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    Default Need help on hooking step driver to paralle port

    Hello,

    I'll start by saying I'm trying to do various tests in order to learn enough to build a small cnc router for cutting plywood (so i'm thinking of 2 or 3 axis are needed).

    I'm not very knowledgeable on the electronics part and because I'm doing this on spare time (would like to have this finished by the end of the year if possible) and because money amount is limited I would like to do a balance of electronics learning vs buying expensive already built parts.

    To that extent I was thinking of using the computer (an older one) and a pci parallel card (those I have and tested for the moment) to control the future cnc.
    I was looking around the online shops and has hoping to use a step motor like this: https://www.pololu.com/product/2267/specs along with either stepper driver like this https://www.pololu.com/product/2133 or this one: https://www.dfrobot.com/wiki/index.p...r_SKU:_DRI0043 .
    I'll mention here that I'm planning on using a computer standard power source for the motor.

    My question is: https://www.pololu.com/product/2133 seems to be easy to connect to the lpt port but I'm not sure I understand the tb6600 (https://www.dfrobot.com/wiki/index.p...r_SKU:_DRI0043) , I see the tb6600 needs 5 volts, does it need strictly 5v ? or is ~ 3.xx volts good enough too ? My lpt port apparently gives me 3.24 V.

    Do I need something else between the driver and the lpt port ?

    Thanks in advance.

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    Default Re: Need help on hooking step driver to paralle port

    Quote Originally Posted by andrei_123 View Post
    Do I need something else between the driver and the lpt port ?
    Hello,
    Yes the thing you are missing between the LPT port and the stepper driver is called a breakout board. It buffers the LPT control lines and provides enough current to drive the PUL, DIR and EN optocoupler LEDs inside the stepper driver.
    Have a look on eBay there are plenty of low cost ones available.
    If the tb6600 specifies 5 volts then that is what you should be providing. A small power pack is only a few dollars or if you have an old cell phone charger that is probably 5V too.
    David



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    Default Re: Need help on hooking step driver to paralle port

    Hello David,

    Thanks for the quick answer. Then if TB6600 needs specifically 5 volts to trigger it then maybe I'll use the other driver which apparently accepts input voltage from 2.5 V to 5 V from parallel port.
    Unfortunately I'm not very familiar with what a breakout board really does. if the driver chip has optocouplers inside it do I still need some protection between parallel port and driver ?
    This breakout board, is it really necessary ? I'm trying to be as basic as possible since I can't easily get stuff from ebay, I'm looking through the online shops in my country and these breakout boards apparently are quite expensive, the ones I saw cost as much as 5 step motors.

    Thanks



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    Default Re: Need help on hooking step driver to paralle port

    What are you trying to build specifically? Can you give me the machine dimensions? We can give you a better breakdown of what you need and what they do if you can tell us that.



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    Default Re: Need help on hooking step driver to paralle port

    @jonnyk2

    As I said in the first post my goal is a small cnc router for cutting plywood with 4mm thickness. As for dimensions I am not sure because I wanted to see how powerful the motor really is, but I guess I am hoping that the machine will have a base large enough to accommodate a plywood of sizes 297mm x 420mm. Optimistically I would like the base to be 420mm x 594mm but again I don't really have a solid understanding of everything that is needed and I am experimenting at every stage I am going through.
    Do you want some other information ?



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    Default Re: Need help on hooking step driver to paralle port

    Hi,
    Yes you can use a direct connect type driver module that accepts logic input signals from the LPT port but then the bridge and motors share the same ground as the printer port. As you are making a desktop CNC with NEMA 17 motors you may get away with it if you are careful with grounding, but it's all getting a bit hairy. If you are trying to save money and learn about electronics I would recommend you scavenge old stepper motors out of discarded equipment like inkjet printers, scanners, photocopiers etc. Back in the day I used to get my free NEMA 17 steppers out of discarded 5 1/4" floppy drives. Photocopiers often have bigger steppers that may be more appropriate for what you want to build as NEMA 17 is a bit on the small side.
    Anyway I'm sure you will learn lots and have have plenty of fun. CNC is a great hobby.
    David



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    Default Re: Need help on hooking step driver to paralle port

    So what you're saying is that I should use a different groud ? Is it good if I use the separate pc power supply ground ? the one I intend to use for the motors ?



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    Default Re: Need help on hooking step driver to paralle port

    You absolutely, positively, beyond ANY shadow of a doubt do NOT (NOT NOT NOT) need anything between the parallel port and the stepper driver boards. You maybe /should/ have a buffer, or a break out board, but that is NOT required.

    I've built multiple devices like this with an old parallel cable. Just cut the printer end off and ohm out the wires. As long as you are using a standard PC desktop with a standard parallel port, it will work just fine.

    A buffer can help to increase speed or get the correct voltage levels if you are using a parallel port on some laptops.

    Opto-isolation can help protect your PC from getting fried if the drivers short out. I don't trust it, and always use old PC's that can get fried without costing me anything.

    A break out board just makes it easier for people who don't know how to ohm out a cable. I recommend you learn. It isn't hard.

    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: Need help on hooking step driver to paralle port

    ok thanks a lot for the answers so far. I am thinking now that maybe I want to build a breakout board for the parallel port. Can someone help with some simple schematic on this ? Also what is the diff between a buffering and non-buffering breakout board ? I guess I need optocouplers on it , some resistors and probably a separate 5 v power supply on the other side of the optocouplers.



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    Default Re: Need help on hooking step driver to paralle port

    There isn't a lot to a break out board... it's really just adapting the parallel port connector to whatever terminals you want. As an example my (somewhat different) break out board schematic is shown on this page:
    techref.massmind.org/techref/io/stepper/linistep/4axis5build.htm
    and the only real parts are JP3 and J3 in the lower mid left area of the schematic. In my case, JP3 is a 2x40 header because that allows me to modify old IDE hard drive cables to connect to PMinMO standard drivers, but yours could be a set of screw terminals or whatever you want.

    If you are dead set on opto-isolators, then you need to keep the two halves TOTALLY separate, including ground and logic power. So you need two power supplies (the parallel port doesn't put out enough power to run optos reliably. And you are still hoping the PC side power supply doesn't fry. It's a good idea to use a spare power connector on the PC's own supply, but I've never seen that done. On the CNC side, you need a logic supply (5 volt) anyway, so that's no loss. Find an opto you like and follow the datasheet.

    I personally don't put much faith in opto-isolators, and I've seen them cause a lot of problems, so I just use old PC's that I don't care about to run the system and I design on my nice PC... I call it "full PC isolation" LOL.

    Anyway, good luck with it.

    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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Need help on hooking step driver to paralle port

Need help on hooking step driver to paralle port