Why do you think that circuit does not work when I use single Ic ?

Hi demir,
When using a single IC on a bread board, one possibility is the close proximity of the components, around the single IC which may cause some instability, it is difficult to be sure.

How long is the Piezo 'ringing' at 40kHz after the 10 transmission pulses?

I stil can not measure distances under 60cms, this time mostly due to overgaining.

This is why in some echoing measurement systems a 'swept' gain amplifier is used.
ie: the gain is slowly increased after the TX pulse time.

E

 

Hi demir,
When using a single IC on a bread board, one possibility is the close proximity of the components, around the single IC which may cause some instability, it is difficult to be sure.

How long is the Piezo 'ringing' at 40kHz after the 10 transmission pulses?

I stil can not measure distances under 60cms, this time mostly due to overgaining.

This is why in some echoing measurement systems a 'swept' gain amplifier is used.
ie: the gain is slowly increased after the TX pulse time.

E

The first long peak part in the picture is high gained osscilating affer transmission part. After İt is perfectly readable but I can track the echo into 2ms I guess eventhough İt is hard to.
I have not researched much about sweep gain but would using bjt as variable impedance be usefull ?

 

Hi dem,
Post #77 scope image, is the timescale set to 1mSec per division?
I assume the Blue trace is the TX pulses.
So what is the time delay between the TX pulse and RX measured in mSecs?

E

 

Hi dem,
Post #77 scope image, is the timescale set to 1mSec per division?
I assume the Blue trace is the TX pulses.
So what is the time delay between the TX pulse and RX measured in mSecs?

E

Yes It is, the delay is 8.72ms. The object echo returns from is the roof that is 1.44 meters away from the transducer.
x = 0.00872*330/2 , x= 1.4388m
It corrects our measurement.

 

HI dem
The 330m/Sec at 0C degrees, room temperature ~340m/Sec

E

 

HI dem
The 330m/Sec at 0C degrees, room temperature ~340m/Sec

E
View attachment 327446

Hi Eric, I've tested if echo pulse moves with the distance by moving a large box over transducer and yes It does move.
Assuming the sound of speed is around 350m/s and return of the pulse is around 8.7ms it seems pretty correct isn't it ?

 

Coupling between isolated op-amps in a two-device chip would be due to both the close proximity and also using a common set of power connections. And the signal level also has a bit to do with it. Seldom mentioned, but certainly a source of some head-scratching results. So a very good call on separating them.!

 

Hi, I made a simple design to control the gain of an op-amp and when I vary the voltage between 0-5 in V3 , I can control the gain , but I doubt if I am overcomplicating it. When I vary the voltage between 0-5 in V3 , I can control the gain. I also doubt if I can put 1-5V on input since MCU does it by pwm as I remember.
I also thought using something like demux for switching between 2 resistors for gain that is managed by MCU.
Can you review it ?

 

Hi demir,
Please post your LTS asc file, saves me time.
E

 

Here it is.

 

Hi demir,
Please post your LTS asc file, saves me time.
E

I will also research about Automatic Gain Control. IRFZ44N is so powerfull but also it is huge.
Vds value is under 0 voltages I doubt if I drive nmos right.

 

Hi dem,
This is it with a minor modification, there is some increase in gain with time.
E

 

Hi dem,
This is it with a minor modification, there is some increase in gain with time.
E
View attachment 327477

Hi eric, I've checked your upload and found out anything differs is you set the V3 as PWL. In my upload , I meant that V3 will be set by mcu but since arduino can not give any output voltages over 5v , I used opamp to be able to set the voltage towards 12.
So did you find my solution usefull ?

 

I made an lowpass filter with an diode to adjust dc voltage between 0-5 volts but in simulation it does not work can you review ?
I wonder if it is because of gate charges of the IRFZ44N.

 

Hi , I've made and comparator built considering the osilloscope output I shared.
I add both circuit image, .asc file and the output.

 

Hi demir,
Your simulation works OK, I have suggested a modification to the Vref.
E


BTW: Checkout this link, ref echo attenuation rate, it will give you an idea about a swept gain profile.

https://pressbooks.pub/sound/chapter/intensity-and-distance-april-2019-version/

 

Hi demi,
Ref your post #94.
Run this asc file sim, note the added circuit, at the bottom left-hand corner of the diagram.
E

 

Hi demi,
Ref your post #94.
Run this asc file sim, note the added circuit, at the bottom left-hand corner of the diagram.
E
View attachment 327529

Sir please recheck it , It does not amplify the signal.

 

hi demi,
Look at the PWL voltage limits in my added circuit compared to yours.
Also change the limits in my circuit to your values and see what happens.

E

 

hi demi,
Look at the PWL voltage limits in my added circuit compared to yours.
Also change the limits in my circuit to your values and see what happens.

E
View attachment 327532

Hi , I could not have signal output anyways and I wonder there is vg and VG in the circuit and vg,vd couple is nowhere else. So I could not understand the purpose of nmos built here.
I would liked to smooth the pulses to have dc voltage since arduino can not give voltages like 2 3 4 but my built has not worked.