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  1. #1
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    775 dc motor 18v

    i bought a 775 18v dc motor for my cheap cnc 3018 from here
    https://gimsonrobotics.co.uk/categor...motor-775-type

    the reason i bought it was because the Chinese version seemed a little slow running off 24v (did the job but wanted more speed)

    now when i put this new 775 motor in it just pulsates like its just revving every 1-2 seconds, i have a hunch its because its drawing the power from the control board so could someone check the specifications on the above link and advise me on what size/type of power supply i need or any further help would be very much appreciated.

    this is the machine i have
    Attached Thumbnails Attached Thumbnails cnc 3018.jpg  

  2. #2
    Community Moderator Al_The_Man's Avatar
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    Re: 775 dc motor 18v

    Try a test using a 12v automotive battery and see if it performs OK?
    Some of those spec's seem rather suspect to me, I don't see it passing 50+ amps at max power!!?
    103 amps at stall??
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

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    Re: 775 dc motor 18v

    thank you very much al i will check it out and report back

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    Re: 775 dc motor 18v

    Looks like it requires 16 Amps at maximum efficiency. Specs says if a 215W motor. Seems about right.
    Don't know about the stall current. No power supply could supply that much anyway.....Must be 'theoretical'.

    It draws 2A at no load.
    What is your Power Supply maximum current? You would probably want one with a max current of around 20A to be safe.

    Click image for larger version. 

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    Re: 775 dc motor 18v

    power supply i have is 3amp 24v dc output which came with the machine along with another power supply that is 12v dc output, both power supplies plug into the controller and the Arduino is powered by 5v via the usb cable. so i have a hunch this new motor will need an independent power supply. how the hell I'm gonna find one though is beyond me. the machine works fantastic for basic engraving and the probe i made for it also works great. What i want to do with this machine is put a more powerful motor in it with a er11 chuck so i can do 3d carving with it and then after that is hopefully achieved i will be buying some new extruded aluminium and some lead screw rod and round plain bar to make this machine bigger. also does anyone have a recommendation for buying decent 1/8 bits preferably from the UK as i only have two 20 degree V bits which came with it.

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    Re: 775 dc motor 18v

    tested on my car 12v battery and works ok so its looking like i need to find a separate power supply for this as per Sterob's reply as well.

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    Re: 775 dc motor 18v

    Ok...sounds good.
    I'm not familiar with your setup, but it sounds like you definitely need a high current PS for your new motor.
    How is it switch on and off? A relay?. Better check he ratings on that as well. I assume its only rated low for the original motor.

  8. #8
    Community Moderator Al_The_Man's Avatar
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    Re: 775 dc motor 18v

    Do you have a controller or is it switched direct, For a P.S. it is preferable to go with a linear supply if possible, these are far more rugged than a SMPS (switching) and simpler to fix, a simple suitable 20a secondary transformer and a bridge is all that is needed.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  9. #9
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    Re: 775 dc motor 18v

    control board is here Al in this other post about the controller which i have since figured out

    http://www.cnczone.com/forums/chines...706-forum.html

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    Re: 775 dc motor 18v

    Is this your Router?

    DIY CNC 3 Axis Engraver Machine PCB Milling Wood Carving Router Kit Arduino Grbl - LinkSprite Playgound

    If so, then I think maybe you are trying to get the machine to perform way higher than it was designed to do and you may stumble upon problem after problem, in your quest.
    Just something to be aware of. I hope this is not the case for you.

    Motor appears to get its power via the control board? I assume this means its a PWM signal to enable speed control of the motor.....You may have to find a way to get a speed signal from your board to another high power speed controller and use a external 24v DC power supply to power the motor.
    You will have to do reach on the board to see if there is such an output you can use.
    See how it gets messy pretty quick?

    I'm speculating so I may wrong with all this...just thinking out loud.

    Steve

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    Re: 775 dc motor 18v

    Is this same board as you have? Current is limited to 10A.
    Click image for larger version. 

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    Re: 775 dc motor 18v

    not identical but practically the same yes, so i don't mind going down the route of utilising a separate power supply just for the new motor but i have not got a clue what parts to buy or where to buy them from, i can build a cnc machine and i have built a full digital twin infrared reflow station but when it comes to a power supply to run this little motor its beyond me. i also have a cheap 35000 rpm dremel type machine but the diameter of it is 52mm and i didn't really want to start refabricating/modifying the mount on this machine to accommodate it as i wanted to be able to still use the original crappy motor in it that is to a degree useful for plastic/acrylic. so basically i am in a predicament and at all of your mercy for your advise on how to go about this. i don't usually need to be spoon fed on issues like this but on this occasion i think i need to be.

    thanks again to everyone who is advising me the best they can i really do appreciate it.

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    Re: 775 dc motor 18v

    this is the same steve yes only difference is mine is the bigger frame/table model (3018) which basically means 300mm x 180mm working area.

    Quote Originally Posted by Sterob View Post
    Is this your Router?

    DIY CNC 3 Axis Engraver Machine PCB Milling Wood Carving Router Kit Arduino Grbl - LinkSprite Playgound

    If so, then I think maybe you are trying to get the machine to perform way higher than it was designed to do and you may stumble upon problem after problem, in your quest.
    Just something to be aware of. I hope this is not the case for you.

    Motor appears to get its power via the control board? I assume this means its a PWM signal to enable speed control of the motor.....You may have to find a way to get a speed signal from your board to another high power speed controller and use a external 24v DC power supply to power the motor.
    You will have to do reach on the board to see if there is such an output you can use.
    See how it gets messy pretty quick?

    I'm speculating so I may wrong with all this...just thinking out loud.

    Steve

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    Re: 775 dc motor 18v

    I guess Ebay is as good as place as any.
    Maybe something this one?

    https://www.ebay.co.uk/itm/FARNELL-N....c100005.m1851

    Not sure what the Max current output is. It has to be HIGHER than what you need, ie ~15 Amps.
    Research it or ask the seller what its rating is.

    Other than that you could get a Switch Mode Power Supply cheap of Ebay. They are cheap, small, efficient but alot more complicated. Some have to have a load connected before they will turn on......

    A 24V battery charger will work if it can supply enough current.

    A local second hand shop or junk yard may have something?

    Radiospares or Farrnel ( They won't be cheap....lol)


    If you go this route, you will only have FULL SPEED unless to also use a PWM DC Motor Speed Control. ( cheap on Ebay ) and you wil ahve to turn the spindle on and adjust the speed manually...not a big deal....



    There's a few options.

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    Re: 775 dc motor 18v

    thanks for the suggestions I'm not too bothered if the motor is running at full speed, and was wondering if you could tell me if this could be used on the link below

    https://www.ebay.co.uk/itm/DC-5V-12V...-/162562112782

    thanks again

  16. #16
    Community Moderator Al_The_Man's Avatar
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    Re: 775 dc motor 18v

    Personally I would rather pay a little more and get a linear supply, especially for motor/stepper use. they are far more rugged and easier to fix, Should they go wrong.
    Also easy to put one together with a very few components.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

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    Re: 775 dc motor 18v

    Quote Originally Posted by newbie_cnc3018 View Post
    thanks for the suggestions I'm not too bothered if the motor is running at full speed, and was wondering if you could tell me if this could be used on the link below

    https://www.ebay.co.uk/itm/DC-5V-12V...-/162562112782

    thanks again
    *Maybe*.....Its a bit of a crap shoot. I may have misled you regarding SMPS's. I can't say for sure without a benchtest and that would not be easy to arrange.
    See:
    https://www.power-supplies-australia...-use-dc-motors

    I agree with Al.....a simple linear power supply would be the best solution. Any simple DC power supply would be less of a risk than a complicated Switch Mode PS. Rugged and easy to fix.

    Steve

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    Re: 775 dc motor 18v

    I just saw this:

    https://www.youtube.com/watch?v=B7gHeJo5rjQ

    It appears to work ok. Current rating is too low for you though....

    Steve

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    Re: 775 dc motor 18v

    thanks steve i am going to mount my variable speed 240v 35000 rpm dremel look alike rotary tool as i did a mock test with it and wow what a difference it made, cuts were so clean and increasing the feed rate is remarkable. so for now i'll put this dc motor on the back burner but thank you so much for your help.

    Quote Originally Posted by Sterob View Post
    I just saw this:

    https://www.youtube.com/watch?v=B7gHeJo5rjQ

    It appears to work ok. Current rating is too low for you though....

    Steve

  20. #20
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    Re: 775 dc motor 18v

    If you Dremel type machine does not cut it....Maybe this would suit.

    Mini engraving motor 300W + Switching power supply 48V 350W - CNCdrive - webshop

    It might fit straight in...it look similar.
    Steve

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