Re: [CAD_CAM_EDM_DRO] Re: Pixie error connection

Hello Keith,
Hello Keith,

I looked at the Pixie specs at
http://www.skyko.com/datasheets/SKY-P100.pdf . The paragraph on errors
says that the error signal is pulled up to +5v with a 5kohm resistor. It
does not mention current specifically but I can make some good guesses.

A 5kohm resistor to +5v can source 1ma.

The spec says that multiple Pixie errors can be wired together. This
means that the open collector at any one of the error pins must be able
to sink the total current from all of the error pullup resistors. I
don't know how many Pixie boards are permitted but I would guess that a
six axis machine is not out of the question. That would mean that the
open collector should sink at least 6ma.

As for the relay, I only found data on the Dayton 5Z950 solid state
relay at the Grainger website. Is that a Grainger house brand?

The Grainger spec gives voltage range for the control input but gives no
info on control current or resistance. So I have no idea what current is
needed to activate the relay. Could be a couple of ma or could be 100ma.
Gotta get the info from the vendor or the manufacturer or you need to
test it yourself.

You can connect three 1.5v batteries in series with the control input
and measure the current, assuming the relay activates. If that works,
try a potentiometer in series with the batteries and control input. When
the pot is at max resistance the relay should be off. If not, then you
need a larger resistance pot. Then adjust the pot for less resistance
until the relay activates. Note the current. The open collector input
must be able to sink more then this current.

If the relay input requires more current than the open collector can
sink then you can do one of two things.

1) get a more sensitive relay so that the input requires less current
than the open collector can sink. Look for relays that say that their
inputs are TTL compatible. And be sure to determine the turn-on current
requirement.

2) add a transistor to increase the current to the relay. I would use a
PNP transistor with collector current capability more than the current
required by the relay. Probably something similar in performance to a
2N2222. But the 2N2222 is an NPN transistor. I think the 2N2906 or
2N2907 is a PNP. I doubt that you need a Darlington PNP transistor but
it should work too.

Wiring for a PNP transistor:
The Pixie +5vdc goes to the relay positive control.
The relay negative control goes to the transistor emitter.
The transistor collector goes to the Pixie 0v.
The transistor base goes to the Pixie open collector.

Tom Hubin
thubin@...

************************

toolspindoctor wrote:

>
> Tom,
>
> Thanks! I am trying to find out about the specs on the Pixie but have
> none at this point. I did have the same source for the +5v for the
> Pixie and the relay.
>
> Keith
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Tom Hubin <thubin@...> wrote:
> >
> > Hello Keith,
> >
> > > I gave it a try and connected +5v to the + of the relay
> >
> > The +5v needs to come from the pixie too. Is that where you got it?
> >
> > If you are using +5v that is not from the pixie then you may need to
> tie
> > the +5v power supply ground to the pixie ground.
> >
> > Can you point me to data sheets for the pixie open collectors and
> for
> > your solid state relay control? If I can determine the capability of
> the
> > open collector and the pixie connector pinout and the requirements
> for
> > the solid state relay, I should be able to make a more specific
> > recommendation.
> >
> > Tom Hubin
> > thubin@...
> >
> > *************************
> >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler"
> <grezmos@>
> > > wrote:
> > > >
> > > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "toolspindoctor"
> > > > <clarkfamily5@> wrote:
> > > > >
> > > > > Graham,
> > > > >
> > > > > I am trying to drive a Dayton Solid State Relay, Input DC,
> Maximum
> > > > > Input Voltage 32 VDC, Minimum Input Voltage 3.5 VDC, Output
> DC,
> > > > > Minimum Output Voltage 0 VDC Grainger part #5Z950. Probably
> too
> > > much
> > > > > draw and it drops the Pixie to 0volts each time I connect.
> Must be
> > > a
> > > > > way to place a resistor...
> > > > >
> > > > > Thanks,
> > > > > Keith
> > > >
> > > > In mentions opto coupling so am I right that the "coil" has a
> > > polarity?
> > > >
> > > > If so connect the + to 5v and the negative to the pixie. That
> way
> > > > when the pixie pulls the output low the led in the opto will be
> > > energized.
> > > >
> > > > Connecting the relay the other way will tend to pull the pixie
> down
> > > to
> > > > ground and cause the fault.
> > > >
> > > > Please apply a pinch of salt as I have not used SS relays but I
> > > think
> > > > I am right.
> > > >
> > > > Graham
> > > >
> > >
> > >
> >
>
>