Help reading schematic

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  1. - 1st October 2010, 03:04 #1
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    Default Help reading schematic


    I'm having a little trouble reading this schematic mostly with the FDC6420C mosfets. I know there are only 4 (says in parts required) and are 6 pin. I just don't know which ones get paired up. I'm used to more of automotive wiring diagrams.

    Also on the BAT54S diodes, are these 3 pin? If so would someone have a full part number as I already have 2 pin ones.

    Thanks
  2. - 1st October 2010, 08:45 #2
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    Welcome to the forum.

    http://www.fairchildsemi.com/ds/FD/FDC6420C.pdf
    http://www.fairchildsemi.com/ds/BA/BAT54.pdf

    The FETs are paired N and P. The diodes are three pins. The data sheets show all of that.

    Automotive type???
    Dave
    Always wear safety glasses while programming.
  3. - 1st October 2010, 09:00 #3
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    Quote Originally Posted by mackrackit View Post
    Automotive type???
    Hi, Dave

    Automotive type electrical SCHEMES ...

    sure they're somewhat different ...

    Alain
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  4. - 1st October 2010, 21:05 #4
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    Also on the BAT54S diodes, are these 3 pin? If so would someone have a full part number as I already have 2 pin ones.
    Any schottky diode of 500 mA 30 volts will be ok as a replacement.

    Every FDC6420C should be regarded as half bridge. It incorporate both the N & P channels mosfet.

    The circuit function is a driver for a bi-polar stepper motor with 12 volts @ 2 Amps max per winding.

    Cheers

    Al.
    Last edited by aratti; - 1st October 2010 at 21:10.
    All progress began with an idea
  5. - 2nd October 2010, 01:45 #5
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    As an automotive service technician, just more used to their type of wiring diagrams. They just don't show a single component in two parts. Mostly just a box or dotted line around it to show you which module your looking at.

    For the mosfets I'm just not sure which gets paired up. For example does Q3:A go with Q5:B or is it Q6:B?

    I'm beginning to wonder if I accidentally got the wrong diodes shipped to me. I ordered BAT54SCT-ND SOT23-3 from Digikey and got a two pin diode with 2002 written on top.

    I'm reconstructing an instrument cluster to fit into my classic truck cause aftermarket metric guages are almost non existant and I want all 6 guages. I'm going to be using Fraen AMD 6405-1512 stepper motors (5v 22ma).
  6. - 2nd October 2010, 01:58 #6
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    An "A" gets paired with a "B" or N with a P.
    Sounds like they may have shipped the wrong diode. SOT23-3 with two pins?
    Dave
    Always wear safety glasses while programming.
  7. - 2nd October 2010, 02:36 #7
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    Quote Originally Posted by 51dueller View Post
    I'm going to be using Fraen AMD 6405-1512 stepper motors (5v 22ma).
    I'm not sure how far down this road you are, but this circuit is way bigger then you need for this motor. Now of course it should work, but there are smaller simpler solutions if you are intrested.
    -Bert

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  8. - 2nd October 2010, 10:21 #8
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    Quote Originally Posted by 51dueller View Post
    As an automotive service technician,
    ...
    I'm reconstructing an instrument cluster to fit into my classic truck cause aftermarket metric guages are almost non existant and I want all 6 guages. I'm going to be using Fraen AMD 6405-1512 stepper motors (5v 22ma).
    Hi, 51

    a look here ???

    http://www.sportdevices.com/ignition/tacho.htm

    Ok, not bipolar stepper ... but minor mod.



    Alain
    Last edited by Acetronics2; - 2nd October 2010 at 10:25.
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    certainly the answer is " RTFM " or " RTFDataSheet " !!!
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  9. - 2nd October 2010, 01:53 #9
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    Wow, have to thank all of you. I bet I have read that app note 3 or 4 times in the past. Problem was, when I read it I wasn't looking for a bi-polar drive. Now for the past 5 months I have been putting together a 6 axis drive for 2A bi-polar/uni-polar steppers. I settled on a uni drive for convineance and price. This is a worthwhile drive circuit, deserving much deeper look.

    So far, it looks to be both cost effective and manufacturable!

    So again, thanks! Now as I develop this further, should I start a new thread or continue this one?
    -Bert

    The glass is not half full or half empty, Its twice as big as needed for the job!

    http://foamcasualty.com/ - Warbird R/C scratch building with foam!
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