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EAGLE User Chat (English) Could someone check my design?
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Related

Could someone check my design?

jacob-t
jacob-t over 9 years ago

Hi Guys

I'm totally new to this. I'm trying to build a 4 channel opamp (boost my signal about 100x)

I'm hoping someone has the time to quickly check my design and see if it makes sense and perhaps let me know how to improve it.

 

Thanks

Jacob

Attachments:
opamp.zip
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  • jacob-t
    jacob-t over 9 years ago in reply to kikoun +1
    The opamp is meant to amplify a 7-50mV signal around 100 times so I can reliably read it with a National Instruments DAQ. I'm sorry I'm such a newbee, any and all help is really appreciated! I'll try and…
  • kikoun
    kikoun over 9 years ago in reply to jacob-t +1
    Hmmm not sure i got the capcitors right. ;-) Partially... For the 5µF capacitor: it's connected correctly in schematic, but I'm not sure you will found a value of 5µF, but a value of 4,7µF, 10µF, 22µF…
  • kikoun
    kikoun over 9 years ago in reply to jacob-t +1
    Hi, That last design is better, the ground plane is OK.. You remove the big capacitor (your 5µF) I suggested to check the value and the package, but not t remove it ? If it was one of my design I would…
Parents
  • autodeskguest
    autodeskguest over 9 years ago

    Am 07.10.2015 um 14:02 schrieb Jacob Thastrup:

    Hi Guys

    I'm totally new to this. I'm trying to build a 4 channel opamp (boost my

    signal about 100x)

    I'm hoping someone has the time to quickly check my design and see if it

    makes sense and perhaps let me know how to improve it.

     

    Thanks

    Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162669

     

    Attachments:

    opamp.zip

     

     

    No capacitors?

     

    --

    Mit freundlichen Grüßen / With best regards

     

    Joern Paschedag

     

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  • jacob-t
    jacob-t over 9 years ago in reply to autodeskguest

    You mean to filter the input?

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  • kikoun
    kikoun over 9 years ago in reply to jacob-t

    Hi,

     

    At least capacitors should be added on the supply...

    I don"t know the purpose of your circuit but you should add at least a small one capacitor (10 to 100 nF) placed near the power supply input pins of the LM324, and a electrolytic caacitor (few µF) rignt after the supply input connector.

    En large 24V supply trace, and for the GND you can enlarge the trace or better add a GND plane (polygon).

     

    Guillaume

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  • jacob-t
    jacob-t over 9 years ago in reply to kikoun

    The opamp is meant to amplify a 7-50mV signal around 100 times so I can reliably read it with a National Instruments DAQ.

     

    I'm sorry I'm such a newbee, any and all help is really appreciated! I'll try and add some capacitors to the diagram and see if I can work out how to add a GND plane :-)

     

    I'll be back ;-)

     

    Thanks

    Jacob

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  • jacob-t
    jacob-t over 9 years ago in reply to jacob-t

    Hmmm not sure i got the capcitors right. ;-)

     

    How's this version?

     

    Thanks again

    Jacob

    Attachments:
    test4.zip
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  • autodeskguest
    autodeskguest over 9 years ago in reply to jacob-t

    Am 08.10.2015 um 14:43 schrieb Jacob Thastrup:

    Hmmm not sure i got the capcitors right. image

     

    How's this version?

     

    Thanks again

    Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162771

     

    Attachments:

    test4.zip

     

     

     

    Where is your attachment???

    Anyway I didn't like the many junctions and the separated connectors in

    the schematic,

    so I messed around in your design (as an example of course). Same went

    for the board image

    I also changed the width of the tracks, because I suppose you want to

    etch yourself...

     

    --

    Mit freundlichen Grüßen / With best regards

     

    Joern Paschedag

     

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Reply
  • autodeskguest
    autodeskguest over 9 years ago in reply to jacob-t

    Am 08.10.2015 um 14:43 schrieb Jacob Thastrup:

    Hmmm not sure i got the capcitors right. image

     

    How's this version?

     

    Thanks again

    Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162771

     

    Attachments:

    test4.zip

     

     

     

    Where is your attachment???

    Anyway I didn't like the many junctions and the separated connectors in

    the schematic,

    so I messed around in your design (as an example of course). Same went

    for the board image

    I also changed the width of the tracks, because I suppose you want to

    etch yourself...

     

    --

    Mit freundlichen Grüßen / With best regards

     

    Joern Paschedag

     

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Children
  • jacob-t
    jacob-t over 9 years ago in reply to autodeskguest

    Hi Joern

    Maybe I'm getting it wrong. But I don't see any files from you?

    Thanks

    -Jacob

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  • autodeskguest
    autodeskguest over 9 years ago in reply to jacob-t

    Am 08.10.2015 um 17:38 schrieb Jacob Thastrup:

    Hi Joern

    Maybe I'm getting it wrong. But I don't see any files from you?

    Thanks

    -Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162826

     

     

    I attached it but I suppose it is the glorious interconnection between

    the newsgroup and element 14 that never works since years...

    Next try now...

     

    --

    Mit freundlichen Grüßen / With best regards

     

    Joern Paschedag

     

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  • autodeskguest
    autodeskguest over 9 years ago in reply to autodeskguest

    Am 09.10.2015 um 10:42 schrieb Joern Paschedag:

    Am 08.10.2015 um 17:38 schrieb Jacob Thastrup:

    Hi Joern

    Maybe I'm getting it wrong. But I don't see any files from you?

    Thanks

    -Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162826

     

     

    I attached it but I suppose it is the glorious interconnection between

    the newsgroup and element 14 that never works since years...

    Next try now...

     

     

    No, sorry it  didn't go throu, maybe because I'm not registered at

    element14 .

    And I'm not interested to register there.

     

    --

    Mit freundlichen Grüßen / With best regards

     

    Joern Paschedag

     

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  • autodeskguest
    autodeskguest over 9 years ago in reply to autodeskguest

    On 09.10.2015 11:12, Joern Paschedag wrote:

    Am 09.10.2015 um 10:42 schrieb Joern Paschedag:

    Am 08.10.2015 um 17:38 schrieb Jacob Thastrup:

    Hi Joern

    Maybe I'm getting it wrong. But I don't see any files from you?

    Thanks

    -Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162826

     

     

    I attached it but I suppose it is the glorious interconnection between

    the newsgroup and element 14 that never works since years...

    Next try now...

     

     

    No, sorry it  didn't go throu, maybe because I'm not registered at

    element14 .

    And I'm not interested to register there.

     

     

    You can find them here

    http://www.eaglecentral.ca/forums/index.php/t/51848/5abd43c14367c14cffef482390e897d4/

     

     

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  • jacob-t
    jacob-t over 9 years ago in reply to autodeskguest

    Once again thank you guys!!

    Guillaume, thank you for the explanation it really helps!

     

    I've added a ground plane to Joern's design... does that make sense?

     

    I hope you can see the attached file..otherwise I'll go register at eaglecentral as well.

    -Jacob

    Attachments:
    test5.zip
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  • kikoun
    kikoun over 9 years ago in reply to jacob-t

    Hi,

     

    That last design is better, the ground plane is OK.. You remove the big capacitor  (your 5µF) I suggested to check the value and the package, but not t remove it ? If it was one of my design I would  put a 10µF electrolytic capacitor between GND and +24V, just right after the supply connector...

     

    Nice work ....

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  • autodeskguest
    autodeskguest over 9 years ago in reply to jacob-t

    Am 09.10.2015 um 18:34 schrieb Jacob Thastrup:

    Once again thank you guys!!

    Guillaume, thank you for the explanation it really helps!

     

    I've added a ground plane to Joern's design... does that make sense?

     

    I hope you can see the attached file..otherwise I'll go register at

    eaglecentral as well.

    -Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162904

     

    Attachments:

    test5.zip

     

    You should go there anyway. It is just the better link to the cadsoft

    newsgroups image

    They don't have trouble with attachments (as you have seen).

    BTW my "design" was just a suggestion.

    Maybe you should add an electrolytic capacitor in general and foresee

    some holes to screw this print somewhere.

     

    --

    Mit freundlichen Grüßen / With best regards

     

    Joern Paschedag

     

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  • autodeskguest
    autodeskguest over 9 years ago in reply to jacob-t

    Jacob Thastrup wrote on Fri, 09 October 2015 12:34

    Once again thank you guys!!

    Guillaume, thank you for the explanation it really helps!

     

    I've added a ground plane to Joern's design... does that make sense?

     

    I hope you can see the attached file..otherwise I'll go register at

    eaglecentral as well.

    -Jacob

     

    --

    To view any images and attachments in this post, visit:

    http://www.element14.com/community/message/162904

     

    Attachments:

    test5.zip

     

     

    I think there should be a ground connection for each channel. In other

    words, you will need 3-pin instead of 2-pin connectors. Otherwise your only

    ground connection is through the power supply connector. The ground pin

    should be between each input and output pin. I agree with others that you

    should have a cap across the power supply terminals. Also, on your layout,

    if you switch to a finer grid (i.e. 10 mil aka(0.01")), you can move some

    traces slightly and improve the ground plane near the left end of the chip

    (also changing the polygon width to 12 mils helps). If you swap the ends of

    R5 and R6, then you can have a single trace for OUT3, instead of 2 traces.

    You can do the same thing for the other channels.

     

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

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  • jacob-t
    jacob-t over 9 years ago in reply to kikoun

    Guillaume barrey[1

    wrote on Sat, 10 October 2015 05:53]Hi,

     

    That last design is better, the ground plane is OK.. You remove the

    big

    capacitor  (your 5µF) I suggested to check the value and the

    package,

    but not t remove it ? If it was one of my design I would  put a 10µF

    electrolytic capacitor between GND and +24V, just right after the

    supply

    connector...

     

    Nice work ....

     

    Ah ok hehe, I've added the 10uF capasitor now.

     

     

    Quote:

    I think there should be a ground connection for each channel. In other

    words, you will need 3-pin instead of 2-pin connectors. Otherwise your

    only ground connection is through the power supply connector. The ground

    pin should be between each input and output pin.

     

    I'm not sure I understand this bit.

    The signal I'm trying to amplify is coming from small oxygen cells

    (galvanic cells). If I understand what you are suggesting, is that I use

    the GND from each cell to connect to their respective inverting input of

    the opamp? My original idea was to tie all the GND lines from the cells

    into the same GND connector (the one I also connect the power supply to).

    Potentially a stupid question.. will that work? I don't need to ground

    everything "together"?

     

    Quote:

    If you swap the ends of R5 and R6, then you can have a single trace for

    OUT3, instead of 2 traces. You can do the same thing for the other

    channels.

     

     

    Cool, that does look better image

     

    Once again thanks for all the help!!

     

    -Jacob

     

    --

    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

     

    Attachments:
    test5-3.zip
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  • kikoun
    kikoun over 9 years ago in reply to jacob-t

    Hi,

     

    The sensor cell will produce a voltage, between the 2 signals :

    - the signal you will connect to your amplifier input

    - and the GND.

    Only the voltage between these 2 signals (the difference) is important. The current that will flow out from your cell into the input of the amplifier is exactly the same than the current flowing from the GND of your board into the GND pin of your cell.

    So, the role played  by the 2 wires of the oxygen cell (signal and GND)  is equivalent, and there is no reason to have a different path (except if GND is also used to supply the sensor see (*) ).

     

    On the amplifier side : it amplifies the difference between the input signal and the GND plane, the GND plane is a REFERENCE.

     

    If instead of connecting directly the GND of sensor to your board, you connect it to a point away from the plane (name it STAR point), with all the other sensor GND and supply GND, then you connect this start point to your board with a single wire. On the paper this will work.... but....

    In this last GND segment (wire from the GND plane and star point)  you will have the sum of all the currents of all sensors, plus the current drained by the amplifier it self (and this last one is far more important than the others).

    Where is the problem ?

    The problem is that the copper is a good conductor, but not an ideal one !

    You will have a little voltage difference between your GND plane and the start point, that will be dependent of that current, and the length of the wire, and so amplifier REFERENCE will not be exactly the reference of the sensor.

     

    In other word, each signal will be polluted with the signal of the other cell and the consumption of the amplifier...

     

    There is also other advantages of using same path for your sensor: you can use twisted pair wire, that way you reduce noise, specially if your sensor are far away from the borad.

     

    Just one thing (*) : I don't know your sensor: is this sensor need a supply ? How this supply is wired? is the GND of sensor is only a output reference or also used for the return path of the supply ? because in that case you have to figure how best can the GND be wired.... there is no magic solution, and we can help you unless you give us more info...

     

    Sorry with this very quick fast ultra simplified explanation... and if you want to have more fun... you can also question yourself about the output of your amplifier : How the GND path mcan be optimised and wired, on the output side (I suppose you will connect it to an acquisition device...)

     

    Guillaume

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