driving a contactor from a digital signal

[normad]

hey guys what do you think is the best way to drive a high current contactor from a digital signal(from a pic probably) its a 24 volt contactor coil but im not sure how much current it will take. im thinking of using a darlington pair. is there a better alternative?
thanks

 

[Reloadron]

its a 24 volt contactor coil but im not sure how much current it will take.

That is a problem, as to know the best way to drive it you really need to know the contactor coil current. Got a model number or data sheet> Can you energize the coil and measure the current?

Ron

 

[Nigel Goodwin]

A contactor is just a big relay - as suggested you need to know it's requirements.

Contactors often need to be fed by a relay, with a transistor feeding that relay - because of their fairly hefty requirements.

 

[normad]

im really not sure and i dont have the contactor with me ryt now. im just trying to get an insight on my driving options cause i will be designing the control circuit looking at a few datasheets im guessing the current would be from 300 to 700mA

 

[Nigel Goodwin]

im really not sure and i dont have the contactor with me ryt now. im just trying to get an insight on my driving options cause i will be designing the control circuit looking at a few datasheets im guessing the current would be from 300 to 700mA

What is the unit?, and how big is it - contactors are normally pretty large items.

 

[normad]

once again i dont know what the unit is or how big it is.. but i can tell you the application.. its to drive outputs from a multitap transformer.. input to the transformer is 230V and there are seven outputs ranging between 195V to 305V. the contactors are used to keep only one of these outputs driving at a given time

 

[ronv]

You should be safe with something like the IRL540. Don't forget the diode across the coil.
https://www.electro-tech-online.com/custompdfs/2010/11/91300.pdf

 

[normad]

hm.. that seems to be within the range thanks a lot..

 

[MikeMl]

To prevent Resetting the PIC due to GND bounce when the inductive coil in the contactor switches off, I would not tie the 24V power supply to the PIC's 5V supply, and use an opto-isolator between the PIC Port and the Gate of the NFET.

There are hundreds of posts on these forums about "why is my PIC resetting when I switch an inductive load?"

 

[normad]

oh.. wouldnt using two different regulators be enough to solve the problem? i need to do a bit of reading on the subject thanks a lot for the heads up