hobby cnc ez board trouble shooting help

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    Default hobby cnc ez board trouble shooting help

    Hi all

    I seem to be having a problem with my ez board. This all started when i decided to upgrade my router machine. After building my new machine and starting the setup i am getting some kind of power cycle or other problem with the ez board. Everything will run fine for about 5 to 10 min then everything will stop with a loud whine from the steppers. It will then start back up again but it is not running right, before the power cycle i am reading 0.4v off the test points for the driver current after the cycle i am getting 0.3v or less. Also after the cycle I am only reading 3v at the 5v test pad If I turn off the machine power and wait a few min everything will come back normal and start the problem over again.

    My build consists of: Hobbycnc EZ board, 2ea Nema 23-305 and 1ea Nema 23-425 stepper motors operating in unipolar config. I am using belts on the X and Y and a lead screw on my Z. I ran 18awg shielded cable for all motors with an average run of about 12 feet. I am using Linux cnc for control software. I was originally suspecting a power supply problem and have tried two different Mean Well LRS-350-24 supplies and also my original 24v transformer/rectifier/cap power supply, all with the same problems

    Thank you for any help

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    Last edited by rotccapt; 12-24-2017 at 03:20 PM.


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    Default Re: hobby cnc ez board trouble shooting help

    Dear rotccapt,

    Could be a couple of things.

    1) seems we can eliminate the power supply as you tried several (smart move)
    2) there are a couple of FAQs on my website that may give some guidance: No motor movement and Checking Voltages.
    3) Touch the two voltage regulators (U4 and U5) during a 'failure' - are they getting warm/hot? (they should NOT)
    4) confirming you do have a substantial heatsink for the driver chips AND a fan blowing across it?
    5) Has your step/accel rate changed (potentially stepping to fast)?
    6) do the axis motors or axis bind? can you manually move the axis freely by hand throughout their range?
    7) do you have anything connected to the 24V fan connector? (TB 6)
    a) are you taking ANY other voltages off the board (e.g. using the +5V to drive an opto board)
    8) triple-check the stepper wiring:
    a) steppers are wired correctly to the board
    b) all joints, connections and screw terminals are secure
    9) do you have any limit switches wired into TB4? (this on is a reach) - perhaps some spurious noise is causing an issue?
    10) is the board clean? that is, nothing got on/in the board (dirt, dust, metal scraps, who-knows-what)

    Regards, BrianV, HobbyCNC

    WoodWorkerB
    WoodWorkerB.com


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    Default Re: hobby cnc ez board trouble shooting help

    thank you for the reply.



    3) Touch the two voltage regulators (U4 and U5) during a 'failure' - are they getting warm/hot? (they should NOT) doing some inspection i noticed that there are dark circles at the base of the solder joints for U5 on the bottom of the board
    4) confirming you do have a substantial heatsink for the driver chips AND a fan blowing across it? i have a piece of aluminum as a heat sink and have two fans one blowing into the encloser and one blowing out
    5) Has your step/accel rate changed (potentially stepping to fast)? old machine had 3.4 for velocity and 54 acceleration. new machine 14.3 velocity and 56 acceleration
    6) do the axis motors or axis bind? can you manually move the axis freely by hand throughout their range?with power off i can move all axis the full range, with power on hey do not move without the controller moving them
    7) do you have anything connected to the 24V fan connector? (TB 6) only thing i have running off the 24v fan is a 24v to 12v regulator to run my two fans and an external 5v regulator to run a relay board
    a) are you taking ANY other voltages off the board (e.g. using the +5V to drive an opto board) no
    8) triple-check the stepper wiring: all good
    a) steppers are wired correctly to the board all good
    b) all joints, connections and screw terminals are secure a couple of the resistors near U5 look to be a little cold on the top of the board but are good on the bottom of the board
    9) do you have any limit switches wired into TB4? (this on is a reach) - perhaps some spurious noise is causing an issue? i have 3 limit switch loops on pins 10,11,12 estop 13 motor rpm pin 15
    10) is the board clean? that is, nothing got on/in the board (dirt, dust, metal scraps, who-knows-what) looks clean

    thinking back i think this problem was happening before but i did not have anything but the fan running off the 24v output and i had other fans running and did not hear the difference



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    Default Re: hobby cnc ez board trouble shooting help

    Just ran the machine again for about 5 minutes. U5 reached 150 *F. U4 was sitting at around 70*F. I did not duplicate a failure this time but i shut everything down when i read that temp.



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    Default Re: hobby cnc ez board trouble shooting help

    just found the circuit diagram for the Hobby CNC EZ board that I downloaded from cnczone a long while ago

    PDF circuit
    hobby cnc ez board trouble shooting help-hobbycnc-ez-m3-schematic-pdf

    if R4 & R6 set U5 (LM317) to 24V out the the power supply needs to be a minimum of 26V
    as most voltage regulator IC's need the input to be about 2V higher than the output to work correctly

    what was the output voltage of your original linear power supply ??? I guess its about 30 to 40 V depending on the load

    when you used the new 24V power supply its possible U5 did not turn on enough to supply at least 7V to U5 the 5V regulator
    and may have been damaged

    the other possibility is one or more of the SLA7085M stepper driver IC's could of been damaged
    if the output of the 5V regulator (U4) was too low for the SLA7085M's control circuit and there was a loss of control of the current through the output stages

    using your new 24V power supplies
    I would first re test the board with the power supply set to 26 or 27V


    or with the power supply set to 24V
    you should be able to remove U5 the 24V regulator and connect the 24V supply directly to the input of U4 - (the 5V regulator)

    John



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    Default Re: hobby cnc ez board trouble shooting help

    im confident that the stepper ic's are good, i have positive control of all three axis before and after the failure. the only things that is not working after the failure is the 24v fan port and the 5v reading on the test pin. after the failure the 24v connection will only power the led's of my fans



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    Default Re: hobby cnc ez board trouble shooting help

    if you can post high resolution photos of both sides of the board
    it may be possible to trace the connections and compare them with the circuit diagram

    with the additional information it should be possible to work out how to test the PCB board

    John



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    Default Re: hobby cnc ez board trouble shooting help

    here are some pics of the board. i have circled U4 and U5 in the pic of the bottom of the board. the blue wire on the bottom of the board is pin 9 (usually not connected) im using it for spindle control

    Attached Thumbnails Attached Thumbnails hobby cnc ez board trouble shooting help-kimg0203-jpg   hobby cnc ez board trouble shooting help-kimg0202-jpg  


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    Default Re: hobby cnc ez board trouble shooting help

    First off, the fan connector is FOR A FAN ONLY. The regulators on this board are designed to run the board only.
    The MAXIMUM (and I'd be afraid to go there) you can pull from the +24V Fan connector is 300mA (0.3A) without a heatsink. It should not be hot to the touch under normal operation.
    You could try throwing a decent heatsink on the 24V regulator (U5).

    It is best if the fan is blowing onto/across the heatsink, not just circulating air in the enclosure.

    Regarding john-100 suggestions (Thank you john-100!):

    when you used the new 24V power supply its possible U5 did not turn on enough to supply at least 7V to U5 the 5V regulator and may have been damaged
    If the input to U5 (24V regulator) drops below about 27 volts, then the output of U5 will drop with the voltage. It would take a very low input voltage to cause the 5V to not regulate properly.
    Low voltage input will not damage these chips - however over voltage and over current will!

    or with the power supply set to 24V you should be able to remove U5 the 24V regulator and connect the 24V supply directly to the input of U4 - (the 5V regulator)
    Technically a fine suggestion, but I'd rather you run your fans and the relay board off the 24V power supply directly and put nothing on the fan connector.
    If your 24V regulator is indeed blown, let me know. (brian@hobbycnc.com)

    THE MAXIMUM CURRENT you can pull from the fan connector is 300mA (0.3A) without a heatsink. I could not recommend drawing more than this, heatsink or not. This is a 'convenience' connector, not designed for more than a fan.

    24V seems low for one of the motors you have (the 425 oz in)

    BrianV, HobbyCNC

    WoodWorkerB
    WoodWorkerB.com


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    Default Re: hobby cnc ez board trouble shooting help

    woodworkerb, if u5 were to be the culprit would it cause u4 to read low? during the last failure i read 3v at the 5v test pad



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    Default Re: hobby cnc ez board trouble shooting help

    looking at the first photo in post 8

    the 3 soldered joints of the 24V regulator (U5) are discoloured and may of been hot enough to damage it
    or at least cause it to shut down to protect its self , removing the supply to the 5V regulator (U4) for the SLA8085M stepper drivers !

    if the 24V regulator output drops to about 5V
    I would expect the the 5V regulators output to be about 3V

    what are you using as the ground connection for your voltmeter ?

    as its midnight I will study the photos and add more tomorrow

    John

    PS
    Brian its good to know the SLA8085M IC's don't self destruct with the loss of the 5V supply like the infamous TB6560 IC's !!!!!!



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    Default Re: hobby cnc ez board trouble shooting help

    for ground i was using the (-) connection for the power supply, the blue wire on the top of the board



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    Default Re: hobby cnc ez board trouble shooting help

    apart from the soldered connections to the 24V regulator every thing else on the board looks OK

    one possible thing that needs investigation is not all switch mode power supplies work correctly when connected to stepper drivers that "chop"the motor supply to control the motor current

    try disconnecting the motors and setting the switch mode power supply to 26 or 27V

    assuming the 24V regulator U5 is working you should have +24V on the tab that's connected to the output lead

    you should also have +5V on the output of U4 with U5 working
    (or when you have at least +7V going into U4)

    if every thing works with all of the motors disconnected
    add one at a time with the power off and then re test

    if it all works with the 3 stepper motors - great

    if not ,

    it may be worth while replacing U5 (LM317HV) any way
    and trying it again with your original linear power supply

    may be I'll have to think of more tests to prove if its the new power supply are not compatible with the EZ board
    or its a fault on the EZ board depending on your test results



    John



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    Default Re: hobby cnc ez board trouble shooting help

    I will look at it when I get off, I think I can rule out the power supply because I had the failure with the unregulated power supply as well. My next test will be with nothing connected to the 24v fan connection.

    Thank you for the help



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    Default Re: hobby cnc ez board trouble shooting help

    Quote Originally Posted by rotccapt View Post
    woodworkerb, if u5 were to be the culprit would it cause u4 to read low? during the last failure i read 3v at the 5v test pad
    Yes. U5 "feeds" the regulated 24 Volts to the input of U4 (the 5volt regulator). So if U5 was damaged, outputting less than, say 5.5V, then that would indeed cause U4 to read low.

    Let me know if you need some replacement regulators (brian@hobbycnc.com)

    I can also throw the board on my "known good" test jig for you.

    BrianV

    WoodWorkerB
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    Default Re: hobby cnc ez board trouble shooting help

    Thank you for the info, I may revisit this board and keep it for another project but I decided to upgrade to a more capable set up. I am fairly confident the reg is the problem though.



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    Default Re: hobby cnc ez board trouble shooting help

    Cool. The offer to test and/or replace the regulators is still on the table. Just let me know. I want you to use the board and be happy with it. Now might be the right time if you're not using it.
    BrianV

    WoodWorkerB
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