--- Carl Denk <cdenk@alltel.net> wrote:

I am not an engineer in training but I continuously
drive myself to learn more electronics. :)

> I'm not an electrical engineer  :( , the formal
> training in that area 
> was 1 semester in 1963, and haven't calculated any
> of that. There was 
> question in my mind if the relay would actually
> switch over quick 
> enough, that the latency of the power supply and PLC
> would cover the 
> time. Since I had the necessary hardware laying
> around, I tried it, and 
> it worked on the bread board. Went through 2
> versions of the PCB where 
> other things changed (AC voltage and frequency
> measurement to the PLC is 
> on the same board). It was just recently I stumbled
> on the issue, after 
> a year of operation, it has switched over OK many
> times with utility 
  
  As time pass by the age of the components start to
show like increased resistance and etc.

> power, and then with generator power it fails in the
> direction of the 
> spring moving the contacts every time. In the
> direction that the coil 
> moves the contacts, it's OK either power source.
> 
> By asking when does it actually switch over, I
> assume you are talking 
> the brief time from when the 120 volt is down to the
> contacts moving. 
> All I can say is the 120 volt wire to both  the
> relay coil and the 12 
> VDC power supply are the same length from the plug
> strip within say 6". 
> The power supply is a International Power model
> IHC12-34 with over 
> voltage protection.
> 

  http://www.allaboutcircuits.com/vol_1/chpt_16/3.html
Read this instead for the calculation. The difference
of the wire resistance is minimal at best. I believe
there is some where at the site above to calculate the
wire resistance. There are other resistance to
calculate.... The input of the PLC is one for example.




John


       
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