DC source as an AC input for cheap?

I plan to take a +5v DC source as an input but my AB 1760 only has AC inputs. How can I make this happen. I want to use this as an interlock so that when there is no DC voltage, the permissive will be made and the output can be energized.

Use a relay with a 5VDC coil, and switch the AC to the PLC through the normally open contacts

AC------------------------>

        +-----+            TO PLC

AC------|-] [-|----------->

        |     |

      +-|-( )-|-+

      | +-----+ |

      |  RELAY  |

     +5V        0V

beerchug

-Eric

One more thing...

Don't forget the series vs. parallel lesson you learned in THIS THREAD!...

It won't be so funny this time... 120VAC in the wrong place WILL let the smoke out of the your little PLC pretty darn quick!...

beerchug

-Eric

I would think in this case that an error would let the smoke out of the relay not the plc..

I dont think applying 5vdc to a 120vac input would do much damage.

That's what you'd think, but you don't know what best49erfan's capable of!... utoh

Only kidding!...

beerchug

-Eric

u r right...he is a 49er's fan after all!

There ain't no such things as Aliens! (?)

I plan to take a +5v DC source as an input but my AB 1760 only has AC inputs. How can I make this happen. I want to use this as an interlock so that when there is no DC voltage, the permissive will be made and the output can be energized."

Just as a point of interest...
Your description indicates that you want to make a decision based on a "proven negative".

As in...

"I can't see any Aliens (DC), so there must not be any Aliens (DC)."

And then, through "illogical extention"...

"Since I can't see any Aliens (DC), there ain't any Aliens (DC), and therefore... it is OK for us to proceed with our plans of universal occupation... because we have confirmed that there is nothing in the way!"

Is it the case that "there are no Aliens (DC)" because in fact, "there are no Aliens (DC)"?

Or is it the case that "there are no Aliens (DC)" simply because you can't see any Aliens (DC)?

There could be any number of reasons that Aliens are not "seen".

• ineffective detectors
• they are hiding
• we are looking in the right place at the wrong time
• we are looking in the wrong place at the right time ?

Just stirring the pot a bit...

Terry is right!

If you were to blow a fuse on the AC supply feeding the relay you
could get a false off condition.
Hope this is not for a guard or other safety interlock

                      +-----+            

From Pico L1 AC>------|-] [-|----------->To Pico I3

                      |     |

                    +-|-( )-|-+

                    | +-----+ |

                    |  RELAY  |

                   +5V        0V

+5V from hard drive supply. When the PC is off, then you will have an input saying that the power to the hard drive is off. So, this is not a safety or anything like that. just a permissive so I cannot remove the HDD while there is power on it.

Also in response to the , not me! I am good at electrical stuff. Everyone makes mistakes and if I want to short out LEDs to burn them out, the I will!

rsdoran said:

u r right...he is a 49er's fan after all!

Click to expand...

I missed this part............. moon2 bonkhead