This project will increase the usability of any Mill or Lathe with minimal cost. Whats a DRO? It stands for Digital Read Out and is connected to the axis on a milling machine or lath to show the current location of the cutter. This makes it much easier to make things, rather than reading the dials and counting in your head. The productivity gains from adding a DRO are huge.
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| Traditional DRO System |
Unfortunately DRO's tend to be realy expensive, some systems cost more than the home workshop equipment they are connected to. When I started to look at options I quickly ruled out the traditional 7 segment LED displays for the following reasons:
- Too difficult to run - A three axis system might have 25 or more modules!
- Too much current draw - It adds up!
- Too expensive - Again, the cost adds up
I was also keen to make the system flexible, so that some users might have one axis, others 4 or more. Designing the PCB and control systems to be modular was a headache.
As an alternative to 7 Segment LED modules, I explores LCD's. However the readability was not so good and the same issues with flexibility etc weren't resolved.
Finally I decided to produce a PC based system. It is pretty easy to get your hands on a low cost (free) older PC running XP, small LCD screens (14") are worthless and both can be mounted easily high up next to the machine (or in between a mill and lathe for a shared setup).
By using the PC as the display and input system the costs are kept down, the system is flexible and there is plenty of scope for fancy functions to be added later (like pseudo CNC).
The above pictures are of the prototype system currently under development. The board on the left is the optical transceiver option (for linear\rotary position) and the board on the right is the hall switch option (for spindle RPM).
The optical transceiver and matching linear strips are from US Digital. The USB bridge is an FTDI FT232RL and currently a Microchip PIC18F1220 is loaded as the micro. Power is derived from the USB bus with a P channel mosfet ensuring the board does not draw excess current during suspend mode.
The pins exiting the side of the PCB are for development programming and will not be there in the final version. Also, the wires jumping across the micro are there to correct a mistake in the circuit which seems inevitable despite checking are rechecking (damn microchip and there use of the easily forgotten vdd \ vcc). The boards are 55mm x 32mm and were produced by PCB Core. The final units will be encapsulated in epoxy for water resistance.
I will keep placing updates here as I go. If you have any interest in the system please drop me an enquiry using the form on the right.
