DIY Router Power Control Question

[ignatz]

Hi Everyone, I am considering building a small circuit to control the on/off state of a router on my CNC machine. The best schematic I've been able to find so far is here (The Optoisolated high power control circuit)

I have the HobbyCNC 4UAPC kit and know that it has pinouts for Parellel port pins that I can use to control the circuit.

Has anyone else built there own relay board? Do you have any suggestions?
Will the schematic above work?
Is the Optoisolation necessary? A good idea?
Is there a better open source plan available?

While searching for information here, I ran across references to DigiSpeed . Can this be used to control any spindle (like a Router or RotoZip) or is it only for the Sherline spindles?

Thanks in advance.

[sol]

Similar to the circuit you linked to but simpler. Takes advantage of the FET 2N7000 whose virtues are lauded in post #21 of the following thread.

http://www.cnczone.com/forums/showth...020&#post38020

[pminmo]

My two cents, never use a mechnical contact relay to turn an inductive load on and off within yards of electrical wiring that attaches to computer logic. Why, because mechanical contacts bounce, i.e. quick open and closes (milliseconds) before the settle into the open or closed state. When you couple the bounce with inductive loads and 120vac, you spray electrical interference into anything conductive. You periodically see it posted as:
Why when I turn off my .... my computer hangs, or
why when I turn on my ... my drivers hang or reset or......

The solution is SOO easy and painless zero crossing optically isolated solid state relays: such as:
http://www.futurlec.com/RelSS.shtml
or
http://www.mpja.com/listitems.asp?dept=133&main=132

You will probably still have to use a driver (FET or Darlington transistor) to interface to the pc, just as you would a relay as most take a little higher current than the pc PPT can source or sink. A mechanical relay that is switching currents has no business anywhere near wiring to a pc parallel port, or stepper motor drivers.

Phil

[ViperTX]

DigiSpeed is a DC motor controller, not an AC motor controller.

[ignatz]

sol - Thanks for the link and the info. Did you actually build the circuit? If so, how does it work for you? Did you worry with Opto-Isolation between the FETlington and the Parellel Port?

pminmo - I had no idea... thanks very much. Just so I understand correctly, you're suggesting that I could simply replace the Relay in either schematic with one of the ones you've listed? Does the Opto-Isolation cicuit in the link I posted prevent the interference you mentioned or should that feature be built into both places?

ViperTX - I knew I was missing something.... Thanks. Do you know of an AC speed control esp. one that works with DigiSpeed in TurboCNC?

[pminmo]

Here is an example:

Phil

[Al_The_Man]

Originally Posted by pminmo Here is an example:

If a 2N7000 was used it does not impose any load on the parallel port, due to being a voltage rather than current operated device.

The DigiSpeed refers to controlling a KBIC-120 which in turn says it will control permanent magnet DC motors as well as Universal AC/DC motors, these are most commonly used in routers and hand tools etc.
You cannot use it to control a normal AC induction motor.
Al.

[sol]

Originally Posted by ignatz sol - Did you actually build the circuit? If so, how does it work for you? Did you worry with Opto-Isolation between the FETlington and the Parellel Port?

Yes, built two: One for the Router spindle and one for the Vacuum.
No isolation, just the FETs, so far so good but were I building it again I'd use the relays Phil linked to for peace of mind...Still use the FETs though. They have turned out to be an extremely handy component to have around. Every time I pull one out of the bin I think "Thanks Al The Man!" since his posts here introduced me to them.