Re: [CAD_CAM_EDM_DRO] cable shielding and relays

In a message dated 2/26/2003 12:40:49 PM Central Standard Time,
mrpootoo@... writes:

> 2. Does anyone have a source for a safe (to my equipment), simple to
> make or premade relay setup for turning on spindles, etc.?

International Rectifier ("IR") Crydom Solid State Relays are wonderful for
switching-on 120-480 VAC stuff. They are available in 120, 240, and 480
voltage versions, and maybe more I don't know about, and in current-handling
ratings from 10 amps, 20, and maybe higher? in the industry-standard
rectangular shape/size.

The "isolation" between the input-terminals and the output (switch-)
terminals in "infinite" (thousands of volts), and they also come in DC and AC
input-versions. The DC-in versions switch on at 3 volts, on up to 32 VDC, I
think it is, and the AC-in versions take 90 to 280 VAC in (at a very few
mA!). There are competing brands "just as good". I have no experience with
those, however.

ALL the three-phase woodworking machines in my home-shop have three-each of
the AC-versions, to effect "automatic-off if power-drop-out" "contactors".
(if power fails for ONE AC-cycle, relays go off and stay off until START is
pressed again). Some States require this (not here! Texans know to "check
first" before finger-pokin' !)

The 240 VAC spindle-motors on my two little home-brew CNC lathes (3-phase,
1/2 hp) are switched by three-each of these, with input from bit-8 of the
parallel-printer-port of the controlling PC.

TRY 'em! You'll LIKE 'em! Jan Rowland


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