single frequency setting resistor.

#### doraemon

##### Super Moderator
Staff member
simple waveform

Hello!

Yes, and the 2206 has a kind of guarantee on its signals (the sinewave is really
a sinewave) and the linearity is good as shown in my previous post's link.
This circuit has been around for years and it should be easy to find.

Dora

FvM said:
I suggest to use a XR2206 function generator, you can build a function generator with a single frequency setting resistor.

#### mago

##### Junior Member level 2
nte864 function generator schematic

If you have familiarity with any microcontroller, there is another way you could do the waveform generator, relatively simple. First of all, all kind of microcontrollers have PWM outputs. So it is easy to generate square waves. If you put a second order low pass filter in one of this outputs and then do some internal look up table you could change the duty cycle, hence change the dc output after filtering the PWM signal. In that way you could do a sinewave generator. If you want to output ramps, you, could just increase little by little the duty cycle and if you do some logic you can do triangles waveforms in the same way. Actually you could do any kind of waveform with this procedure. Look in the web for the keywords PWM, Sine, function generator, there are plenty of articles explaining this kind of circuit.

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