need liquid drop sensor schematic

[loup-garou]

hi again,

thank you very much Roff for explaining me the schematic (I did appreciate it ), thank you also rjvh for proposing me those alternatives (I admit that I did not understand all, but I'll return to them in my next post ),thank you Mikebits for your link (I'll look into it and I'll come back later).

here is the simulation file of the two stage PBF (I did add the second), my input is sine having V amplitude, 10V peak and 3.5 V RMS. and by now the frequency respoinse is totally wrong (bandwidth , amplitude,...)

 

[rjvh]

Hi loup garou

I found a schematic of a rain meter based on counting droplets

i marked the puls givving part of it (generator) and that you could process further in a PIC

also the mechanical details to build a droplet creator would be handy if you don't have that already

the arows in the sensor enclosure drawings represent the beam that will be broken when a droplet drips down through the chanel

sucsess

Robert-Jan

 

[Mikebits]

The link I provided above sounds like just what you were asking for. An IV drip meter with a Micro control. All the signal conditioning is done in the software. The design uses the MCS51 family but I am sure you could adapt the principle to a PIC.
The schematic from the link is attached.

 

[Roff]

hi again,

thank you very much Roff for explaining me the schematic (I did appreciate it ), thank you also rjvh for proposing me those alternatives (I admit that I did not understand all, but I'll return to them in my next post ),thank you Mikebits for your link (I'll look into it and I'll come back later).

here is the simulation file of the two stage PBF (I did add the second), my input is sine having V amplitude, 10V peak and 3.5 V RMS. and by now the frequency respoinse is totally wrong (bandwidth , amplitude,...)

Your copy of the schematic must be better than what you posted. I can't read the values, so I can't simulate it. Can you post a more legible schematic, at least of the filters?
Or maybe at this point, since you have circuits with microcontrollers, the response is irrelevant. If so, don't bother.

 

[loup-garou]

hi guys,

Excuse me for not coming yesterday (I had some problems to connect to internet)


@Mikebits & rjvh: I have dowloaded your files, and I'm viewing them now.
thanks a lot for taking time to find them for me.


@Roff: here is a capture screen of the schematic taken from ISIS for the both stages, I have to say that I also have some difficulties to determine the exact values since the original copy is not so clear too. I also included, in the attached files, the frequency response of the First stage (BPF 1).

TLC2252 is an equivalent of ICL 7641 (as I think) which I did not find in the ISIS Library.

 

[Roff]

hi guys,

Excuse me for not coming yesterday (I had some problems to connect to internet)


@Mikebits & rjvh: I have dowloaded your files, and I'm viewing them now.
thanks a lot for taking time to find them for me.


@Roff: here is a capture screen of the schematic taken from ISIS for the both stages, I have to say that I also have some difficulties to determine the exact values since the original copy is not so clear too. I also included, in the attached files, the frequency response of the First stage (BPF 1).

TLC2252 is an equivalent of ICL 7641 (as I think) which I did not find in the ISIS Library.

Something is wrong with your simulation. I suspect it doesn't have power supplies.
You show R1 and R6 as 10k, when they are pretty clearly 1.8k on the original schematic. attached are the results of my simulation, along with the .ASC file, in case anyone wants to run it in LTspice.

 

[loup-garou]

Something is wrong with your simulation. I suspect it doesn't have power supplies.
You show R1 and R6 as 10k, when they are pretty clearly 1.8k on the original schematic. attached are the results of my simulation, along with the .ASC file, in case anyone wants to run it in LTspice.

thanks a lot Roff for taking time to simulate the filter and correcting my values .
it's now much better after adjusting the resistors values (attenuation ~0 and peak frequency ~1.2kHz) but it's still not perfect. the power supply that I am using for the Op Amps is 5V-GND, may this has a particular effect in the frequency response ?

 

[Roff]

thanks a lot Roff for taking time to simulate the filter and correcting my values .
it's now much better after adjusting the resistors values (attenuation ~0 and peak frequency ~1.2kHz) but it's still not perfect. the power supply that I am using for the Op Amps is 5V-GND, may this has a particular effect in the frequency response ?

I suspect that having the 820 ohm resistor R5 tied to the bias network (vcc/2) is screwing up the voltage. The bias network gets connected to GND through the R5 and the simulation source voltage. Try AC-coupling your source through 100uF (in the simulation only). Alternately, you could connect the bottom ends of R5 and R6 to GND instead of vcc/2.
TLC2252 is pretty low bandwidth for this application. I tried it in the sim, and it worked, but I think the gain peak at 1.2kHz was somewhat lower, and the bandpass peak frequency was shifted down a little, than with the faster generic model I used.