Re: port problem

Terry,

No, I'm afraid that won't do. Connected this way, you are trying to
source current to drive the SS relay. The '374 latch IC (or whatever
part they're using) will only supply a few mills of current in this
mode. You'll have better luck if you connect pin 1 of the port to a
2.2K resistor, the resistor to the base of a NPN transistor say a
2N3904, or 2N2222. the collector goes to the (-) of the SS relay, and
the emitter goes to ground. The (+) of the relay goes to about 12v.
when pin 1 is low, the transistor is off, the relay is off. When pin 1
goes hi, the transistor conducts, and the relay goes on. This should
get you started.

Alan

Terry Ackland wrote:

>
> --- Alan,
> thanks for the response. I just connected pin 1 of the port to the
> plus of the relay and the minus on the relay to pin 18 of the port.
> No good?
> Terry
> In CAD_CAM_EDM_DRO@egroups.com, Alan Marconett KM6VV <KM6VV@a...>
> wrote:
> > Terry,
> >
> > I don't know how you're wiring the SSrelay, but you might just need
> an
> > open collector transistor to drive the SS relay. Most parallel
> ports
> > can SINK more current then they can SOURCE. Are you using the
> "active
> > low" level to drive the SS?
> >
> > Alan
> >
> > Terry Ackland wrote:
> > >
> > > Guys,
> > > I have finally got around to connection up the recommended relay
> > > (CX240D5) to my parallel port and a spindle but I am not having
> any
> > > luck.
> > > I can turn the 5 volts on and off using M-codes but there does not
> > > seem to be enough current to operate the relay. It was mentioned
> in a
> > > previous post that a new parallel port board would be needed if
> there
> > > was not enough current available. Would someone advise me on the
> > > particular board and what should I ask for when ordering one? I am
> > > using an old 386 which is fast enough for what I need.
> > > I also have a backup 386 that I picked out of the garbage, it
> works
> > > fine but the pins switched by M-codes are always on even when
> > > instructed to turn off so I think 2 boards are should be ordered?
> > > Thanks, Terry Ackland
> > >
>