Hi,

I need to create a sine wave output of about 300Hz with ramped AC output starting at ~ 0.01 V p-p increasing to 10 V p-p over about ~13 seconds

I have found some circuits for ramp functions and also for sine wave generators but I have not been able to couple the two together with any success.

This is my first electronics project in many years, so I am still pretty low on the learning curve.

Any suggestions would be most appreciated.

Many Thanks

 

Just to open the door: Start with Op Amp. fed with your 300 Hz. oscillator- maybe 1V PP. Use a LED to CdS.
photo coupler for Op Amp feedback. Use a 555 ramp generator to drive the LED. Input resistor around 100K,
almost dark coupler feed back 1M= output of about 10V PP. Drive LED harder & feedback drops to 1k , output about .01 V PP ??

 

There must be an op-amp on the market with a gain set by an external voltage (if there isn’t one, I’ve just invented it).

Feed the 300Hz sine wave into the op-amp and supply the op-amp gain input voltage via a suitable resistor charging a suitable capacitor to give the required gain ramp time.

 

Transconductance OpAmp to create a PGA and a Ramp Generator might
be fruitful.

https://www.onsemi.com/pub/Collateral/NE5517-D.PDF

http://www.ti.com/lit/ds/symlink/lm13700.pdf

Another way use a multiplier and modulate the sine that way.

https://www.analog.com/media/en/tra...ltiplier_Applications_Guide.pdf?doc=AD532.pdf

Page 15 of the above.


Regards, Dana.

 

I did find some variable amps that should work, but the cheapest I found (LMH6505MM/NOPB) is about $6.50/ea in one-up quantities.
is that within your budget?

 

An alternative approach as the frequency is fixed is to generate a ramped square wave which would be easier and filter the output with a LC filter (Or you could use an active filter.) tuned to 300 Hz.

Les.

 

Or use a digital pot in signal path. Drive it with a counter or
if I2C interface a low cost UP like an ATTINY UP. The ATTINY
could also generate the ramp via use of PWM. You can also use
table lookup technique in ATTINY or Arduino to gen the sine wave
via PWM modulation.

https://web.csulb.edu/~hill/ee470/Lab 2d - Sine_Wave_Generator.pdf


Or a multiplying DAC -

http://www.ti.com/lit/an/snaa097/snaa097.pdf

Regards, Dana.

 

Hi,

I need to create a sine wave output of about 300Hz with ramped AC output starting at ~ 0.01 V p-p increasing to 10 V p-p over about ~13 seconds

I have found some circuits for ramp functions and also for sine wave generators but I have not been able to couple the two together with any success.

This is my first electronics project in many years, so I am still pretty low on the learning curve.

Any suggestions would be most appreciated.

Many Thanks

Use a microchip pic + dac + opamp as buffer
output Amplitude = offset+ A . sin(t) A amplitude .
or when you need a separate DAC remove offset and use opamp to create an offset.
300 is slow and no problem to calculate or use a table.
Link a to ramp as function of period or as function of t. ( last one allows you to create a periodic wave form)
doing t in big steps you are able to build different wave forms like triangle ++

Picbuster