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Is there a DC controlled AC switch available for sale? Answered

Hello everybody! I was wondering if there is such thing as a DC controlled AC switch. If that doesnt make sense, i guess im trying to say a switch of some sort that controls an AC current using a DC current. I am trying to control the switch with an arduino output and power the 120V light bulbs with it. The switch should be normally closed and stay on for the duration that the Arduino is supplying supplying the DC current. I read a bit about DC control relays, but not sure about those. Are tehy essentially the same thing, and if yes, should i go regular or solid state?



Best Answer 5 years ago

What you're looking for is exactly that; a relay.

just search arduino relay shield
...you'll find lots, like

20 bucks

they provide common, normally open, and normally closed circuits for each channel; the linked one with 4 channels and each can handle 360 VA (essentially watts).

It's opto-isolated so that it won't fry your arduino if something goes wrong.

Wow so on the right track i guess. The Arduino Relay Shield you showed me, does that already have the relays built into them? And if yes, can i run the 120v straight through those phoenix terminals?

The little boxes on there are each a separate relay, and the arduino controls a signal pin in the shield.

Bring the signal on (high) and the opto isolator turns on, which turns the relay on. You feed whatever voltage up to the max allowable to the relay pin header and it can be switched on or off.


5 years ago

It is called a SSR ( Solid State Relay )

The SSR turns on when a 5V and 3 to 10 ma DC current activates an
inside optical isolator.
Which activates a 400 Volt 20 AMP AC TRIAC  ( Power Thyristor ) switch.
That Semiconductor controls a light bulb, a TV or an AC Motor.

All this from a little 5 Volt DC microprocessor output pin..

Some SSRs actually sync with the zero AC line crossing.
This means the switch does not make static electrical noise on the main line
Because turn on and turn off occure at zero Voltage AC..
You need to understand when the uP turns the 5V signal ON the SSR
may be 16 ms before the zero crossing can begin to turn the .TRAC  ON.
As always when the uP turns the output pin to 0 Volts it may be  16 m\
before the AC zero crossing can begin to turn the .TRAC  off...



5 years ago

There are lots of them in use everywhere. One that you will recognize right away is the fan circut in your furnace. The furnace thermostat runs on DC. Depending on how fancy the unit is and how old, many of the older units used a DC control circuit that activated a relay to turn on the AC fan when the heat reached the proper level.

Some large classrooms and auditoriums use a relay to turn on all the lights. A relay needs to be DC in order to operate otherwise it will just vibrate the switch back and forth when it is energized. A relay on AC current is a buzzer.