Re: [CAD_CAM_EDM_DRO] Re: Wiring Soundlogic/Campbelldesigns Breakout Board

On Sun, 04 Jan 2004 17:04:46 -0000, you wrote:

>Bob:
>
>I got mine in the mail yesterday, and it is great.
>
>I do some questions about the gecko and relay hookup:
>- Step 17 directs "connect the G. drives according to the
>G.installation sheet..." That's Mariss's sheet, correct? That would
>mean setting the pin array for +5?
>
>- For the relay switch: I'm planning to use a 15 amp router, 110 ac
>voltage, for my spindle. I'm inclined to use a mechanical relay,
>thinking it might be safer. Most wiring diagrams advise using a diode
>to guard against voltage spikes in the relay circuit. Does the card
>provide this protection ?

I have no idea what's on the card, but I'd personally be tempted to
put a 400 to 600 PIV diode (1-3 amps rule of thumb) across the relay
coil IF it is a DC coil. You wire the diode so that the coil plus
goes to the cathode, back biasing the diode under normal operation.
When the relay coil is de-energized, the magnetic field induces a
reverse polarity spike. It's that spike that damages the electronics
(because it is often higher than the supplied voltage, let alone the
wrong polarity). The diode will conduct and short out this spike,
protecting the electronics.

Even if they have a diode on there, I'd consider this a failsafe as
well. BTW: this needs to be done on all sorts of relays, regardless
of voltage and coil rating *unless* they are AC. Best you can do on
AC is a zero point switch to the coil or an MOV.

Harvey

>
>Thanks for your time.
>
>Tom
>
>
>