I'm working on an electronic product based on a microcontroller that must be able to control a series of actuators: 230V AC motors ON/OFF, 24V DC motors ON/OFF, 80V/20A heating element ON/OFF. The obvious way would be to use relays (in combination with optocouplers perhaps), but they have the downside of having a short life cycle. My product must have a +10 years lifetime, so what the best way to replace the relays in this design and still have galvanic isolation?
Answer
You don't need an optocoupler to drive a relay; the relay has insulation already.
But your switching requirements are indeed high for a typical relay; we're talking about 2.6 million operations over the 10 year lifetime. There are relays which can handle this, but they're high endurance industrial devices, which will cost a lot more than an electronic solution.
There are a number of solid-state solutions.
For the 230V AC motors you can use a solid state relay (SSR), either as a module, or built with discrete components around an opto-triac + power triac.
The DC motors can be switched with MOSFETs, again controlled by an optocoupler, or with a DC SSR.
For the heating I presume the power is also AC. Then you can use the SSR, like for the 230V motors. If it's DC I would use MOSFETs.
(the linked to datasheets are just examples to get you started)
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