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Thread: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

  1. #25
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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Good to hear from you again kb0nly but sorry to see you have had bother with your computer. The circuit and board layout diagrams are below...


    CNC 3020T-DJ Spindle Control, JP-382A JP-1482-capture-2-jpg CNC 3020T-DJ Spindle Control, JP-382A JP-1482-capture-1-jpg

    The circuit board was milled (of course) and I could provide g-code files if you wish.

    The HEX file is attached. A word about the software if I may. It's functional, but should be treated as a beta release. The original source code is written in the excellent Proton BASIC language. If you want the source let me know. It's fairly simple and should easily translate into other BASICS or the likes of C.

    A word or two about the software if I may. About 10 times a second the software measures the period that a single PWM cycle is at logic zero and produces a number typically between 6 and 245. At low RPMs this number is high, and at high RPMs low. The number is then averaged over 4 PWM cycles to reduce the chance of ‘flickering’ between consecutive readings.

    The next stage is to take the PWM number and convert it in such a way that it can be used to control a digital rheostat. In effect the analogue pot on the front panel is being replaced by a digital one. This is not a simple task. For starters, the spindle does not start to rotate until the resistance has been reduced from about 5k to approximately 3.8k. Consequently an offset must be applied to the number fed to the rheostat chip. The second problem is that whilst the numbers produced by the Mach3 software are beautifully linear, the behaviour of the spindle motor is most definitely not. This means that the software not only has to take care of the offset problem, but it must scale the PWM number to correct for the non-linear nature of the Spindle motor before it is transmitted to the rheostat. This it does well, however there are some interesting issues that make life difficult.

    The software aims to spin the motor at a speed (in RPM) near that indicated in the Mach3 software. It is never likely to be an exact match. This is because the spindle speed varies with AC mains voltage in a significant way. The DC supply is not stabilised and there is nothing that can be done about this unless a different, stabilised, power supply is used. A second problem is that the controller has no feedback mechanism which allows the actual spindle speed to be monitored. This means that the software has no method of correcting for motor loading. I’ve tried to compensate for this by having the spindle rotate at a faster rate off load. So, for example, if Mach3 is set at 8000 RPM, then it is likely that the off load spindle speed will be in excess of 9000 RPM. Again the actual speed will depend on the AC mains voltage at the time. All of this said, I’m pretty certain that these problems exist on all the PWM controllers at the budget end of the market.

    If this wasn’t enough, the JP-1482 controller has a couple of interesting features. As I have mentioned in a previous post, the speed at which the spindle rotates is not just dependent on the position of the control knob on the front panel. It can also depend on the previous position of the knob! Try marking a position on the spindle control knob scale about 2/3 of the way along. Start from the minimum setting and rotate the knob to the marked position. Note the spindle speed. Next rotate the knob until you get maximum speed and then move it back to your marked point. Measure the speed once more. You'll find there is a several thousand RPM difference! To overcome this problem, the software looks to see if the user wants to increase or decrease the spindle speed. If the spindle speed is being decreased, then the resistance of the rheostat is set to maximum for a period of 25ms before returning to its correct setting. This makes the JP-1482 controller ‘think’ that the control knob is being rotated from the minimum position. Normally the user will not notice this.

    The second issue is that, although it appears as if rotating the spindle control knob gives a smooth increase or decrease in speed, I’m not certain that this is the case. I suspect that changes in speed, especially at lower RPMs, are incremental. The practical consequence of this is that occasionally, with small speed adjustments, changing the speed in MACH3 does not produce a change in spindle speed. The software is changing the resistance of the rheostat, of that I’m certain. Further investigation is needed.

    MACH3 SETTINGS

    The software is built around some specific settings and are the ones recommended in the controller documentation. These are:

    Kernel Speed: 35000Hz (Do not change.)
    PWM frequency: 200Hz (Do not change.)
    Minimum PWM 10%
    Maximum pulley speed: 11000 rpm (Don’t set a minimum.)

    Please note that the software has a minimum speed of around 2000 RPM.

    I’ll probably spend some time developing this board and software for myself. If I manage to make significant improvements, I’ll post them here. If anyone comes up with a better method of controlling the JP-1482 I hope they’ll do likewise.

    In the mean time if anyone else does try to build this, I’d be interesting in hearing how you get along.

    As always, make sure you know what you are doing around mains voltages. All modifications to your controller are entirely at your own risk.



    Bob

    Attached Files Attached Files
    Last edited by Mellbreak; 01-08-2015 at 03:11 PM. Reason: Additional information added.


  2. #26
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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Post removed by Mellbreak.



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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    New information added to post 25.

    Bob



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    Quote Originally Posted by kb0nly View Post
    Ok, i got tired of having to flip the Spindle switch all the time and decided it was time to get Mach3 doing its job!

    I have a newer version of the Chinese CNC 3020T-DJ with a black controller box and the controller board is model JP-382A and the spindle board is JP-1482.

    The controller has a PWM output and the spindle board has a PWM input but they are not connected. Here is some pictures i included on another post..


    After i got done adding home switches to the controller i also started to trace out the boards to figure out the Spindle control.
    I just received my 3020T-DJ with the same controller box and powered it on for the first time. It looks like Mach3 is working correctly and I will be modifying the spindle on/off like you have described. Can you fill me in on adding the home switches? More specifically, how to do it and what do I need to add them? I plan on using this for engraving small plastic parts and wood. (kb0nly, it seems we may have gotten licensed the same year. I had a vanity license for a while and then went back to my original call sign)



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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    how are you measuring the spindle speed?

    sorry to resurrect a dead thread. I just got this machine.

    best P



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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Hi Canislupus,

    At the moment, although I'm looking into this, there is no direct method of measuring spindle speed. In this case the board I built measures Mach3's PWM signal and adjusts the spindle motor speed accordingly. It's an imperfect solution, but so far nobody seems to have come up with a better method of providing software control with the JP-382A and JP-1482 boards. In practice it all seems to work well enough.

    Regards,

    Bob



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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Do you think Id be able to implement your solution after changing the JP-382A to an Arduino Uno and a GRBL shield? is basically what im doing. the thing is, as of right now, I can isolate the two boards, in other words the arduino and steppers will be powered via the USB and this doesn't have to attach to the spindle chip at all. I checked this out by isolating the JP-1482 from the JP-382A and the spindle still works fine. Im not super familiar with electronics (I started this project to get some experience) but i think that the arduino has PWM stuff. Also, I plan to use universal g code uploader or something similar to run the steppers, so I really do have a lot of work ahead of me. Do you have any general tips? I can start a new thread and update it with progress if that would be more appropriate.

    Thanks!

    best P



  8. #32
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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Quote Originally Posted by kb0cyl View Post
    I just received my 3020T-DJ with the same controller box and powered it on for the first time. It looks like Mach3 is working correctly and I will be modifying the spindle on/off like you have described. Can you fill me in on adding the home switches? More specifically, how to do it and what do I need to add them? I plan on using this for engraving small plastic parts and wood. (kb0nly, it seems we may have gotten licensed the same year. I had a vanity license for a while and then went back to my original call sign)
    I just saw posts to this thread in my email again while cleaning out my inbox, so sorry for the extremely long delay in getting back here, its been a crazy year with all the work i have taken on in my little shop.

    The limit switches are just basic micro switches that i added with some brackets i made up, nothing fancy. I can get some pictures of it if you wanted to see it. The way i set them up in Mach3 though is to use them as homing switches, So i can home all axis before a project. As for what you would need to add them, its just a few basic things, JST connector as mentioned back a page in this thread, then i used the same style microphone plug and panel mount jack to mount it up in the back panel. The wiring was what took the longest as i took the cable chains apart and routed the switch wiring with the existing wiring to make it all neat.

    I will have to get some pictures as it would far better explain what i did for them. Unless your worried about crashing it to a limit i wouldn't honestly bother with it, i thought it would be nice to have the homing switches but in the end i generally just zero the axis to the work i clamped down and hardly use the homing feature anymore. But then thats because 99% of the work i do on this machine is making PCB's, and i make an acrylic table thats bolted to the aluminum table with insets routed out for different size PCB blanks. So i just toss in a blank tape the corners down and then zero the engraving bit to the corner and away we go.



  9. #33
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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Quote Originally Posted by canislupus View Post
    Do you think Id be able to implement your solution after changing the JP-382A to an Arduino Uno and a GRBL shield? is basically what im doing. the thing is, as of right now, I can isolate the two boards, in other words the arduino and steppers will be powered via the USB and this doesn't have to attach to the spindle chip at all. I checked this out by isolating the JP-1482 from the JP-382A and the spindle still works fine. Im not super familiar with electronics (I started this project to get some experience) but i think that the arduino has PWM stuff. Also, I plan to use universal g code uploader or something similar to run the steppers, so I really do have a lot of work ahead of me. Do you have any general tips? I can start a new thread and update it with progress if that would be more appropriate.

    Thanks!

    best P
    Sounds like you really took on a job there! I wouldnt know where to begin suggesting on that! I have very little Arduino experience. But i suspect as long as the Arduino can toggle the on and off like the original controller did there is no reason it couldn't. All it would take is an analog output from the Arduino to switch it.



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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Hi All,

    Received my 3040 CNC with 800W VFD Motor few days ago. I Got X,Y,Z communication with Mach 3 software to work.

    Bad New: Mach 3 software is not able to turn on/off the spindle or control it. Or even give me a read out on the RPM.
    So far I can only control it manually from the inverter. The inverter gives me a Frequency Digital Display (Hz readout though that I can convert to RPM)

    Is there an easy fix to this (pin- port config) with out having to make hardware changes?

    My controller should be TB6560, but logo on controller says JD.. or HNE something something, see picture below

    CNC 3020T-DJ Spindle Control, JP-382A JP-1482-img_4690-jpg

    Thank you,
    Rob



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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    kbOnly,

    I have found another way of turning the Spindle on and off without hacking the JP-382A at all.

    This is obviously if you have the low voltage issue, and do not intend on using the A Axis.

    I connected 5V pin from A Axis to Pin 4 of the Speed controller (4th from the left when looking from the front), then The PU (Pulse) pin from A Axis to Pin 3 of the Speed controller. I then placed a 1kOhm resistor between the two wires.

    I intend going an alternate route with my PWM speed control. I tried using the A Axis Direction Pin directly in place of the Potentiometer. As the Pot simply pulls a MCU pin to ground to speed up the Spindle it is limited to 5 V. Using A Axis output you have direct access to the Parallel port pins. Keep in mind there is no optical isolation. The Parallel port can not pull enough current to ground to slow the spindle to a crawl and only gives you speed control from around 70%-100%.

    I am going to build a small PWM switching signal through a Opto and Filtering (Maybe RC filter) that will essentially replace the POT.

    What are your thoughts.

    Great job on your mods, just trying to develop a simpler method.



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    Default Re: CNC 3020T-DJ Spindle Control, JP-382A JP-1482

    Quote Originally Posted by Mellbreak View Post
    Hi Canislupus,

    At the moment, although I'm looking into this, there is no direct method of measuring spindle speed. In this case the board I built measures Mach3's PWM signal and adjusts the spindle motor speed accordingly. It's an imperfect solution, but so far nobody seems to have come up with a better method of providing software control with the JP-382A and JP-1482 boards. In practice it all seems to work well enough.

    Regards,

    Bob
    I know this is an old thread, but have just got the controller (ha, the E-Stop button was loose- the flimsy plastic threaded piece had bust). Can't find much info about these boards, except for here. The 3020 user manual stated turning up the rheostat too quickly risks burning out the board, at best just blowing a fuse. Thing is, the photos in the manual were of the old style (blue) controllers so maybe it was just a problem with those. These do seem reasonably well built I think.

    Anyway, would it be possible to use the stepper board feedback signal to determine loading? It measures current through the 0.2R, which will be effected by spindle load.

    Has anyone tried changing logic on the unused mcu pins and see if that has an effect on the manual/auto pwm operation? Would think that the controllers that have software control, would also have a manual alternative.



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