Triac or relay to switch AC power?

Use triac then. The current will be no more than an LED.

Get a wind-up timer and be done with it. Fits right into the box in the wall and does everything you asked for. mike

Consider a solid state relay. Easy hookup. I use a 25 amp SSR and PIC-based timer to cycle a 1500 watt space heater that used to be inop. because its thermostat had died. Ten years old last fall and still running fine.

The lowest power usage I can think of is by using a bi-stable relay. It only uses a bit of current when switching on or when switching off.

Joop

The simplest way to achieve success without knowing much about electronics is to use an AC relay actuated by a your controller through a TRIAC. The sizing of the relay driving an incandescent load has to be adjusted downward from the maximum current rating of the relay to something like 30-40% because of the cold filament surge and possible filament failure scenarios. So if your bulb is say 300W @ 240VAC, then I=W/V=300/240=1.25A -use a relay with contacts rated at 5A @240VAC and

View in a fixed-width font such as Courier.

Maybe the simplest in your case would be to use a DPDT AC relay configured as self-latching, and then use timer to pulse two logic level mini-relays ( one with normally close,nc, the other with normally open ,no, contacts) with AC rated contacts to initiate ON/OFF operation. The quiescent overhead from the controller is now zero. View in a fixed-width font such as Courier.

. . DPDT AC PWR RELAY . +--------------+ . | / | . LINE -----------|--+-----o o---|----------------->

. | | | TO LAMP . | K|| | . | K|| | +---->

. | K|| | | . | K|| | | . | K|| | | . | | | | . | +--------+ | | . | | | | | . | o | | | . | / | | | . | o | | | . | | | | | . +--------------+ | . | | | . | | | . o o | . nc |

Relay DPDT Self-Latching connection I want to use VCC=5V to drive a 120AC line. How would you connect the DPDT relay as self-latching?

VCC----+ | | | | | | | | +-----------------------------------------+ | | NC COM NO NC COM NO | | K|| | | K|| | | K|| | | K|| | | K|| | | K|| | | K|| | | | | +-----------------------------------------+ | | Ground----+

A relay that "self-latches" is not a latching relay. Latching relays maintain their last state without power applied to the coils. Because you are concerned about power consumption in the timer, you either power the relay off the AC line or use a true latching relay. It will be cheaper for you to use surplus standard 5VDC coil relays that you

From Fred's point of view, I think VCC should be replaced by the LINE with a connection like this:

This way, the consumption is not from the controller/timer "board" because the board drives the two small relays with pulses, but there is still consumption for this "AC" relay from the LINE while the load is powered. To take the overall consumption at a minimum, a latching relay should be used? Or how much current, voltage or power this AC relay takes when there is current in its coil?