How to open the greenhouse door in the morning?

Question

Do it yourself

Given: greenhouse. Task: in the morning the greenhouse door should open on its own. In the evening I will close it myself, and the next morning it should open again.
There you can supply power, for example, 12V. You can make control automation on a microcontroller (MK). But most importantly, how do you open it? As options for seeding (in all options, door retention is used, and after it is lowered, the door opens, for example, with a tensioned spring):
1. Electromagnet as on access doors. The issue price is just over a thousand rubles. They can be controlled with MK.
2. Electromagnetic lock, latch type. It closes itself, opens by powering the solenoid. The price is a little cheaper. On the plus side, battery life is sufficient. Of the minuses - when there is no power or the automation fails, you will have to remove the polycarbonate in order to get inside.
3. A thin rope stretched from the inside through the hole in the door to the outside, and outside is knotted. Easy to untie in case of automation failure. But how to let it go or cut it from the inside? For example, burn it with nichrome wire?
What other options, I want cheap, affordable. Or I'll go for an electromagnet.
PS Yes, manufactured industrial oil cylinders for greenhouses, electric cylinders, etc., are not suitable, because they are for vents. But there are plans.

Answer 1

Old soviet alarm clock + fishing line

Answer 2

Once I made an automation drive from a winder for the rear wiper of a Zhiguli-Nine. You give him + 12V to the control contact for a short time - he makes a turn of 120 degrees, and returns back.
In your case, it will push the door and come back. The door will remain open - it will stick to the magnet, or else how it will be fixed.
The motor will fit any hatchback. Price - as agreed upon disassembly. Isn't a new one needed?
Food - 12B or the accumulator from UPS'a.

Answer 3

Turn on the electromagnet in parallel with the photoresistor (add transistor-amplifiers to taste).
While it is dark, the resistor has a large resistance and all the current goes to the magnet. At dawn, the resistor will absorb light, lose resistance, and current will flow through it. At some point, the current on the magnet will not be enough to hold the door and it will open.
Controllers are not needed for such a task, and there are a lot of troubles with them, then give them 5 volts, then tightness.

Answer 4

the mechanism for automatically opening the windows on the door can be installed, sold here - https://metallnsk.ru/teplicy-v-novosibirske.html
2000 rubles price, opens / closes depending on the temperature.