RE: [CAD_CAM_EDM_DRO] SS Relays

> From: Jack Hoffa
>
> Help!
> Non_Electrical guy needs advice for specific types and Where to get
> SSR's for Spindle motor on-Off, Flood and mist control, etc.
>
> Thanks so very much
> Jack Hoffa

Hi Jack,

I asked a very similar question on 10/31. So that folks don't have to send
them again below are the messages that I got back ...

Cheers,

Chuck Hackett
"Good judgment comes from experience, experience comes from bad judgment"
7.5" gauge Union Pacific Northern (4-8-4) 844

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> From: David A. Frantz
>
> Hi Chuck;
>
> Its pretty hard to reccommend a specifc relay as there are anumber of
> considerations to take into account. One good source, for a very
> large number of SSRs, is Newark Electronics. It is also a good idea
> to checkout your local electronics / industrial automation
> supply houses.
>
> NOt all SSR's are zero croussing so do keep that in mind.
> Personally; for things like coollant and other motor loads, you would
> probally be just as well off to go with a mechanical relay. If the
> motor is of any size at all you really should have a motor starter
> installed. The NEC will define exactly when and where a motor starter
> is required.
>
> As far as all of the other loads it is a mixed bag. For marginal
> loads, it is hard to beat the OPTO 22 format for flexiablity, on the
> other hand PC Boards with a bunch of optical isolators can be much
> cheaper if your working with only one driven voltage.
>
> Thanks
> dave

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> From: JanRwl@...
>
> Chuck:
>
> I am surely not even AMONG the first to respond to this question, but I

can

> say something: I have used IR Crydom SSR's for years, where I need to

start

> motors or turn-on 100+W. lamps, etc., from "TTL" and low-DC

signal-sources, and

> have had PERFECT luck, except for a few that IR had subcontracted to a
> south-of-the-border subcontractor, which would NOT hold up when expected

to operate a

> motor-load, even of only half the amp/voltage rating had been asked of

them.

> More recent ones (different colors and pattern on the logo-sticker on the
> front of the things!) seem vastly more reliable. So goes it, sometimes,

when

> fiscal wisdom is suffering THD, etc.
>
> Did you say "inexpensive"??? Unless you don't figure-in replacement-part
> costs and the value of your TIME to swap-out junk gone bad, the LEAST

expensive

> way to build stuff is to use the BEST components you can possibly afford

from

> the outset! I'd much rather spend $30 for an SSR that keeps on working,

than

> $8.95 for one that needs to be replaced in six weeks, out in the rain!
>
> Lotsa luck! Jan Rowland

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> From: Jon Elson
>
> Egroupscdh (E-mail) wrote:
>
> >Can anyone recommend a source for inexpensive (but reasonable quality)

Solid

> >State Relays (SSR) to use between the Ahha driver box and things like

coolant, etc?

> >
> >Is there a real difference between these SSRs? I.e.: Do all of them do
> >their switching at the zero crossover to minimize noise? Is this a real
> >concern? All of my components (PC, Ahha driver box, VFD, etc. will be
> >mounted in the rear cabinet of a Bridgeport Series I conversion.
> >
> >
> Crydom has some really cheap epoxy-dipped units that are available from
> Digi-Key or Mouser. The Crydom part # is D2W202F, it is good for 240 V
> and 2 A. If more current is needed, I use an external contactor.
>
> Jon

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> From: Mark Thompson
>
> Hi
>
> www.digikey.com is a great place to get most anything electronic.
>
> Most relays that are zero crossing are AC only (IE: Triac based). So if

you are

> trying to switch a DC source the AC type SSR will turn it on but not turn

it off.

>
> You will find that SSR are typically very expensive relative to there

mechanical

> counter parts.
>
> On the other hand it takes quite a bit more to drive a mechanical relay,

so it a

> trade off.
>
> For most low load needs a mechanical relay will do the job fine.
> Note: Put a small .1uf (500v) capacitor across the load leads to minimize
> arcing on the contacts.
>
> Good luck.
> Mark

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