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Relay output options

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justin_t

New Member
Hi

Im designing a circuit in which a micro-controller is used to switch an output.
Im looking at my different options.

In my circuit im using 240VAC mains through a PCB mounted transformer, rectifier, smoothing capacitors and 5V regulator to provide 5VDC for my control circuit.

I need the circuit to drive 4 outputs that can be used to switch items such as relays and perhaps small sounders, nothing with large power consumptions.
As Im using 240 VAC supply to the unit i dont want to have to use a dedicated 24 VDC supply to drive the coils of any outside equipment so the outputs from my circuit should be able to switch 240VAC.

Ive looked at a few PCB mounted relays that are capable of switching 240VAC but was wondering what my options are with things like Triacs and MOSFETS even solid state relays.

What is the difference in a Triac and an SSR?

Any help appreciated.

Justin
 

MikeMl

Well-Known Member
Most Helpful Member
The advantage of relays is that the 240V line side can be kept totally isolated from the 5V supply and the low voltage outputs from the uC. Solid-state relays use internal opto-isolation accomplish the same thing. If you would like to use SCRs or TriACs, then include opto-isolators between the uP and the gate circuits of those devices. You are, in effect, building your own SSRs.
 
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