I just got a Univent automatic opener that opens and close a cold frame lid. I’ve wanted one for a long time. This will save me time running out and opening it on a warm fall day (so my veggies don’t cook) and then running back and closing it when it gets cold later in the day (so they don’t freeze). It is a temperature sensitive opener designed to open windows in greenhouses or lids on cold frames. It can be adjusted to start opening between 60-75°F. It fully opens at 86-90°F up to 18″ and fully closes at 55°F.
Here is a little info from ACF Greenhouses on them- “How do automatic vent openers work? Vent openers do not require electricity. The opener has a metal cylinder containing a mineral which expands when heated. This pushes a piston that opens the vent. As the temperature cools, the mineral shrinks and a spring closes the vent and resets the piston. The opening and closing of the vent is gradual allowing just the right amount of air flow for cooling.”