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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Steppers, Drivers and Power supply
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  1. #1
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    Steppers, Drivers and Power supply

    Hi,

    I am a machinist by trade and have run a few cnc's but mostly conventional machines. Have done some editing but no actual programing.
    This is my first post and I would first of all offer Thanks in advance for any and all replies due to the fact I may not be able to respond as soon and as often as I should due to work commitments.
    I am in the process of collecting needed items to convert an Enco round column mill to cnc. I've had this mill since about 1992. It is the heavier version with the 4" column.
    I have 3 Pacific Scientific/Jetter/Bautz 500 oz step motors rated at 5.6 amps bi-polar, 65 volts, 133 watts and 1500 rpm. All 3 are identical.
    I have an opportunity to purchase Centent CN0143 drivers for these that are rated at 7.5 amps and 60 volts.
    Also have a chance to get a 50 volt- 10 amp power supply. It has a 50 volt torroidal 500 volt/amp transformer, 2-10,000 uf 50 volt capacitors and a 25 amp 600 volt bridge rectifier.
    My question is will all of these components work together or do I need to look at something different in the way of drivers and transformer. Seems to me they should all work together. The only thing I think may need to be changed is going to a larger power supply.
    BTW, I don't know beans about electronics.

    Would welcome any and all replies.

    Thanks,
    Bob Garner

  2. #2
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    Basically maybe....is the 50 volt toroidal transformer....is that the secondary AC or ? I that is the secondary AC then when you do the 50 VAC x 1.41 to get the DC you will exceed the Centent ratings......

  3. #3
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    With all due respect, before I'd start trying to do component integration all while not knowing beans about electronics, I be FIRST inclined to eliminate my electronics knowledge deficiency.

    Component integration involves the basic application of Ohm's law. From there, you learn to apply the power equation which is a fundamental requirement of mixing/matching power supplies, motors and/or driver cards.

    To match the motors and drives, you need to have all the motor side power requirements matched as in matched for current (output vs draw) and voltage (AC or DC). Transformers turn AC high to AC low but rectifiers turn a low AC voltage into a DC one roughtly 40% higher, depending on filtration done by capacitors.

    You'd no more plug an electic shaver into 220v range plug than a 12vdc trouble light into a wall socket. Yet, you want to mix-n-match a bunch of seemingly randomly found items with specs that are not quite adequately matched/specified to determine interface viability. Not a good idea.

    DIY cnc invovles:
    1. buying a pre-engineered kit wherein parts are prematched by folks well versed in electronics and/or component integration. You then bolt it together but the seller has done the engineering and prior trouble shooting for you.

    or

    2. Figuring out what you want to do and then looking for components that will fit your needs and properly integrating them together. "Integration" typically involves electrical and/or mechanical engineering that can be tough to do via message board input. YOU do the engineering and then YOU bolt it together and YOU trouble shoot it.

    If you want to follow your hunch "Seems to me they should all work together", go ahead and bolt the stuff together and see what happens. I wouldn't cuz I don't think enough is PROPERLY known about the component specs to take that risk.

    Anyway, if it works, cool. If not, you are about to take the first and perhaps an expensive and surely an exciting step in learning how to eliminate your lack of knowledge and experience with electronics.

    It's not the end experience but rather the journey that provides the adventure.

  4. #4
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    I agree with NC Cams. Get at least a little knowledge first, especially before messing with 10A supplies. It won't take long to learn what you need to know, and it is pretty fun to learn, especially if you get to apply your knowledge right after learning it.

    A few things I noticed about the original post though... These are just basics, to get you started, there is probably a lot more, but I do not have the components here to look at.

    Make sure that the supply/system is adequately fused.

    When you do decide to take the plunge, make sure you ground the system correctly.

    Capacitors will maintain a charge for a period of time... use a bleeder resistor/LED to make sure the system is fully powered down before working on it. I once got a shock from a capacitor that got a charge from being shipped across the nation, it picked up static electricity during shipping (I assume).

    Make sure that you can shut off the system BEFORE the Power Supply, in case something nasty happens inside the supply you can kill the entire system.

    Is the system protected against back EMF? That would be a good term to Google.

    Are the drivers "chopper" types are do they require ballast resistors. Google again will start you off with this info.

    You came to the right place, there is a wealth of information here. Keep asking questions! Just be careful before with the electronics... 10A can easily kill. You are a machinist and I can only assume that you have great respect for machine safety. Electronics are the same way, once you have an appreciation for the hazards you will garner a respect for the precautions required.

    mjarus.

  5. #5
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    Quote Originally Posted by mjarus
    . 10A can easily kill. .
    A little clarification on lethal shock.
    Although of course 10amps flowing through the human body would certainly kill you, only 100 to 200ma is considered dangerous and above 500ma can be lethal.
    To get 10amps to flow, a voltage would have to be available that normal people do not come across, this side if Lightning.
    If you consider a 12vdc auto battery capable of 200amps, people handle these all the time and work on automotive electrics all the time with the only saftey concern is a burn from shorting a terminal.
    The reason is, the normal resistance of the human body restricts the current at this voltage to below danger level.
    When working on higher voltages than 24v (BTW ac is considered more dangerous) it pays to keep one hand off equipment or in your pocket, If you receive a shock from hand to elbow, this has less of a hazard than from hand to hand.
    Fortunately, In most cases, the involuntary action of the shock, will often cause your hand to jerk away from the source, Unfortunately, if you cannot release your hand, the resistance starts to drop rapidly, causing further current to flow. (chair)
    Ask anyone who works in the electrical/electronic industry and they will probably tell you that they have had their share of Jabs.
    The highest I have had is from 18,000v from the side of a CRT,(which happened to be ON
    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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    First of all, I would like to thank you all for your replies.

    Second, I'm very aware of the dangers of electricity having stuck my finger in a lamp socket in my younger and dumber days. Also, with spark plugs. Quite a shock I might add!

    I will have someone very knowledgeable (Electronics Techs) either put this thing together or guide me through it. Rest assured it will be put together properly with all safety precautions observed!

    I have not been able to discuss this with them as yet.

    More info on the centents can be found on their website; www.centent.com. These drivers specs are; power supply 24vdc to 60 vdc. Phase current (CN0143) 1.5 amps to 7.2 amps, switching frequency 20 khz to 60 khz, power dissipation 30 watts (max), resolution 10 uStep (fixed).

    Power supply is Ebay item 7618911525.

    Again the motors are Bi-Polar Pacific Scientific Bautz (part number B213437D200B038L)/Jetter (model 21-3437D200-B038L-2), 65 volts which is max, 5.6 amps, 133 watts, 1.8 deg. I searched for more info on the specs but was unsuccessful.

    I have looked at some of the packages (the very few I have found), and most are cost prohibitive for me. If I had a Sherline or Taig, it would be much less costly since their requirements are lower than is required for the Enco mill. This is why I am looking at the above items that are more in my price range.

    I have looked at Ohms law and other things needed to understand this whole thing but I have not found anything that is "integrated" with all of the "what if" scenarios where a person such as myself can understand it all and put it to practical use. Most are written for someone very familiar with these sorts of things. Possibly my search skills need to be improved.

    Basically, I was just looking for information. I have plenty of time since it won't be accomplished until I retire in a year or so. If someone can direct me to (links) or other references so that I may understand better the nature of electronics, I would appreciate it.

    Also, what information would any of you need to find out if these components would work together? I believe the prices are reasonable but if they won't I will surely not buy them.

    Being a machinist and very mechanical type person, I believe one needs to follow each required step to reach the desirable end result, but if those steps are not known then the end result can not be reached. For instance, I have the motors which from what I have read are a minimum to drive the ball screws on my Enco mill at a 2-1 ratio (using pulleys and belts) and receive acceptable feeds during the milling process. Mechanicals won't be a problem. I have plans for them. They are 5.6 amps. I have been told that that the centent drivers will drive these motors in an acceptable fashion. I understand from reading other posts that the power supply should be sufficient as well since one does not want to drive the motors at full voltage.

    Again,
    Thanks for any and all replies,

    Bob Garner

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    I didn't mean to scare anyone away with the warnings, but safety it pretty important when dealing with larger supplies.

    the normal resistance of the human body restricts the current at this voltage to below danger level.
    I agree with this statement under normal conditions, but there can be issues when there are mitigating circumstances such as sweaty fingers, or metal shavings covering the fingers, or both! In addition, there are other concerns with high voltage/current such as fire hazards.

    Again, I am not trying to scare anyone, we all deal with high power loads in every day life, we just might not always be directly in contact with them. After reading the poster's reply, I am pretty sure that he will do just fine. :cheers:

    Anyways here are some good links to get you started:

    http://pminmo.com/ Phil is on this board too, great guy. Good links and explantations.

    http://www.discovercircuits.com/list.htm All kind of links to schmatics, look at power supplies schematics.

    http://www.woodyweb.ca/~woody/controller.html Decent read.

    http://www.ibiblio.org/obp/electricCircuits/index.htm Great electronics references, for free!

    http://www.uoguelph.ca/~antoon/circ/vps.htm An example PS schematic. Not what you need for your project, but may be a good read.

    Hope these help.

    mjarus.

  8. #8
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    Bob,

    The motors drivers and Power Supply you've listed will work.

    The only 'integration' issue you really have is will the motors be able to drive your machine as rated? You've already answered that and are expecting to use them with a 2:1 drive ratio.

    Couple of points to note;

    PacSci motors are rated differently to other vendors. The 65v is the maximum the motors should be driven at. Other vendors rate thiers as 1.8vdc etc.. 1500 rpm is the max rated rpm and will require full power and commercial drivers to produce that. If you look at the torque curves for the motors you'll see the torque drops with speed and so don't plan on running these at 1500 rpm.

    you'll need to current set the drivers to match the motors 5.6a max as shown.

    power supply looks good. 50vdc is about right for the 65v motors and in spec for the drivers. Linear supplies are prefered and the centent drivers, from their spec sheet appear to dump back emf ( power produced by the motors rotation acting as a generator) to the supply which could be a problem with a switching supply. The supply is well rated for the drivers unless you expect all three axis to be running consistantly at once. In which case you might want to consider a bigger supply.

    I seem to remember the centent drivers where designed by the same guy who now produces teh Gecko Drivers. Have a look at Geckodrive.com and look at the support doc there. Its very useful and will provide all the information you'd need to put such a setup together..

    Andrew

  9. #9
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    Thanks for the links and answers. I will have to read up quite a bit more on this. I have printed the Gecko info and have looked at the others as much as I could today. Will go back as I have time and read and read some more.

    I do not believe I will be running more than 2 drives at a time. Will most likely use it for small model railroad work at first. I'm also not going to be looking at very great speed. Anything is better than hand cranking this thing! I've hand cranked a lot of machines in my time and it gets old real fast. No production planned to speak of. I thought about powered x and y feeds with digital readouts, but that would cost almost as much if not more than this conversion will cost.

    Anyway, Thanks again for all of the information.

    Bob Garner

  10. #10
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    Your post #6 gives a FAR different impression than post #1.

    This is why so much emphasis was placed on suggesting that you try to eliminate your electronics deficiency/ies. Moreover, it is all but impossible to answer such general questions in a specific way when one has no idea of the technical capabilities of an inquiring member - especially one who admittedly is a neophyte with electronics.

    THe integration of a CNC system is NOT like staging a domino fall - as in you set them up and knock over the first one and the rest fall in reaction to the initial input. Rather, the project is a bunch of LITTLE projects strung together that you knock over in planned sequence or when an obstruction rears its ugly head.

    In this case, you've apparently decided to buy a group of parts that are reasonably close to being bolt together (per post #8).

    That's much better than a hodge podge of disjointed stuff that isn't even in the same zip code. To deal with the electronics, you simply solve Ohm's law multiple times, piece by piece as you tie stuff together (reading the manuals along the way - please do try to get them as they WILL come in handy sooner or later).

    You first see how much power the motors will draw in amps at the optimum voltage at max load. You then mate them with properly chosen/sized driver cards. YOu then create a power supply with enough OOMPH that will supply it. Add a dab of capacitance for surge demand and you're home free.

    It is that simple for some but, including myself, it takes a lot more figuring and baby sitting than that to make a go of stuff - all the while NOT letting smoke out of expensive electronic parts or blowing the meter off the side of the house.

    Using Ohm's law and the power/current formulae, you then choose the wire. Since you're going to gear down (2:1 if I recall) your current should NOT be as great as if you were at 1:1 but not you're going to want to run as high a voltage as possible to get/keep motor speed up and current draw down. A nip here, tuck there, cap here, fuse there, limit switch at ends of travel, some wire and you're home free....

    As you assemble/link the parts together, you solve the problems as they occur. Better yet, you "figure" out what you need in the way of power/amperage/wire size, etc. as part of your system integration efforts. How?? Draw a schematic and then have it checked. THEN follow it being sure to label the wiring - nothing worse than trouble shooting 35 all black wires that are all the same gage and going to goodness knows how many circuits.

    THis way, you have properly sized and "integrated" parts that can be traced rather than a hodge podge of stuff that may or may not work without doing funny things.

    There is an important thing to remember: a system is engineered by plugging in the variables and solving the power and Ohm's law and ohter equations to determine engineering viability. It is wired in an organized and workmanship fashion.

    Any "i dunno" for a critical input value will unfortunately generate a "i dunno" for an answer as well from even a well versed systems integrator - unless they have empirical experience with something similar and that sort of experience goes a long way.....

    When the tech data isn't available, reasonableness has to be used to decide if it is "give it a shot" time or take a SWAG and see what happens.... For example, if your going to draw 10 amps, 12 gage wire is "reasonable", 22awg DB9 cord isn't even though it has a much nicer and readily sourceable package.

    Keep in mind that there are times what systems fall into the "that can't work" and it does. Sadly, there are also times when "it should work" and clearly doesn't (as smoke billows out of every existing orifice and some new ones that weren't there before)....

    The old addage of "measure twice, cut once" pertains to DIY CNC except you "figure it out several times, try it and then figure some more when it still doesn't work".....

    When it does finally work, it will seen obvious as to how simple it all really is and all this techno babble is just a ruse to scare away the sissies...

    Enjoy.

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    and all this techno babble is just a ruse to scare away the sissies...
    That is why I like reading NCCams posts... cuts straight to the chase.

    After working my whole career in the tech sectors, I have come to realize that something either is gonna work or it ain't. Sometimes you can control if it will work, other times you can just mitigate the factors working against you. Many times if you are trying something new it is a crapshoot. Then once you get it to work, you form your hypothesis on why it worked and claim you knew it all along. :cheers:

    When it doesn't work... either blame someone else or hide the evidence .

    mjarus.

  12. #12
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    Quote Originally Posted by NC Cams
    Using Ohm's law and the power/current formulae, you then choose the wire. Since you're going to gear down (2:1 if I recall) your current should NOT be as great as if you were at 1:1 .
    You sure about that? I'm pretty sure the current will be the same.

    A chopper driver (centent, gecko etc) is a current control system. The coil is energised until the set current is reached and then the driver 'chops' the supply to maintain that current until the coil is no longer energised. Higher voltages mean the required current is achieved earlier and for longer so increasing the effective power applied and the produced torque and speed. Lower voltages mean the current is achieved slower so reducing the net power.

    The driver will try and maintain the set current regardless of the motors speed, even if the motor is stationary - unless the driver has a current reduction facility. Driver certainly doesn't care if the motor is geared or not.

    As the speed increases the EMF produced by the motor increases and so works against the driver supply and so does reduce the effective power in the coil but the current supplied by the driver will not change.

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