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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subjects, that are not allowed on the CCED list.
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