Need more inputs, Parallel Port. Ideas

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    Default Need more inputs, Parallel Port. Ideas

    Hey guys,

    I've run out of inputs for my Parallel Port break out board. 3 axis with 2 motors and sensors on one axis (4 inputs), E-Stop and I'm out. I only want one more for tool touch off sensor. Easiest thing I can think of is adding another parallel port and break out board which will give me plenty but I'm wondering if anyone has an idea just to get a cheap extra one input?

    Should add, I'm more than happy with the performance of the Parallel port. Just lacking an input. The break out board is super cheap for what it does too.

    Happy Days.

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    Default Re: Need more inputs, Parallel Port. Ideas

    Arduino and modbus, but imo the parallel port is easier.

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    Default Re: Need more inputs, Parallel Port. Ideas

    If you need just one port, one that doesn't need to be high speed, you could always use a handshaking pin on an RS232 port. Of course this depends upon having can RS232 port to exploit. Further you would have to write your own code to monitor the port. I've actually done this on the out going side to control an optical isolator for a project. Fully compliant RS232 ports drive at about 12 VDC with enough current to toggle an optical isolator. Sadly on laptops you often don't get compliant ports even if they are physically there.

    The biggest problem here might be speed, I was using Python at the time and controlling the port with a high level library so really have no idea if the tis fast enough for anything you might want to use.

    A second option would be to program an Arduino as an I/O device ideally plugged into an isolated digital I/O board. Arduinos are dirt cheap and as such cost effective enough even for single bit I/O.

    The third option of a parallel port board isn't bad at all. These can also be found dirt cheap especially for older I/O buses.

    A fourth option would be to use an FTDI solution: USB to RS232/422/485 Modules for RS232 adapters or some of its chip sets which may support parallel I/O.



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    Default Re: Need more inputs, Parallel Port. Ideas

    Thanks for the info guys. It gives me somewhere to start looking. I'm using LimuxCNC. It seems Mesa boards are hugely popular with Linux but also cost. Apart from one extra input, I don't know why you spend so much extra money.



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    Default Re: Need more inputs, Parallel Port. Ideas

    Quote Originally Posted by joel0407 View Post
    Thanks for the info guys. It gives me somewhere to start looking. I'm using LinuxCNC. It seems Mesa boards are hugely popular with Linux but also cost. Apart from one extra input, I don't know why you spend so much extra money.
    For small machines, there is nothing wrong with a parallel port and adding a second one is a good option. If you are running servos then you have to either go with pico or mesa or a couple of others. For plasma, Mesa is a no brainer. Think about it. Ethernet to keep the PC away from the noise, a USD $69 torch height option and 16 outputs and 32 inputs (which I think I have used 31 of) Not to mention 5 stepgens that blitz par port performance, some A/D inputs, 2 MPG inputs plus virtually infinite expansion. It is a pretty amazing ecosystem and once you buy into it, you'll never want to go back.

    Rod Webster
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    Default Re: Need more inputs, Parallel Port. Ideas

    Quote Originally Posted by rodw View Post
    For small machines, there is nothing wrong with a parallel port and adding a second one is a good option. If you are running servos then you have to either go with pico or mesa or a couple of others. For plasma, Mesa is a no brainer. Think about it. Ethernet to keep the PC away from the noise, a USD $69 torch height option and 16 outputs and 32 inputs (which I think I have used 31 of) Not to mention 5 stepgens that blitz par port performance, some A/D inputs, 2 MPG inputs plus virtually infinite expansion. It is a pretty amazing ecosystem and once you buy into it, you'll never want to go back.
    I don't know how popular servos are? From what I've read they aren't all that popular.

    Comparing a second hand PC for $25 and a parallel break out board for $12 (or close to, can't remember). I think you mentioned to me before that it's easy enough to run a remote terminal to the PC running the router. So it's not that hard to have separation from your main PC. For $37 it's a bloody cheap option. I'm keen to post a video of my machine once it's finished because I think it's bloody fast. I'm wondering what's the point of the super stepgen performance?


    Happy Days.



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    Default Re: Need more inputs, Parallel Port. Ideas

    Quote Originally Posted by joel0407 View Post
    Hey guys,

    I've run out of inputs for my Parallel Port break out board. 3 axis with 2 motors and sensors on one axis (4 inputs), E-Stop and I'm out. I only want one more for tool touch off sensor. Easiest thing I can think of is adding another parallel port and break out board which will give me plenty but I'm wondering if anyone has an idea just to get a cheap extra one input?

    Should add, I'm more than happy with the performance of the Parallel port. Just lacking an input. The break out board is super cheap for what it does too.

    Happy Days.
    Can't you share an input pin for two of the limit switchs the Z axis and any other one?



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    Default Re: Need more inputs, Parallel Port. Ideas

    Quote Originally Posted by Tutu View Post
    Can't you share an input pin for two of the limit switchs the Z axis and any other one?
    All the limit switches are in series with the E-Stop. so only one input for all the limits. Each axis only has one homing sensor. I guess where my setup is a little less common is I have 2 screws and 2 motors on my Y axis. That means I need 2 homing sensors for that axis to square itself when it homes.



    Happy Days.



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    Default Re: Need more inputs, Parallel Port. Ideas

    Quote Originally Posted by joel0407 View Post
    All the limit switches are in series with the E-Stop. so only one input for all the limits. Each axis only has one homing sensor. I guess where my setup is a little less common is I have 2 screws and 2 motors on my Y axis. That means I need 2 homing sensors for that axis to square itself when it homes.



    Happy Days.
    That's pretty common it's how mine is setup share homing input pin Z and X you only need individual pins for homing on the Y axis.

    I have no Z homing switch so only need 3 inputs anyway.



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    Default Re: Need more inputs, Parallel Port. Ideas

    Quote Originally Posted by joel0407 View Post
    All the limit switches are in series with the E-Stop. so only one input for all the limits. Each axis only has one homing sensor. I guess where my setup is a little less common is I have 2 screws and 2 motors on my Y axis. That means I need 2 homing sensors for that axis to square itself when it homes.



    Happy Days.
    What's the point of having a home switch on Z? Disconnect tha and use the input as probe. Or add another parallel port. These are the cheapest and simplest options.

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    Default Re: Need more inputs, Parallel Port. Ideas

    Sounds like you have dedicated homing sensors in addition to limit switches. Since in this case the homing switches are only used for homing, it may be possible to use the same pin for the homing sensor and a probe either in parallel or series as appropriate. I believe that this is possible in LinuxCNC and would get around needing another PP.

    As for why a home switch is needed for Z, I can't speak for how others operate, but as an example:

    If I discontinue machining a part for the night or whatever, I shut down the machine and then when I come back the next time, all I have to do is turn the machine on, home, and resume where I left off. If I didn't have a Z axis home switch I would have to touch off to re-establish my Z-zero before machining. If using multiple tools and the break in the action is not during the use of tool #1 then I would have to re-insert tool #1 touch it off and then go back to whatever tool was the current one. This is because I use tool #1 as the baseline too and the tool lengths of all other tools are relative to the length of tool #1. With Z-axis homing none of this is necessary.

    Another reason for z-axis homing in my opinion is because it sets the envelope of the Z-axis. Without homing the Z, things like the G28 or G30 positions are not consistent among other things.



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    Default Re: Need more inputs, Parallel Port. Ideas

    Quote Originally Posted by 109jb View Post
    Sounds like you have dedicated homing sensors in addition to limit switches. Since in this case the homing switches are only used for homing, it may be possible to use the same pin for the homing sensor and a probe either in parallel or series as appropriate. I believe that this is possible in LinuxCNC and would get around needing another PP.
    Now this is interesting. I might have to do a little reading. I think you are right. I can set the same pin for both. The difference will be the direction of movement for each action. I'd need to move Z off home prior to touching off. Since my homing senor is a proximity sensor, Z approaches home at a higher speed, trips sensor, backs off slightly then approaches at a slow speed for better accuracy. Once tripped, Z will proceed past the sensor for a predetermined distance. I'd need to back off home until the sensor was released then touch off.

    I like it. I'll give it a go. Might confuse things but worth a try.

    Happy Days.



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Need more inputs, Parallel Port. Ideas

Need more inputs, Parallel Port. Ideas