Power sensor signal conditioing

[audioguru]

Why are you connecting pin 5 to pin 7 then through a resistor to the negative supply?

 

[charbel89]

Power sensor signal conditioning

Why are you connecting pin 5 to pin 7 then through a resistor to the negative supply?

I am trying to replicate what circled in red in the image. I think I got it wrong somehow. Maybe it should be as in the updated image.

You also might want to supply power to the CA3140

Power supply to the CA3140 is a +5 V I think



Thanks

 

[audioguru]

The schematic has a 10k pot between pin 1 and pin 5 with the slider of the pot connected to the negative supply.

You have a 10k (or 1k?) fixed resistor between pin 5 and pin 7 and pin 5 is connected to the negative supply.

 

[charbel89]

Thanks Audioguru,

Please disregard the actual resistor shown this is just for illustration. I am trying to understand how it should be connected on a breadboard and I did not realise it was a pot/slider (not too sure of the actual technical meaning).

Please elaborate on what pot/slider mean.

I am also a bit worried about the connection highlight in red in the circuit image.

A breadboard drawing of how they should be connected will be nice.

Thanks a lot

EDIT:
I found this potentiometer on Maplin. So to have this connected will it matter which wire goes where?



Regards

The schematic has a 10k pot between pin 1 and pin 5 with the slider of the pot connected to the negative supply.

You have a 10k (or 1k?) fixed resistor between pin 5 and pin 7 and pin 5 is connected to the negative supply.

 

[audioguru]

You don't understand what is a potentiometer. Look it up in Google.

You show a precision trimpot with a screw that turns 10 times or 22 times around. You cannot see where it is adjusted.

I show less expensive but good quality trim pots with an adjustment of about 300 degrees so you can see where it is adjusted.

The middle pin is the slider. Your circuit has an ordinary resistor that does not have a slider.

 

[charbel89]

What would we do without google .

I already googled it and thats how i found out that pot was refering to potentionmeter.

Here is an updated drawing.

You don't understand what is a potentiometer. Look it up in Google.

You show a precision trimpot with a screw that turns 10 times or 22 times around. You cannot see where it is adjusted.

I show less expensive but good quality trim pots with an adjustment of about 300 degrees so you can see where it is adjusted.

The middle pin is the slider. Your circuit has an ordinary resistor that does not have a slider.

 

[audioguru]

What would we do without google .

I already googled it and thats how i found out that pot was refering to potentionmeter.

Here is an updated drawing.

Good. The offset adjust trimpot is connected correctly.

 

[charbel89]

Thanks.

What about this drawing are they equal?

Good. The offset adjust trimpot is connected correctly.

 

[audioguru]

You connected the polarity of the 4.7uF capacitors backwards.

 

[ericgibbs]

Thanks.

What about this drawing are they equal?

hi,
As pointed out by agu,the 10uF are reversed, if you apply 9V to the board they could explode.

Why have you started such a complex project without first getting the basic knowledge regarding components.?

I would suggest if you are interested in building projects you start studying basic electronics.
This is not intended as a 'put down', but doing this project by asking every simple step without understanding each step will not help you to learn.

If you feel you must proceed with this project, forget for the time being the clamp, the AD763 and the PIC and complete the CA3140 amplifier.
You can use a pot as a mVolt dc test source.

Once you have got that working, program the PIC to read the voltage coming from the CA3140.

 

[charbel89]

Thats a good question.

It was not my intention to go as far as I did. I thought it would be a simple easy job. Obviously I was wrong and it got complicated gradually.

I also assumed this is a problem that has already been solved and the solution should be readily available, so I did not give too much attention to the transducer-AD736-PIC part and implemented the software client/server simulating the input signal to the PIC, which works fine.

I now decided to tackle the final part. This is becoming a project on its own

At this point it will be a total waste to stop.

With regards to the capacitors the ones I have, do not have any + or - signs so I initially assumed it will be ok to plug them.

The ones in the diagram obviously show a +++ sign but not the ones I am actually using.

I will try this evening to post pictures of my capacitors, the spot and the board I am using.

I ordered the CA3140 and a new larger breadboard, with new correct size capacitors. should be arriving in the next couple of days.

I am looking at this pot for pin 2 to 6 any recommendations? Also what happens to the 3rd pin in this case? one end is connected to 2 the other to 6 and the 3rd to..?

Potentiometers - Rotary | Farnell UK

Pin 1 to pin 5:
Potentiometers - Rotary | Farnell UK


Thank you for your patience in helping me to solve my electronics component problems and I must say without your support I would not have gone this far.

hi,
As pointed out by agu,the 10uF are reversed, if you apply 9V to the board they could explode.

Why have you started such a complex project without first getting the basic knowledge regarding components.?

I would suggest if you are interested in building projects you start studying basic electronics.
This is not intended as a 'put down', but doing this project by asking every simple step without understanding each step will not help you to learn.

If you feel you must proceed with this project, forget for the time being the clamp, the AD763 and the PIC and complete the CA3140 amplifier.
You can use a pot as a mVolt dc test source.

Once you have got that working, program the PIC to read the voltage coming from the CA3140.

 

[ericgibbs]

hi,
OK understood.

Dont buy those pot types, Ill post a sketch later[ bit busy at the moment]
showing the pots more clearly.

 

[ericgibbs]

hi,

Look at this sketch showing the pots.

Also study the links.

**broken link removed**

**broken link removed**

 

[charbel89]

Thanks Eric.

Is pin 7 supposed to be pin 6?

hi,

Look at this sketch showing the pots.

Also study the links.

**broken link removed**

**broken link removed**

 

[ericgibbs]

Thanks Eric.

Is pin 7 supposed to be pin 6?

Well spotted.! For 7 read 6. Pin 7 is of course +5V.

EDIT:
Dwg error corrected.

 

[charbel89]

I thought this was a test for me

Anyway here are the pictures of what I have and this is without the amplifier.

I hope they are clear enough.

Well spotted.! For 7 read 6. Pin 7 is of course +5V.

EDIT:
Dwg error corrected.

 

[ericgibbs]

hi,
Looked at the pics.

Remember you are working with millivolt level ac signals.

You must keep the interconnecting wires as short as 'reasonable' else you will pick up mains em radiation which will give reading errors.

I would recommend that you build the CA3140 amplifier, this will increase the voltage that is output from the AD736.
You can use your dc meter to check the output.

Use a pot about 10k or 20K as a test input source for the amplifier.

I'll attach a sketch.

 

[charbel89]

The connector wires are 7CM in length.

I do get quiet a bit of em radiation, and now that I have my (better) multimeter I can test the AC output at millivolts.

Once I am done with the proof of concept/prototype on the breadboard I want to see if I can get a PCB printed.

I did some background research and it seems simple enough to do with a laser printer (at least with the kits available from Maplin).

Only thing that I know I will struggle with is the actual drawing of the PCB.

I am at the moment waiting for the CA3140 to arrive.

Thanks a lot.

Charbel.

hi,
Looked at the pics.

Remember you are working with millivolt level ac signals.

You must keep the interconnecting wires as short as 'reasonable' else you will pick up mains em radiation which will give reading errors.

I would recommend that you build the CA3140 amplifier, this will increase the voltage that is output from the AD736.
You can use your dc meter to check the output.

Use a pot about 10k or 20K as a test input source for the amplifier.

I'll attach a sketch.

 

[Nigel Goodwin]

I would suggest you try building it on Veroboard, far better than using breadboard - particularly with the massive long wires you've used.

 

[charbel89]

Thanks Nigel,

I will look into this. I am placing an order from RS-components so I will check their range.

I would suggest you try building it on Veroboard, far better than using breadboard - particularly with the massive long wires you've used.