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    Default Re: DIY AC Servo Drive - ATMega based

    Here is the latest schematic and firmware. I've reached V1.4.
    The PCB is slightly changed as we have some new resistors, (some big in size, must be at least 5W) and some other minor parts.

    I am really waiting for someone else to build this.

    Mihai

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    Default Re: DIY AC Servo Drive - ATMega based

    Nice work! Sorry to ask again, but could you post a schematic in pdf, png, jpg, something we don't need Eagle to read? And you wouldn't happen to have a BOM?

    I'm holding off at this point simply because of the parts cost, but perhaps the cost could be lower with other components that would also work? E.g. those fets are spendy and add up fast x6. As you noted, the smaller AVR's cost about the same, but there are other uC's like stm32f103 that are far cheaper and faster, etc.. Don't be afraid of SMT soldering, it's really no where near as hard as people think, I teach a class in soldering from this presentation, and slide 18 and 19 (after learning to solder in the prior slides) along with the video are all most people need to solder fine pitch with regular equipment.

    https://docs.google.com/presentation...g470e74144_041



    If the parts cost can be reduced, I'd be willing to seriously consider making a kit available with a professionally made PCB.

    James hosts the single best wiki page about motors for CNC hobbyists on the net:
    http://techref.massmind.org/techref/io/motors.htm Disagree? Tell him what's missing! ,o)


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    Quote Originally Posted by James Newton View Post
    Nice work! Sorry to ask again, but could you post a schematic in pdf, png, jpg, something we don't need Eagle to read? And you wouldn't happen to have a BOM?

    I'm holding off at this point simply because of the parts cost, but perhaps the cost could be lower with other components that would also work? E.g. those fets are spendy and add up fast x6. As you noted, the smaller AVR's cost about the same, but there are other uC's like stm32f103 that are far cheaper and faster, etc.. Don't be afraid of SMT soldering, it's really no where near as hard as people think, I teach a class in soldering from this presentation, and slide 18 and 19 (after learning to solder in the prior slides) along with the video are all most people need to solder fine pitch with regular equipment.

    https://docs.google.com/presentation...g470e74144_041



    If the parts cost can be reduced, I'd be willing to seriously consider making a kit available with a professionally made PCB.
    Thanks for the interest. It's late now for me but I will post a Pdf or something tomorow. I used some other mosfets with success in pair with the ir2101 drives. The irfz44 work ok and are about 2 $ for 6 pieces. Some other mcu's can be used for sure. Like the Atmega64 or Atmega128 (smds). Basically what I have on 1 board costs about 30$, including radiator. But I am sure the costs can go lower if we optimise.

    I'll send you some schematic tomorow.

    Mihai



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    Default Re: DIY AC Servo Drive - ATMega based

    Here is the schematic as PNG.

    Mihai

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    Default Re: DIY AC Servo Drive - ATMega based

    Quote Originally Posted by James Newton View Post
    Nice work! Sorry to ask again, but could you post a schematic in pdf, png, jpg, something we don't need Eagle to read? And you wouldn't happen to have a BOM?
    Sorry. I do not know what a BOM is... so it's almost sure I do not have one...

    Mihai



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    Default Re: DIY AC Servo Drive - ATMega based

    BOM is Bill of Materials
    Basically just a parts list of all the components.
    Usually made in a spreadsheet that can be read by Digi-Key, Mouser or Newark.
    Makes it easy to order the parts.

    What about getting some boards made?
    I'm willing to have a run made once the design is workable if a few people will commit to buying.
    Not looking for profit, strictly cost plus shipping.



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    Default Re: DIY AC Servo Drive - ATMega based

    Great work!
    You can generate the list of parts from Eagle. Do a googe search for Eagle and BOM.



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    Default Re: DIY AC Servo Drive - ATMega based

    3 more pcbs about to be made. I'm so tired... The layout has changed a little allowing a TO220 power resistor to be mount on the radiator. Will post new pcb tomorow...

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    Default Re: DIY AC Servo Drive - ATMega based

    Here is the Parts list. Unprocessed, directly exported from Eagle.

    Mihai

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    Default Re: DIY AC Servo Drive - ATMega based

    Quote Originally Posted by mcm_xyz View Post
    Here is the Parts list. Unprocessed, directly exported from Eagle.

    Mihai
    I'm really curious where you buy your parts, 'cause I'm over 40 with only the main components. Check out the BOM on Mouser:
    https://www.mouser.com/ProjectManage...sID=5e17007e20
    and tell me where I'm going wrong?

    James hosts the single best wiki page about motors for CNC hobbyists on the net:
    http://techref.massmind.org/techref/io/motors.htm Disagree? Tell him what's missing! ,o)


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    Default Re: DIY AC Servo Drive - ATMega based

    In Europe they have RS but their prices are as high or higher than Mouser or Digi-key etc..
    Probably got them from China.
    I see 20 for $10 shipped from China.



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    Default Re: DIY AC Servo Drive - ATMega based

    Looking over the schematic.
    I see in SV3. The RS2332 connector.
    In the US we use 2,3 & 5. 2 and 3 being signal and 5 being ground.
    On your schematic you have 6 as ground.

    Is there some reason for this??

    EDIT:
    In the parts list you have:
    C13 0.1u C-EU025-024X044 C025-024X044 rcl 1
    C14 100n C-EU025-024X044 C025-024X044 rcl 1
    I do not find C13 or C14 on the schematic.

    Last edited by jdholbrook; 01-19-2015 at 11:16 PM.


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    Default Re: DIY AC Servo Drive - ATMega based

    Hello again!

    Sorry for the inconsistencies. I did not post the last schematic. Here is the right one. There is a new library including the TO220 Power resistance.
    In the archive you can find: Eagle, PNG files with schematic and board, PartList

    The reason for the 6 pin RS232 connector is that it DOES NOT CONNECT TO COMPUTER DIRECTLY.
    U need a part like this: TTL-232R-5V FTDI - Modul: cu cablu, integrat | TME - Componente electronice
    The pinout work exactly with this cable. It is needed to make the TTL conversion for the signals, and I did not wanted to add more electronics to the board.

    I think the main difference in price are THE CONNECTORS. I am very sure that I did not used the ones that are in the schematic but some other more cheaper...
    The Transistors used by me are IRFZ44E way cheaper.
    A new expensive addition is the TO220 POWER RESISTOR but U can use cheaper resistors if you do not want to mount them so nicely on the radiator...

    Let me know if there are more problems!

    Mihai

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    Default Re: DIY AC Servo Drive - ATMega based

    Quote Originally Posted by James Newton View Post
    I'm really curious where you buy your parts, 'cause I'm over 40 with only the main components. Check out the BOM on Mouser:
    https://www.mouser.com/ProjectManage...sID=5e17007e20
    and tell me where I'm going wrong?
    Indeed the IRF740 are expensive. If you only need to drive low voltage motors you can replace them by IRFZ44E
    IRFZ44EPBF International Rectifier | Mouser

    Way cheaper!

    Mihai



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    Default Re: DIY AC Servo Drive - ATMega based

    Quote Originally Posted by mcm_xyz View Post
    Indeed the IRF740 are expensive. If you only need to drive low voltage motors you can replace them by IRFZ44E
    IRFZ44EPBF International Rectifier | Mouser
    So that limits one to say a 48 volt drive? Ok... that should be useful still, right?

    With that change, I'm at $30 without the caps, some resistors, and the power supply stuff (which I think is unnecessary... +5 is easy to supply separately)

    What current do R7-R11 need to manage? e.g. can we use 1/8 watt? or networked resistor?

    What voltage rating on caps C1-3? 16volt ok?

    Do you have a part number suggestion for R32? Is this one ok?
    HS50 0R10 5% Arcol | Mouser

    Updated list here if anyone wants to order / help find missing parts / edit, etc...
    https://www.mouser.com/ProjectManage...sID=5e17007e20

    James hosts the single best wiki page about motors for CNC hobbyists on the net:
    http://techref.massmind.org/techref/io/motors.htm Disagree? Tell him what's missing! ,o)


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    Default Re: DIY AC Servo Drive - ATMega based

    Quote Originally Posted by James Newton View Post
    So that limits one to say a 48 volt drive? Ok... that should be useful still, right?

    With that change, I'm at $30 without the caps, some resistors, and the power supply stuff (which I think is unnecessary... +5 is easy to supply separately)

    What current do R7-R11 need to manage? e.g. can we use 1/8 watt? or networked resistor?

    What voltage rating on caps C1-3? 16volt ok?

    Do you have a part number suggestion for R32? Is this one ok?
    HS50 0R10 5% Arcol | Mouser

    Updated list here if anyone wants to order / help find missing parts / edit, etc...
    https://www.mouser.com/ProjectManage...sID=5e17007e20
    R7-R11 can be 1/8W no problem. The command current for the MOSFETS is low.
    C1-C3 must support the voltage supplied for ir2101. If I understood correctly the voltage between VS and VB will be max V supply. Any capacitance value startting at 0.1 microF will do.
    R32 must be at least 5W. With 5W resistor I managed to make some smoke after forcing the motor at higher than 2A current limit. What I will use is:

    PWR221T-30-R100F BOURNS - Rezistor: thick film | TME - Componente electronice

    so I can easily mount this one near the Mosfets on the radiator


    Mihai

    PS. Basically you can use any value for R32 in the range 0.3 - 0.05 ohms. Whatever you can find cheaper. 0.1 Ohms seems a good value as it allows measurements of 50A. (5V max measurable voltage by ATMega)
    0.05 will allow 100A but resolution will be lower. 0.2 allows 25A with better resolution. However do not increase the value too much not to loose too much power on the resistor instead of the motor.

    You must then change the value of the shunt resistor in the software. There is a constant in Constants.mpas



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    Default Re: DIY AC Servo Drive - ATMega based

    3 new boards assembled and tested. Waiting for radiator.

    Mihai

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    Default Re: DIY AC Servo Drive - ATMega based

    hi Mihai, what is version mikropascal for avr you use?



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    Quote Originally Posted by tivoidethuong View Post
    hi Mihai, what is version mikropascal for avr you use?
    Latest available. 6.0. It wont compile it because of size limitation of free version... U have to make something about it...



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    Default Re: DIY AC Servo Drive - ATMega based

    Ok, so now it's at $38 dollars, without the programming connector, power supply stuff, and fuse. (I figure you only program once, and will use a PC power supply)

    https://www.mouser.com/ProjectManage...sID=5e17007e20

    And I used network resistors where I could to keep the parts count under control (which means those would need to be replaced with standard to use with the existing board layout, or a new layout made)

    Before I order the parts, I would REALLY appreciate it if anyone would check it over and make sure there are no errors.

    https://www.mouser.com/ProjectManage...sID=5e17007e20

    James hosts the single best wiki page about motors for CNC hobbyists on the net:
    http://techref.massmind.org/techref/io/motors.htm Disagree? Tell him what's missing! ,o)


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