What would you do?

[cnczone]

I am designing some attachment pieces for a 3 axis CNC machine. But, I would like your advice at to what you would do. I am completely new to this, so I don't know all the electronic components I should be considering.

Without going into to much confusing detail, I have a situation where I have 60 small plastic cups lined up next to each other. Each cup holds small 1/2 inch wooden "blocks" (for lack of a better description). The cups are held by/hanging from a shelf where the bottom of the cup is exposed and cut open (an opening) and covered by a thin metal "gate" /hatch that I figure will be opened or closed by a solenoid (?).

My question is this. If I am going to use the parallel port of my computer to control the 3 axis stepper motors - how can I be able to utilize the remaining pins/outputs in my breakout board/driver to control the turning on/off of 60 relays to the solenoids? That is, I don't have 60+ output pins in a parallel port to be able to physically hardwire 60 different different relays to solenoids (as well as the stepper motors). The way I "think" I need to do this is to only use 2 or 3 of the outputs to send a "code" signal to some circuit that will understand which relay should be powered on, based on that "code" signal. The question is, is my thinking correct? And if so, what kind of hardware is involved? From what I could see on the internet, I think I need to use something called a PLA (Programmable Array Logic). Is that correct? If so, does anyone have any links to plans and/or can tell me the formal name of the kind of circuit I am envisioning here? Also, do I need to have relays involved (think I do, as I think a relay is a switch thingy - but isn't a mosfet also a switch - which is better)? I do plan to have another power source that all these 60 solenoids would be connected to, so don't worry too much about the power part of it. Also, I am a programmer, so don't worry too much about the coding part/actuating signals out from the parallel port part of it. Thanks.

[ger21]

Are you using Mach3 to control it? Or something else?

I could be wrong, but I'm not sure if you can somehow use 2 outputs to control 60 devices. Although thinking while typing, I guess you can use 3 outputs to get 1000 code combinations, so maybe it is possible. But you'd need to use some type of external hardware (PLC?) to "decode" the state of the 3 outputs and do the desired action. Mach3 can control PLC's via Modbus.

Mach3 can also use an I/O device, like the Pokeys, that will give you 55 outputs.
http://www.poscope.com/product.php?pid=3

I think that how you open or close your "gate" may dictate the method used to control them.

Sorry, but I can't give you a more specific answer.

[Al_The_Man]

I would visualize it 2 ways.
If you have to index the stepper motor between solenoid operations, you could use a trigger pulse, or Binary coded signal to a PLC (Programmable Logic Controller).
Say you have to index the stepper 60 steps, after the first index a trigger pulse could be output to the PLC when the solenoid operation is completed an input to the PC would tell the stepper to index again, if 60 signals are needed, you would need 6 outputs.
You could also make up the logic with a PLD or even a PicMicro, but the PLC has the advantage of already having relay or SSR outputs and conditioned inputs.
Al.

[keebler303]

I'm not sure if it is supported yet, but the smooth stepper has an SPI expansion port which could be used to talk to an MCU or PLC.

You could use coded binary, 6 outputs for the 3 axes and 6 outputs for the solenoid control circuit would give you 63 "outputs" and would fit on one parallel port. This is limited though in that you can only have one on at a time, unless you have some more logic outside the computer besides just decoding the binary signal. It may also work to make up your own 6 bit parallel protocol which you could use to send multiple 6 bit bytes. 63 (111111) could be the start byte, to tell the micro to pay attention, then it would store the data bytes until it got a 63 again, which would signal the end of the command. This could be pretty versatile if you could get the timing worked out so it functions properly.

Matt

[cnczone]

Thanks everyone for the ideas. I will start looking into them. Currently, I think I am liking the idea of using this: http://www.poscope.com/product.php?pid=3. I didn't really think too much about USB before because most of the solutions I found earlier online for the 3-axis part of my CNC project were parallel port solutions. I saw one or two things for USB, but they did not seem so complete. But, this item seems like it is very open ended and gives me a bunch of possibilities.

I don't know what software I will be using of if I will just write my own software. I looked into Mach 3 and that is what everyone else seems to be using, so I might go with that. We will see.

[Al_The_Man]

Without knowing the full details of what you want to do it is difficult to give a specific answer, for example, if the operation only needs limited operator input, i.e. no G-code programming etc, and the operation is repetitive point to point, then you may not need CNC type controller, in that case a stand alone answer may suffice.
You can operate a PLC with stepper outputs and simple operator interface such as Maple display etc.
No PC or Mach required.
Al.