Re: [CAD_CAM_EDM_DRO] Getting Parallel port to run relay

Ahhhhh

Still learnin

Thanks

Scott L Golden
Never Give Up

>
> A fuse, (assuming that it was fast and sensitive enough to blow before the
> transistor or p-port output were damaged), would have to be replaced every
> time you turned the relay off. This would get very tiring very soon...:)
>
> Yes, the "one-way choke" is called a reverse-biased diode. When the

control

> circuit supplies voltage to turn on the relay, the diode does not conduct,
> when the control circuit turns off, and the collapsing field in the coil
> generates the large reverse voltage, the diode conducts, and shunts the
> voltage away from the transistor.
>
> Andy Wander
> Verrex Corporation
>
> -----Original Message-----
> From: Scott L Golden [mailto:escowizard@...]
> Sent: Friday, January 28, 2005 8:48 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Getting Parallel port to run relay
>
>
> I may be way out on a limb here but can't one put fuses in line? I admit

low

> amp fuses but wouldn't that help with spikes?
>
> Now go easy on me... I am not too deep into electronics.
>
> Or isnt there a one way choke or something to limit the flow of power
> backwards?
>
> Sorry for the lack of knowledge but....my thoughts anyway. lol
>
> Scott L Golden
> Never Give Up
>
>
>
> ----- Original Message -----
> From: "Andy Wander" <awander@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Friday, January 28, 2005 3:27 PM
> Subject: RE: [CAD_CAM_EDM_DRO] Getting Parallel port to run relay
>
>
> >
> > Alan:
> >
> > I'm talking about the huge inductive "spike" that occurs when the
> "control",
> > whether it is a switch, a parallel port pin, or whatever, opens the
> circuit.
> > This causes a voltage spike that WILL fry transistors!
> >
> > But the OP has indicated that he DID have a suppression diode installed
> > across the coil, so that is probably not the problem.
> >
> >
> > And it is very possible to control relays with the parallel port

directly;

> > I'm controlling some small 5V relays directly with my parallel port. You
> > just nned to make sure that the relays source less current than the port
> can
> > sink(low-active is recommended).
> >
> >
> >
> > Andy Wander
> > Verrex Corporation
> >
> > -----Original Message-----
> > From: Alan Marconett [mailto:KM6VV@...]
> > Sent: Friday, January 28, 2005 3:02 PM
> > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subject: Re: [CAD_CAM_EDM_DRO] Getting Parallel port to run relay
> >
> >
> > Hi Bert, Andy, list,
> >
> > After thinking about it, I wonder if simply connecting a parallel port
> > output pin to a relay coil would damage it. It wouldn't work, mind you,
> > but relay coil will still offer some resistance, and the current flow
> > will be limited. If the other end of the coil is grounded, then a HI on
> > the pin will typically have minimal source capability. If the other end
> > of the relay is connected to +5, then the pin will try to source
> > probably 20-30 ma. What was the voltage/current rating of the relay
> > coil? Provided the coil was not not left "energized" for a long
> > period, no damage may have been done. Give it a check with an LED and a
> > 220 ohm resistor!
> >
> > Alan KM6VV
> >
> >
> > Andy Wander wrote:
> >
> > > If you hooked a relay up to your parallel port, and you didn't install

a

> > > diode or other suppression device in parallel with the relay coil,

then

> > you
> > > may have fried your printer port pin. When a coil has a field set up

in

> > > it(by having current flow through it), opening a contact(your port

pin)

> > > stops the current flow and causes the field to collapse, generating a
> > large
> > > reverse current through(and hence a reverse voltage across) the coil.

If

> > not
> > > shorted through some sort of snubber circuit(I use a reverse-biased
> diode)
> > > this can cause switch contacts to arc, and can also blow out

transistor

> > > circuitry.
> > >
> > > This is the same principle used to generate high spark plug voltages
> using
> > a
> > > DC battery in your car(ok, I know the new cars may use a different
> method,
> > > but this is the traditional methed)
> > >
> > > Andy Wander
> > > Verrex Corporation
> > >
> > >
> > > -----Original Message-----
> > > From: bertmantx [mailto:bertmantx@...]
> > > Sent: Thursday, January 27, 2005 10:06 PM
> > > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > > Subject: [CAD_CAM_EDM_DRO] Getting Parallel port to run relay
> > >
> > >
> > >
> > > Looking for any advice an how to get parallel port to activate relay
> > > to start plasma torch. Inatalled PC relay (which I now know to mean
> > > Printed Circuit) and tried running it direct from parallel out put.
> > > All was well for about 20 cuts and then it just stayed on. If it is
> > > off when hooked up will stay off until turned on then stays on. Have
> > > tried hooking NPN xsistor with Game port 1 to coil, coil to
> > > collector and emitter to ground. 1K resistor between parallel signal
> > > and Base. No response when hot signal (verified +5.9v) touched to
> > > resistor or direct to base of xsistor. If shorted from collector to
> > > base will trip 20 or so times then nothing. Remaining Para ports are
> > > running motors fine.
> > >
> > > Any thoughts on damage to computer?
> > >
> > > Any pointers on assessing computer damage?
> > >
> > > Hard to believe there isn't a plug and play device just for this,
> > > but have had no luck finding anything.
> > >
> > > First cuts looked surprisingly good and had High hopes. Depression
> > > is now setting in quickly.
> > >
> > > Any advice greatly appreciated.
> > >
> >
> >
> >
> >
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> > http://www.metalworking.com/news_servers.html
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> > http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
> sister site to the CCED group, as many of the same members are there, for

OT

> subjects, that are not allowed on the CCED list.
> >
> > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
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if

> you have trouble.
> http://www.metalworking.com/news_servers.html
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> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
> sister site to the CCED group, as many of the same members are there, for

OT

> subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
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> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
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> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:

aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.

> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a

sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.

>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.

DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........

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