Spindle Control Circuit?

[boguski.1]

Hi to all,

My apologies for not posting until now, I am a student and still absorbing information for my first machine design!

I have purchased the Xylotex 3-axis kit with 425oz steppers, and am almost done building my control box. I am confused as to how to go about controlling the router (will be either a 2.25 or 3hp porter cable) with a relay. I have a Crydom smr2425, 25A. I've seen diagrams with mosfet (spelling?) circuits as well as a circuit that goes from +5V through a resistor to relay positive, then out relay negative to pin 16. I don't want to fry my motherboard! Does anyone have any suggestions for a simple relay circuit for my situation? One other issue, despite the description in ebay that stated my relay was 3-32V DC control, it is actually 8-32V DC control. Would it be safe to use an 8 or 9V DC wall wort for my limit/home circuits as well as my relay circuit? I am worried that the parallel port will not be able to handle the additional voltage, though I really have no idea.

I have attached my wiring diagram (not yet complete) which shows what I have so far. It is an AutoCAD file; if someone knows an effective way of posting these as images that do not distort I would be interested to know! Electricity is somewhat of a mystery to me, but I can follow basic circuitry and solder. Thanks!

I guess I'll include a disclaimer as well: By no means does this wiring diagram in any way shape or form portray a tested, proven circuit, use at own risk as it is a work in progress!


Brian

[Al_The_Man]

If you want to control a load from the Parallel port, then you need a buffer and also in your case isolation for the router, search forums here for 2n7000, it will explain it, you can use this cheap transistor for a buffer and you can also use up to 36vdc to switch a SSR (solid state relay) for the Router.
Al.

[toneV8]

Al_The_Man: Where is used solid state relay. I have two OPTO 22 ZS24D10
240VAC, 10Amp, DC control, Signal Pick-up Voltage 3VDC ( 32V allowed )....

[Al_The_Man]

With those SSR's you could control any AC load that is rated up to 10amps, such as spindle motors or solenoids etc.
As I mentioned, if using parallel port to switch the low voltage input, you should use a buffer transistor of some sort.
Al.

[boguski.1]

Thanks Al, I'll research the transistors and see what I can come up with.

Would it be safe to use 9V as opposed to the standard 5V that is typically used for limit/home circuits? With limited knowledge on parallel ports, I am worried that the added voltage may cause problems with the port, though I suspect this is more of a current issue than a voltage issue.

I guess my main question is what is the maximum voltage and or current that a computer parallel port can sink safely through one of these circuits?

Brian

[Al_The_Man]

With the transistor I suggested, anything up to 60vdc is possible, the 2N7000 is a 'Fetlington' Darlington/FET combination, Only the FET gate and common is connected to the port, which is very high impedance (no current).
The FET Source pin and the Port common are connected together, the DC voltage connected to the FET load via the FET Drain pin can be 12vdc from the computer if you wish, or another source up to 60v. In the case of the PC 12v the common is already connected, but if you provide another source, like 9vdc then the common of this is connected to the common of the port.
There is several circuits examples here in the Forums.
Al.

[boguski.1]

Al,

Here's a rough schematic of what I think will work based on your input. I've included a limit switch in the diagram as well. Please let me know if this is right!

Also, I was hoping you could enlighten me on the role of the diode in the circuit, and if it is even necessary for a SSR. If it is needed, what specification should I be looking for when purchasing?

Thanks for all the help, I'm very close to understanding this circuit!

Brian

[Al_The_Man]

You only need the diode on magnetic relays, I don't think the parallel port will take kindly to inputing 9vdc.
If you use the 5v supply from one of the PC hard drive connectors for the limits, it will be common to the port.
Al.

[boguski.1]

I solved my problem! I just purchased a relay that has 3-32V DC control instead of the 8-32V one. I will now be able to use the VCC terminal on the Xylotex board that puts out +5V for my limit, home, and relay circuits.

A quick hint for anyone else working on this area of the electrical system: get your meter out and check stuff! I was under the impression that the +5V came from the parallel port, but with the port disconnected the board puts out the required voltage for the circuit. Hopefully now I won't have to use a wall wort.

I have attached an updated schematic that should be correct based on this new information (well new to me anyways!) Thanks for the help.

Brian

[eloid]

off pin 10 on you diagram the 3 lim switches are they x,y,z ? are these new switchs or same as cnc limits switchs machine?

[boguski.1]

The limit switches in the diagram are merely representative of limit switches wired normally closed in series. The home switches are wired on separate pins, since the software needs to know when each axis reaches home individually. My machine is going to have 2 limits per axis, as well as two emergency stop buttons (one on the control box and one on the machine) that are all wired in series to pin 10. Wiring in series normally closed is a safety precaution; any wiring fault (or tripped switch) in the circuit (regardless of its axis) will trigger a limit response in the software, forcing the operator to either check the wiring or jog the machine until the limit is closed. Hope this answered your question!

Brian