Electronics > Electronics

How to control AC powered device using MCU?


Hi all,

Short explanation:

I give 5v to [power control] --> AC Device ON
I give 0v to [power control] --> AC Device OFF

please advice  simplest & cheapest option for [power control]

P.S>I will not use relays

Long Explanation:

Basically I want to switch the AC (230V 50Hz) powered device on/off as per the MCU signals (Programmed logic ::))

for signalling I have 5v from normal I/O pins

I have considered Mechanical relays but I don't think they could run on the low current from the I/O pins .. further more I do not want to add a motor driver to control the relay as it will make the design  more complicated and much of the power will go for keeping the relays engaged!

So,I am looking for an electronic device/circuit for the purpose such as a MOSFET or something called as TRIAC

But, I am pretty dumb at electronics

can someone recommend a decet way to control the AC power to device using just the 5 v

Microchip has a few App Notes on controlling AC from micro-controllers.

Then the makers of the AC switching devices will have data sheets and App Notes on their usage.


--- Quote from: allahjane on December 09, 2012, 09:07:36 AM ---So,I am looking for an electronic device/circuit for the purpose such as a MOSFET or something called as TRIAC

--- End quote ---
If you absolutely hate the thought of a relay with a small signal transistor driving it (which is the cheap and easy way), either go for an SSR (Solid State Relay) or make on yourself from a zero-cross switching opto coupler (like the MOC3040, or better the IL410) and a TRIAC.

Relay + BS 170 (or other small-signal transistor) seems the most robust, and will give you a galvanically isolated solution. This is important from a safety point of view!
http://www.digikey.com/product-detail/en/G5LE-1A%20DC5/Z3115-ND/369007 ($1.49 qty 1)

I've also used these SSRs myself and they work fine -- but you need a double-insulated box, as it's not galvanically isolated:
http://www.digikey.com/product-detail/en/S216S02F/425-2414-ND/720364 ($6.26 qty 1)


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