I need to switch multiple DC contactors on and off using Arduino.
I have not found any single component that can switch the contactor directly from the Arduino's output, due to voltage and current requirements/limits.
As such I am looking at a 4-step approach where each device switches the next:
arduino digital output pin (3.3v?) > optoisolator (12v) > solid state relay (12v) > contactor (100v)
I'll be running 4 of these from one Arduino so need to consider the cumulative current draw when active.
To my extreme beginner eye, it feels a little convoluted to have so many steps, am I missing something or is this perfectly valid?
Thank you, here's the info/links to the components I'm looking at.
Arduino: Teensy 4.0
Maximum Digital output 3.3v/4mA ?
Optoisolator:
3.3v input, presumably low current draw since it's using optoisolators? (I will likely try and find one of these with more info available)
can control a 12v output.
Using two types of solid state relay:
SSR-DD41F - I need to control three of these
*it's the DD41F version I'm looking at, the page may load a different variant.
*looks like the typical switching voltage of this relay is 1.4-4v, with typical current 6.5ma. If the Teensy 4.0 can deliver 4mA max on its output pins it seemed that this would be overstressing it? (PLEASE correct my understanding if wrong, it's shaky at best)
The contactors are TE
EV200AAANA
They have a max inrush current rating of 3.8A, it's been problematic to find a solid state DC relay that is rated for this current + safety margin while having a low enough switching requirement.
You could use just common (optoisolated) relay module for that. Most of them can switch 12V DC.
I don't know what you mean with "single component" though.
Thank you - that would be a board which has the optoisolators AND mechanical relays on it, correct? Something like this?
By single component I meant I couldn't find a solid state relay that was capable of switching the 100vDC load I need, without requiring a 'trigger' voltage/current that was more than the Arduino could supply natively.
This is like drinking from a fire hose for me though so my understanding is basic at best.
The duty cycle of the solenoid switch. That is the only device you have that generates heat when in active use. The coil generates heat that must be allowed to escape or it will build until something gets too hot. The contacts have resistance and get hot, so the heat needs to disparate somehow. Likely the terminals and connecting wire will act as heat sinks.
That leaves the coil heat. The specifications for the switch will give the duty cycle which is the ratio of time on making heat to time off to allow cooling. Too much time powered on will eventually cause failure of some sort.
I've searched through the datasheet for my contactor but I couldn't find anything related to duty. I saw some timing information on the open/close speed. (I linked it below)
It does have a coil economizer that (if I am tracking) greatly reduces the current required to keep it open once it's opened. Is it possible that feature would allow it to remain energized 'indefinitely', or is that impossible?
A common mosfet module with surface mount fets would do the job of driving the coil.
The relay seems to be a starter motor type, for very short duration use only.
A mechanical relay like that will almost certainly burn out with continuous use.
An inductor (relay coil) has no inrush current.
Leo..