Ultrasonic >100w amp for vibration exprmt...

[krazatchu]

So instead of working on the generator today.. I decided to play with that c300 that you linked too...

I tried feeding it with a variety of signals... but I'm getting out, almost exactly what I put into it...

...square wave is a bit distorted.. the sine looks great...

The input and output perfectly overlap on the scope...

Where is the gain???

Confused,
Michael

PS.. i swapped the mj15003/4 to mj15001/2 ... didnt have the spice model... and i used a 1n4752a for the 33v 1 watt zener...

 

[krazatchu]

Goldsphere~~

I was just re-reading the posts, this time with my eyes open~~

I was under the impression that Chladni plates needed a sine wave to reduce the other harmonics...

If I'm wrong, that would be great....

The plate... It's not exactly thin... (~310mm x 140mm x 18mm)... almost 2 cm thick aluminum...

And here is the FEA sim @ ~19,650 Hz ...

Michael

 

[Goldsphere]

Well, I'm not sure about that. The frequencies are in the audible range though, at least for the less complex patterns. Here is a youtube clip of the effect.
https://www.youtube.com/watch?v=MPcJbb5Qfj0
It seems to me that a square wave would do the same that a sine wave would do in this circumstance because essentially you are just hitting the plate with a large compression wave. 18mm seems really thick to me, might dampen the wave a bit.

 

[audioguru]

I decided to play with that c300 that you linked too...

I tried feeding it with a variety of signals... but I'm getting out, almost exactly what I put into it...

...square wave is a bit distorted.. the sine looks great...

The input and output perfectly overlap on the scope...

Where is the gain???

The voltage gain is R14/R15= 10k/330= 30.3.
The spec's say that 1.2V RMS input gives 200W into 8 ohms output (40V RMS) but the input realy needs to be 1.32V RMS.

 

[krazatchu]

Audioguru.... thanks... something was wrong with those 2 caps c7 and c8.... took them out and now ~~I got gain~~
Now to figure out whats wrong with them...

Goldsphere.... I'll have to do some homework on that... I assumed that if I was driving extra harmonics the total power at the specific frequency would be lower... I'll find out and post my conclusions...

Michael

 

[krazatchu]

The caps were touching but not connected... silly oversight...

 

[audioguru]

C7 and C8 are back-to-back electrolytics. Your simulator doesn't know about them. Remove one.