Break out boards 



This page describes 2 designs wich I made for personal use, these are the result of several versions wich I have developed and used for many years. Learned a lot from problems and minor issues wich I encountered during this time. The first ones had optocouplers on the BOB, for these I also used a proprietary connection scheme wich worked fine but wasn't optimal. Commercial drive's do have the opto's on board, this is a problem if you want to use one of these.
Then came several other designs (like USBCNC, Planet CNC and others) wich use the PMinMO connection scheme and use this interface for the connection to commercial drives.
It was then obvious that a BOB design had to be compatible with the above to assure maximum flexibility.

Let's go back in time: The parrallel printer port was originally designed a long time ago, even before the first IBM PC was born, it was used on mini computers and also known as Centronics or Dataproducts ports. IBM implemented the Centronics version for their PC's. During these early day's the port was used for dot-matrix or drum printers wich had stepper, servo motors and a lot of solenoid's... Sounds very familiar to what we have in our CNC machines.
Almost all printers at that time had a signal input configuration to filter noise and spikes and worked without problems, the later cheaper inkjet and laser printers didn't have this and problems occurred with longer cables and output ports with weak signals.
Sometimes I encountered similar problems with the first simple BOB designs, below is the input scheme wich is loosely based on those early printers, I use it now for some time and it works fine.

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The portion on the right is the PMinMO 10 pin flatcable connector and a simplified connection diagram to a commercial drive. The left hand portion has the filtering and signal conditioning. A printer port has 12 output signals so the above is needed 6 times. It might look overly complicated at a first glance but it's just some resistors (or array's), cap's and 2 chips, total cost for this will only be a few dollars or less but it will still work in marginal circumstances and also on Pc's and laptop's with weak output signal level's.

The same thing happened with the outputs of the BOB to the port, several scheme's were used for the limit, home, estop etc.. Final result is a concept that can be used with normal NO or NC switches but also with proximity sensors with either NPN or PNP outputs. A mix of all these is also possible with this design:

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An optocoupler is used to protect the port from the switch wires running all over the machine wich could pickup noise, spikes and eventually a short with lethal voltages for the port inputs, this is where most ports die: on the inputs not the outputs. The components are dimensioned for operation on 12Vdc, an optional regulator for this is on the BOB. A led indicator shows the status. Below are some examples of possible connections.


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Pictures, schematic, PCB layout and assembly instructions are available under the respective tabs.

On offer is the PCB and for those who want it real easy with no hassle: there's also a full kit available.
Price for the PCB only: 8,00 Euro
Kit with PCB and all components included: 35,00 Euro