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IndustryArena Forum > CNC Electronics > CNC Machine Related Electronics > Reversed Logic voltage to PICSTEP- What component to be replaced?
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  1. #1
    Join Date
    Jul 2008
    Posts
    390

    Driver Chip Test

    Khalid,

    This is likely to be the first of many posts. I am going to try to diagnose the issues little by little, so I will need you to try certain circuit configurations with the parts you have, and maybe others.

    Disclaimer: Please understand that I am neither responsible nor liable for any actions or harm caused...

    The first thing you need to do is get rid of the 33pf capacitors for the crystal. Those will NOT work with the PIC you are trying to use.:nono: With a 20MHz Crystal (classified as HS), you MUST use 15-30pF capacitors. I recommend a capacitor in the middle of that range, such as 20pf.

    Lets start with the most basic electronic components and move up to the most difficult.

    The second thing I think you should do is mess with the driver section of the circuit. It is worrying that you can't get the motor to engage at all...
    So here is what I want you to do: Remove the PIC from the IC socket. Using quite a few jumper wires, construct the attached schematic by putting wires into the corresponding slots in the PIC IC slots. For instance, you should connect a +5v wire to pins 4,6,7,8 of the PIC IC socket, where the IC used to be, etc. Do all of that except for the direction pin. Now, with all the wires connected as I have laid them out in the schematic, spin the motor. It should still move freely. Now attach the direction pin marked as a red switch in the schematic, (RB6, pin 12 on the IC socket) to the +5V source. The motor should now lock or resist you turning it.

    Remember to disconnect resistor R9 in the original schematic.

    If that test is successful, that means that the problem is likely with the PIC or a wire mishap.
    If the test was unsuccessful, your driver chips may be blown, bad stepper, bad driver wiring, or I may have read the datasheet wrong.

    Also, please attach a picture (or two please) of the underside of the board.


    Other Questions:
    1. Do you have spare LEDs and 100 - 200 ohm resistors?
    2. Have you completed the LED Flasher project you talked about in post #29? It would be good if you did.
    3. You do have an ohm meter, correct?
    4. What is the amperage ratings on your +5V and +24V supplies?


    Well it is very late now... I will post again tomorrow after you have tried the above.
    Attached Thumbnails Attached Thumbnails LMD18245 circuit.png  

  2. #2
    Join Date
    Apr 2006
    Posts
    3498
    Quote Originally Posted by amishx64 View Post
    Khalid,

    This is likely to be the first of many posts. I am going to try to diagnose the issues little by little, so I will need you to try certain circuit configurations with the parts you have, and maybe others.

    Disclaimer: Please understand that I am neither responsible nor liable for any actions or harm caused...

    The first thing you need to do is get rid of the 33pf capacitors for the crystal. Those will NOT work with the PIC you are trying to use.:nono: With a 20MHz Crystal (classified as HS), you MUST use 15-30pF capacitors. I recommend a capacitor in the middle of that range, such as 20pf.

    Lets start with the most basic electronic components and move up to the most difficult.

    The second thing I think you should do is mess with the driver section of the circuit. It is worrying that you can't get the motor to engage at all...
    So here is what I want you to do: Remove the PIC from the IC socket. Using quite a few jumper wires, construct the attached schematic by putting wires into the corresponding slots in the PIC IC slots. For instance, you should connect a +5v wire to pins 4,6,7,8 of the PIC IC socket, where the IC used to be, etc. Do all of that except for the direction pin. Now, with all the wires connected as I have laid them out in the schematic, spin the motor. It should still move freely. Now attach the direction pin marked as a red switch in the schematic, (RB6, pin 12 on the IC socket) to the +5V source. The motor should now lock or resist you turning it.

    Remember to disconnect resistor R9 in the original schematic.

    If that test is successful, that means that the problem is likely with the PIC or a wire mishap.
    If the test was unsuccessful, your driver chips may be blown, bad stepper, bad driver wiring, or I may have read the datasheet wrong.

    Also, please attach a picture (or two please) of the underside of the board.


    Other Questions:
    1. Do you have spare LEDs and 100 - 200 ohm resistors?
    2. Have you completed the LED Flasher project you talked about in post #29? It would be good if you did.
    3. You do have an ohm meter, correct?
    4. What is the amperage ratings on your +5V and +24V supplies?


    Well it is very late now... I will post again tomorrow after you have tried the above.
    Thank you for the detailed reply and procedure. I have some comments:
    1- I have used 33PF then 27PF and now using 12PF with no good response.
    2- Currently 15PF are installed across the 20MHz xtal.

    I have some questions for you regarding the circuit:

    1- Are you talking placing jumpers in PIC IC socket or the LMD??? As your attached schematic shows LMD Pin Out..
    2- Is it possible if you can mark on the attached picture where i installed jumper and what Resistor i remove..

    Point wise Answers for your Questions:
    1- yes I have LEDS and 100, 220ohm resistors.
    2-No i didn't ..
    3- yes I have Multimeter that includes Ohmmeter...
    4- +5V supply is ATX power supply and it has more than 6 Amp. where as +24V supply has 3 Amp.. I am using 1.2 Amp motor.(single Motor)


    PS:
    Frankly speaking i am fed up with this PICSTEP.. I have assembled the three boards and no-one work
    Attached Thumbnails Attached Thumbnails picstep_v4_0_overlay.jpg  
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/

  3. #3
    Join Date
    Jul 2008
    Posts
    390

    PIC Socket Connections

    Quote Originally Posted by Khalid View Post
    Thank you for the detailed reply and procedure. I have some comments:
    1- I have used 33PF then 27PF and now using 12PF with no good response.
    2- Currently 15PF are installed across the 20MHz xtal.
    Yes, 15pf is good. Continue using those. Don't waste your time with the others.
    Quote Originally Posted by Khalid View Post
    I have some questions for you regarding the circuit:

    1- Are you talking placing jumpers in PIC IC socket or the LMD??? As your attached schematic shows LMD Pin Out..
    2- Is it possible if you can mark on the attached picture where i installed jumper and what Resistor i remove..
    1. Answers:
    2. Jumpers go into the PIC IC socket where the PIC used to be. Since you have 'supposedly' correctly connected the PIC IC socket to the LMD driver, this will be a good test of those existing connectioons. You will not put jumpers into every pin of the PIC IC socket.
    3. Sure. Give me two pictures then: A close up of the IC socket with the surrounding components visible (~20mm away from the edges) and one near the LMD drivers. I will Photoshop the connections in for you.


    Also, please attach a picture of the underside of the board as I asked in the last post when you can.

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