Building a positioning visual display.
I am in the process of building an OSD for my home built CNC machine.
The circuit utilises CD40110BE up/down/counter/drivers directly driving dual 7 segment displays. The ICs have an up input and down input together with a reset. The ICs are cascaded and a signal at the first IC will increment up and down and to each of the other ICs in turn.
I have already built the circuit boards and am in the process of populating them. The complete project can be seen using the free version of CircuitMaker which I have found to be the best programme that i have come across for building circuits. The project is called 'CNC OSD' and anyway is free to use it or modify it as they see fit.
It is my intention to use the pulses from the BOB to the stepper drivers to increment and decrement the count on the OSD by using a microprocessor to send the pulses after first taking account of the microsteps for a given linear movement. I also intend to incorporate a handheld 'jogging' control
But, my problem is where is the best place to pick up the pulses from the BOB.
First of all, does anyone know whether the BOB sends a 'PULSE' and 'DIR' pulse simultaneously to reverse motion or just a 'DiR' pulse? Secondly; I am working on the jogger to send pulses back to the BOB using a variable speed oscillator (fast and slow) to provide the necessary pulses to move the machine backwards and forwards. Where is the best place to connect to the BOB that will not cause problems for the normal BOB output to the stepper drivers.
I am about to change my BOB for this one: https://www.ebay.co.uk/itm/5-axis-CN...kAAOSw4CFY3L55 and the system will be controlled from Mach3.
Any help would be appreciated especially from someone familiar with microprocessor control. I do not have any microprocessor experience and intend to use a Genie unit because it can be programmed through a flowchart system but any help with Arduino or similar would be a great help.
Re: Building a positioning visual display.
The BOB doesn't create the STEP/DIR signals. They are created by Mach3. All the BOB does is make them more accessible, and add some isolation, than you wiring directly to the parallel port plug. The relative timing of STEP and DIR signals should be configurable in Mach3.
You may need to experiment to see where you can pull out the signals. If the parallel port has the drive strength, you might want your step display board between the port and the BOB.
If you wish to inject your own signals, you must do it in such a way as to not drive signals backwards into the parallel port. For example, if the port is driving a signal low and you force it high, there may well be an incidence of magic smoke emission. Then you will emit some swear words, followed by an emission of money as you buy a replacement computer. Some logic gates would allow your extra signals to be combined with the parallel port signals, with the added bonus of giving stronger signals that your display could read.
So overall, the computer parallel port and your signal generator would feed into some sort of combiner or multiplexer, which would in turn feed both the BOB and your display module.
The signal combiner or multiplexer part is not immediately obvious. An OR gate seems like an obvious candidate but fails if, for example, Mach3 leaves a DIR pin HIGH when you wish to jog in the DIR pin LOW direction.
Re: Building a positioning visual display.
Quote:
Originally Posted by
vegipete
The BOB doesn't create the STEP/DIR signals. They are created by Mach3. All the BOB does is make them more accessible, and add some isolation, than you wiring directly to the parallel port plug. The relative timing of STEP and DIR signals should be configurable in Mach3.
You may need to experiment to see where you can pull out the signals. If the parallel port has the drive strength, you might want your step display board between the port and the BOB.
If you wish to inject your own signals, you must do it in such a way as to not drive signals backwards into the parallel port. For example, if the port is driving a signal low and you force it high, there may well be an incidence of magic smoke emission. Then you will emit some swear words, followed by an emission of money as you buy a replacement computer. Some logic gates would allow your extra signals to be combined with the parallel port signals, with the added bonus of giving stronger signals that your display could read.
So overall, the computer parallel port and your signal generator would feed into some sort of combiner or multiplexer, which would in turn feed both the BOB and your display module.
The signal combiner or multiplexer part is not immediately obvious. An OR gate seems like an obvious candidate but fails if, for example, Mach3 leaves a DIR pin HIGH when you wish to jog in the DIR pin LOW direction.
Thank you for your reply Pete and I note what you say about taking the pulse and direction signals from the parallel port.
In my new build, I shall be incorporating a UC100 USB to parallel converter to provide compatibility with later PCs and also be able to use a slower PC as the UC100 buffers and takes care of the signals to the parallel port.
In my old configuration, I used a cheap Chinese BOB daisy chained from a simpler straight through version that had optical isolators on it If I were to use that same isolating board with the new BOB, would that not prevent unwanted signals being fed back to the PC? If that were so, then the 5V supply to the isolators should also be useful to carry the required current for the pulses should it not?
If I go that route, I cannot see how the positioning on the PC screen can be updated along with the 'jogging' signals that I generate. Is there some form of feedback to the PC as my old board had facility for a handheld jogger which I never used and do not know whether it fed back or not.
Re: Building a positioning visual display.
The opto-isolators should protect the parallel port but there is still the problem of conflicting signals coming from the port and the handheld jogger.
There must be some one who makes a thing-ee that turns an MPG (manual pulse generator, the jogger) into a USB keyboard equivalent device...
Cool, I just googled "USB MPG" and lots of neat options appeared.
