The soldering unit that attaches to the gantry along with its controller and programming pendant will be used "as is". In addition to the pendant the soldering unit has a external control cable that plugs into the main base.
In brief, the control of the soldering module via the external interface is
- 5 lines are used to select which of the 30 sdoldering blocks (pre-programmed soldering operation) is to be performed
- 1 line to sent the "Start" pulse to the unit.
- 1 line to receive the end pulse once the soldering operation is complete
- 1 line to receive an error signal from the unit.
So, to solder a joint, the base moves the gantry to the correct X,Y,Z position, then the Soldering unit is commanded to perform one of the 30 soldering cycles. All very simple.
For the conversion, I plan to use Mach3 for the CNC control software and a SmoothStepper. The reason for the SmoothStepper is that it has the equivalent of two buffered parallel ports on it. I plan to use port 1 to control the X,Y,Z Base. So that's the 3 axis stepper drivers, the 3 axis home switches, and the halt and start switches. The 2nd parallel port will be used to control the Soldering head unit. By using the SmoothStepper, the connection from the PC to the robot will be a single USB cable.
The Shuttle PC I'm using can be seen below.
As to the computer, at this stage I'm planning to use an all-in-one Shuttle X50 V2 15" Panel PC. It has;
- four USB ports,
- 15.6" touch screen
- VESA Mount
- Serial Port
- NO Parallel Port
The only Issue I see is that it has an Atom Intel® D510 dual-core processor, so hopefully it will work with Mach3. I plan to have it mounted on a stand adjacent to the main Unit. Being a touch screen, I may be able to get away from the Keyboard and mouse. Not sure if that is going to be possible but we will see.
Images of the electronics are attached.
Below is the base of the unit containing the electronics. The three stepper dirivers can clearly by seen, along with the 24Vdc switch mode power supply.
Visible are two PCBs. In fact there is another sitting under the one on the right.
The PCB on the left is primarily the interface board for control of the external Units such as my soldering unit. All of the output lines are switches by relays. The external units are connected by a 50 pin centronics connector. THE connector to the left is for the base unit's teach pendant. I will be replacing this board with my own that will interface to the Smooth Stepper Port two.
The boards to the left contain the processor, memory, RS232, etc. These will be replaced by a small breakout board that will interface to the SmoothStepper port 1.
I plan to use the existing wiring cables, so my boards will been to have matching connectors. I want to just plug in as much as possible without cutting anything.
As can be seen the base is very solid and cast. The Y axis stepper is clearly visible. Initially my plan was to replace the stepper drivers with a Geckodrive G540 4 axis stepper drive. On closer inspection of the motors, I discovered that they were Vexta 5-phase motors and are no compatible with the Geckodrive G540 bi-polar drive.
I then contemplated replacing the motors as they seemed to be size 23 steppers. I removed one and did a trial fit of one of my motors. What I found was that the aligning boss on the Vextra motors is fractionally smaller than the standard size 23 boss. Also the bolt hole mounting pattern was different.
In the end I decided that it was simpler to use the existing Vextra 5-phase stepper drivers until I discovered that they take a Clockwise and Counter Clockwise input, rather than the more common Step and Direction inputs that Mach3 generates. so nothing is ever as simple as it first seems.
So now my plan is to put a set of Step/Dir to CW/CCW converters on the driver breakout board. I'll use a separate Microchip PIC processor for each axis to do this. I could use discrete logic to do this but I also want to use the PIC to improve the homing accuracy.
The Vextra drives (1/2 steppers) have a sync output that is present every 20 steps. I plan to AND this with the home switch input before sending it to Mach3.
This will improve the repeatability of the home switches, as once the switch is activated, the axis will continue to move until the drive activates the sync signal. So even though the activation of the optical home switch will have some variability, it will be corrected by the sync output which is absolute. I used this technique on my TurboTaig board and it works very well.