PLC's - was Re: IGBT long life at 3X rated Ip?? Re: 15kva 14.4 kV Transformer.. (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sun, 24 Dec 2006 16:46:22 -0800 (PST)
From: Yurtle Turtle <yurtle_t@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: PLC's - was Re: IGBT long life at 3X rated Ip??  Re: 15kva 14.4 kV 
    Transformer.. (fwd)

We use Allen Bradley PLC-5's at work. Way overkill for
a Tesla coil. While I agree that "you get what you pay
for", most folks can do everything they need with
simple relay logic. I'd love to hook up a PLC to mine
with a fancy HMI with cool graphics, but I can't
justify the cost. I just don't have enough I/O. I also
have a knack for blowing things up. I'll bet most
folks who use PLC's on their coils either have deep
pockets, or have access to cheap or free used PLC's.

Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Moderated and approved by: Gerry Reynolds
> <greynolds@xxxxxxxxxx>
> 
> 
> 
> ---------- Forwarded message ----------
> Date: Sun, 24 Dec 2006 17:12:20 EST
> From: FIFTYGUY@xxxxxxx
> To: tesla@xxxxxxxxxx
> Subject: Re: IGBT long life at 3X rated Ip??  Re:
> 15kva 14.4 kV  Transformer..
>     (fwd)
> 
>  
> In a message dated 12/24/06 12:14:40 P.M. Eastern
> Standard Time,  
> tesla@xxxxxxxxxx writes:
>  
> >Automation Direct has a large selection of PLC
> controllers --- some under  
> 
> >$200.   These work great for control  applications.
> 
> 
>  
>     Not to rain on D.C.'s post, but I work with a 
> variety of PLC's every day 
> as my job - very common in industrial  machinery.
>  
>     The Automation Direct PLC's are made by Koyo. In
> my  experience with 
> their modular PLC's:
>  
>     1) Power supplies fail. Some sort of bad solder 
> joint problems. But I've 
> had problems with *all five* of the ones I've ever 
> dealt with, and they were 
> of different ratings. They might last a few  years,
> but eventually they will 
> die. And as they mate into the PLC modular  rack,
> they are proprietary. 
>  
>     2) Software/capabilities are a bit weak compared
> to  the other industry 
> standard PLC's. Timer values are limited,
> inputs/outputs  assignment are 
> limited and somewhat idiosyncratic. Just makes
> things more of a  pain to casually 
> play with them.
>  
>     3) I've had one of their "com interface" modules
>  die (the thing that 
> allows connection between the programming PC and the
>  PLC).
>  
>     4) Tech support is iffy quality.
>  
>     You get what you pay for. While I'm sure 
> Automation Direct must have 
> some decent deals, I never found them to  be worth
> the gamble for any components 
> I was willing to install in machinery I  was tasked
> with building/maintaining. 
>     FWIW, I'd go with either a Siemens or
> Allen-Bradley  micro PLC. Siemens 
> has micros that are incredibly compact and powerful,
> and they  love to *give* 
> you all the support and software you need.
> Allen-Bradley has the  better 
> programming software, but they are very "snooty"
> about tech support  unless you've 
> *bought* a support package.
>     Just be careful about running too much current 
> (especially with 
> inductive loads) through the PLC's outputs -even
> relay  outputs. I've had Siemens 
> micros "bounce back" after their contacts "stuck"
> from  too much current, but best 
> to include a separate glass fuse for each and every 
> output. Saves 
> programming time spent on re-assigning an output to
> a  spare...
>     Also hard to find a Siemens micro PLC with 
> 120VAC inputs. A-B still 
> makes those, tho. Most micros, except the very
> cheapest  models, have the 
> capability for expansion modules if you find you run
> out of I/O  for some reason.
>  
> -Phil LaBudde
> 
> 
> 


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