I am trying to control my boat lift with vex (eventually via computer). All I need to do is control the power to the lift (50 amp, 240 volt) to control the entire system. I am having a hard time finding anything that is rated to 50 amps.
I am thought of using transistors (specifically MOSFETS) and relays. I am having no joy with finding any 50 amp rated MOSFETS and relays.
Anyone have any other ideas or ways to do this?
Thanks
hmm…id continue your search for a transistor, i know it ca be a pain to find a high rated one…try jameco…robot shop (actually you might find a good relay there)…hvwtech
WHATEVER YOU DO, DO NOT USE AN UNDER RATED TRANSISTOR, THE HEAT CAN BURN VERY EASILY
50 Amps! You must be trying to lift the QE2!
Just to be clear, this is single phase AC?
How is it controlled now - it may be easier to interface to the existing control system than to create something from scratch.
You might be able to use a solid-state relay such as this one from Jameco. The specs aren’t clear enough to indicate if you could directly drive it from Vex or not - you might need a transistor or 7406 between the Vex and the relay to provide enough voltage/current to trigger the relay.
On a completely different note: Are you sure you want to use a Vex controller to run something this large? I’m sure the folks at IFI would warn you that the controller is not intended for use in critical applications where somebody’s life or limbs may be at risk. And I don’t expect the connectors are rated for use in a marine environment - you may have long-term reliability issues due to corrosion.
Hope this helped,
you will definitely need a bigass 50A solenoid, or solid state. not sure if there ARE 50A solid states… a solenoid is easier. add a optocoupler between vex and relay driver if you can. if you need to reverse direction, add a DPDT relay (50A).
please dont swear^ just warning you
Relays like that are called “contactors”
http://www.aero-inc.com/contactorfurnas.jpg
although you’d probably need yet another low current relay to make it work from something like a vex controller. And I second the suggestion to make sure this is a wise thing to do…
No need to worry, I am just doing this for fun. Nobody is near the boat lift when operated.
All that operates it right now, is a two way switch.
Sounds like it would be easier and cheaper to just use a servo to flip the switch.