Need help with my final year project...

[be80be]

I looked at what your saying but ground is ground And I didn't see you feeding the op-amp but 5 volts. You don't have spit rails

 

[navarro_boyz]

I am using op 295 op amp in my circuit.So, let's say i put in a LM358 op amp into the circuit.Will it work?

 

[be80be]

There not the same but they should work looking at the data 295 is good 75kz the 358 1 mhz it uses more power then 295 test it and see.

 

[navarro_boyz]

Is the any calibration needed for my circuit?

 

[be80be]

It should work but why do you want to change? can't find a Op295

 

[navarro_boyz]

Is there any calibration needed for my circuit?

 

[navarro_boyz]

If the cut off frequency of the first and second amplifier is 2 hz, so the corresponding capacitor value for the first amp would be 80nF and for the second amp would be 142nF. So, the nearest the ceramic capacitors value would be 100nf, is it?

 

[be80be]

I would go with the 295 to save any head aches I have the parts to build this with both the 295 and 358 I try it and let you no how they do if you want.

 

[navarro_boyz]

Dear Be80be,

I have some questions for you.

1.The output from the pin7 (op amp) entering the pin6(RB0) pic is in analogue or digital input?

2.If the cut off frequency of the first and second amplifier is 2 hz, so the corresponding capacitor value for the first amp would be 80nF and for the second amp would be 142nF. So, the nearest the ceramic capacitors value would be 100nf, is it?

3.What is the purpose of the pot 10Kohm at the output of the first amplifier?

4.Is there any calibration needed in the circuit?

5.How do i get the frequency and phase response of the amplifier with filter circuits?

View attachment 60545

6.I have some oscilloscope output from the pc based software(SCOPE).Can you give me your opinion?

This is the output of the op amp after all the filtering before going through the pic
View attachment 60546

This is the output of the first op amp before going to the next op amp
View attachment 60547

Thank you.

 

[be80be]

1 it's conditioned for digital read so you can count it.
2 They use a 100nf and resistors to set the filter.
3 set the gain
4 the pot for best signal
5 Read the data sheet there some math in there you need to no based on input resistance and your RC filiter.
6 It looks like your getting nice beats. Like about 60 a minute

 

[navarro_boyz]

Dear Be80be,

I don't understand the answer for question 1, 2 and 5. For question 5, couldn't I get the frequency and phase response from the simulation software or computer based software?

 

[be80be]

1 it's conditioned for digital read so you can count it. The RB0 is counting the beats you conditioned the pulse beat for a digital read. It's digital



2 They use a 100nf and resistors to set the filter. They picked a 100nf it was close and then picked resistors to make RC filter for range needed.


5 Yes you could if ISIS has the tester for it

It tells you in the code that your reading digital , this is counting the high pulse.

DO 3 times
Get count in 10 seconds
Count = 6 * Count
Sum = Sum + Count
ENDDO

I wish i had a full copy of ISIS to much cash for my blood

 

[navarro_boyz]

so, are you saying that what i have said in the question 2 is correct or they pick the 100nf first before selecting the resistors value so that it will be 2hz?

 

[turan76]

that's true