Pressure Sensor alarm with PIC16F877A to activate the bulb

[jean12]

yes I did it but I found that V+ =V-

 

[Venkadesh_M]

yes I did it but I found that V+ =V-

Is there is any problem using one opamp??

 

[snishanth512]

Post the Circuit that you have designed now.

And the results you got from the circuit.

The data you mentioned above is not clear.

 

[jean12]

Hello ,consider this circuit I used that bloc of op amp to amplifier the signal from the pressure sensorhttps://1.bp.blogspot.com/-2APFydOOJdc/UES57M_yENI/AAAAAAAAACI/znkWj9EMGYU/s640/11.png

 

[Venkadesh_M]

using Instrumentation amplifier is fine.....

 

[mithun mohan]

hi jean,

try this circuit....

 

[Venkadesh_M]

hi jean,

try this circuit....

subtractor is simple and best...

@jean12
Now you have to find the power supply and real output offset voltages....

 

[pinout]

Hi Jean12, The issue you have is your circuit is AC coupled at the input, you need to modify it in that area for DC coupled.
Replace the input "Cs" with resistors, but I'm not sure to what yet.

Perhaps someone else will suggest?

Currently your circuit may respond to varying the pressure at a frequency, **** and blow fast!!!

 

[jean12]

So what may I do??

 

[Venkadesh_M]

Hi Jean12, The issue you have is your circuit is AC coupled at the input, you need to modify it in that area for DC coupled.
Replace the input "Cs" with resistors, but I'm not sure to what yet.

Perhaps someone else will suggest?

Currently your circuit may respond to varying the pressure at a frequency, **** and blow fast!!!

;-) what is that higher frequency and how much it will be??

- - - Updated - - -

So what may I do??

I believe there will be no such a problem........

 

[pinout]

The circuit you present is a 'swimming pool alarm', it is designed to only measure pressure changes such as waves, NOT the actual pressure, hence the AC coupling not to measure the actual pressure. Only the disturbances in pressure will be measured.

So as a comparison, it's a bit like measuring a DC power supply where the meter is AC coupled and hence will only measure the ripple on the supply, not the slowly changing actual voltage.

 

[Venkadesh_M]

The circuit you present is a 'swimming pool alarm', it is designed to only measure pressure changes such as waves, NOT the actual pressure, hence the AC coupling not to measure the actual pressure. Only the disturbances in pressure will be measured.

So as a comparison, it's a bit like measuring a DC power supply where the meter is AC coupled and hence will only measure the ripple on the supply, not the slowly changing actual voltage.

I thought you talking about subtractor....

 

[jean12]

So what can I do for making my circuit operating,I would like to apply a compressor on the input of the sensor MPX2100.

Thanks.

 

[Venkadesh_M]

construct the subtractor circit.......

 

[jean12]

Do you think that the substractor amplifier will help,How will I make the ADC after reading a small value like the one here we have 1mv for 1KPa.

Please help.

 

[Venkadesh_M]

That is not only subtractor It also amplifies with the gain of 1M/33k . .

 

[pinout]

Did you follow up these two Application notes?

They both provide Discrete op amp interfacing designs and lots of design detail.

Have a look at AN1315 and AN1324 on the Freescale website
**broken link removed**
just search for MPX2100 if its not there by default or the app note numbers. There's lot more as well.

Excellent material from the manufacturer.....

 

[jean12]

Hello,for using a sensor as a switch I searched for other useful circuit without special op amps (which I don't have)the circuit with comparator I get from the net it is operating like a switch and I think it can be useful;please help to think far on it.

see the linkhttp://www.datasheetdir.com/Pressure-Switch-Design-With-Semiconductor-Pressure-Sensors+Application-Notes


I implemented and after those two first op amps I got 0.59985V at the output(using LM324);I want to add a comparator;can you please help me to implement this is the circuit below on the indicated link which will help me to do the job??

Thanks.

 

[Venkadesh_M]

By using comparator you can adjust the ref voltage by hardware only if you want to change the operating presser means you have adjust the ref value.... And also you can directly give the input to a digital pin....

Is it a matter to getting an opamp??

 

[jean12]

So how will I know that the pressure I have is in this boundary (that is what I want);

I for example the pressure is 15Pa I have to activate the bulb,or for example if the pressure (P):

10<=p<=15 as example activate a bulb on PIN_C5 of the PIC16F877A
15<P<=20 activate a ventilator on PIN_C1 of the PIC of the PIC16F877A

Programming is not matter;the problem is having the variable values as long as I apply any pressure type on the sensor and so in CCS C I can program;the electronic which has to be used for getting those changes which we have to evaluate in the program is ;just that electronic block is my problem.

Thanks.