Using a timer switch for power, how to wire two lights so that when one is on the other is off. In the dull and cold winter days I am trying to grow seedlings. The light is insufficient during the day and so is enhanced with grow lights, which should be off at night, but the nights are cold so I want pad heating on then.
You could use a smart plug like a Shelly Plug which will allow you to set up time with built-in tools to automatically turn on and off at dawn and dusk and be controllable with a smart phone. The advantage is that the Shelly is smart enough to automatically adjust to changing daylight hours, which a wall timer will not usually do.
It's hard to argue with the simplicity of a simple timer that @Tim suggests comments for your question.
There are timers which will allow you to control two different devices from the same power outlet. An example would be the NearPow Outlet Timer, which allows two different devices to have nine on/off settings per day and seven day programmable.
Good luck with the plants.
Power the heat pad through dusk to dawn sensor.
Most are for bulb sockets, which you can convert with a socket-to-plug adapter, but there's also plug-only switchers with photocells.
if ambient light isn't enough to trigger cleanly, get an extension cord from the timer's output and plug in both the grow light and a nightlight to it. Then tape the nightlight onto the front of the dusk to dawn so that when timer has power, the sensor doesn't, and vice-versa. I use these photocell-based consumer electronics "logic inverters" with LED nightlights in several places in my smart home setup to avoid modifying electronics.
To be clear:
- the wall powers the timer and dusk to dawn switcher
- the timer powers the heating pad (and optionally a nightlight to extend the light)
- the dusk to dawn powers the heating pad.