How to install an electric drive on the window for automatic ventilation of the greenhouse

Recommendation points

• Sash insert
• Hinge device
• Which drive is right
• Transmission parts
• Automation devices
• Scheme and principle of operation

During the growing season, plants need periodic renewal of the greenhouse atmosphere, especially during daylight hours. It is unlikely that you will want to get up at 4 in the morning every day to open the window in time. Therefore, we share one of the best automation tools for ventilating greenhouses..

Sash insert

Greenhouses really have a lot of device variations: from lightweight structures on a steel tube frame to completely capital structures. However, most of them have a honeycomb device, so the insert of an openable sash in one of the rectangular cells is seen in the most obvious way..

Even if the greenhouse is covered with film materials that are changed from year to year, the sash must be covered with durable sheet materials: polycarbonate, transparent PVC slate, glass and other light-transmitting materials. The window frame should be knocked down from light wooden slats, here are some tips for its construction:

• choose a cell as high as possible, close to the skate;
• turn over the opening under the sash with a metal corner for a tight vestibule;
• place the hinges outside in the upper part of the sash;
• down and to the sides, the sash cover material should be released 150 mm;
• the upper edge of the window is 100–120 mm covered with a strip of chamber rubber or silicone tape. The same amount is started under the greenhouse cover above the sash or under the ridge;
• do not make the sash too massive. In large greenhouses, it is better to make several small vents instead of one huge one..

1 – greenhouse frame; 2 – metal corner; 3 – wooden lath frame; 4 – translucent material (polycarbonate, glass); 5 – rubber (cuffs)

Hinge device

The opening mechanism is based on the principle of linear pushers for swing gates. A piece of angled steel with a shelf of 20 mm, 15 cm long, is attached to the end of the window through a conventional canopy for wooden window frames. With this fastening, the corner should fold in the direction of opening, and an M10 nut is welded at its lower end..

The second part of the mechanism is made of a steel strip 4×40 mm bent in the shape of the letter P. The distance between the shelves should be a couple of millimeters more than the thickness of the engine used, and the total length of the bracket should be 200 mm longer than the length of the motor shaft. Two 10 mm holes are made at the edges of the strip, the whole structure is suspended on two corner pieces, which, on the one hand, are rigidly fixed to the greenhouse frame, and on the other, have an 80–100 mm outlet under the sash. The U-shaped engine mandrel is inserted between the two shelves of these corners, the hinge is fastened with M10 bolts.

The engine itself inside the frame is also easy to fix. Make two 4 mm holes in the centers of the side shelves, cut the threads and tighten the motor housing with the screws. You may also need a hole in the center shelf of the mandrel to easily route the power cables to the rear of the motor.

Which drive is right

One of the most affordable engine options for driving a window can be called a DC motor (with a gearbox) from an electric screwdriver. The drive produces a solid force and has an optimal speed for mechanisms of this kind, the motor is also quite tolerant of temporary overloads.

The engine body is cylindrical, depending on the model of the screwdriver, its diameter can vary from 40 to 65 mm. The electrical connection is made at the rear. If two contact plates protrude from the body, you need to connect a piece of wire up to 2 meters long to them by soldering or using automotive plug-in terminal blocks. If two conductors simply come out of the plastic plug in the rear end – extend the power wires using a screw block.

In various versions, the motor can have one housing with a gearbox, or these elements are fastened by means of a plastic housing of the tool itself. It is recommended to purchase the cheapest single-speed screwdriver for the window and saw off the handle with a battery with a hacksaw. So you get a motor with a gearbox assembly, a power source and a chuck in which it is convenient to clamp the transmission shaft..

Transmission parts

Conversion of rotary motion into translational motion is performed by a worm gear, which includes a nut welded to a piece of an angle on the sash, and a 100 cm stud with a metric thread, which is rigidly connected to the motor shaft.

The main difficulty will be finding a suitable reducer for coaxial transmission between the shaft and the stud. If nothing fits the standard options, let’s be smart and take the time to filigree work. Clamp the pin in a vise and drill a longitudinal hole in its end, the diameter of which corresponds to the thickness of the shaft. The hole depth is 12-14 mm, try to make it as coaxial as possible with the hairpin, periodically wet the drill with machine oil.

At a distance of 20 mm from the same edge, file two grooves on both sides with a file. In their center, make another through hole with a 3.3 mm drill, then go through the tap number 1 and cut the metric thread by 4 mm. If the thickness of the shaft is 2 mm or more, make a couple of notches on it with a triangular needle file so that the distance from the edge corresponds to the position of the holes in the hairpin. Use screw pins from door handles or regular bolts to tighten the shaft tightly.

Automation devices

Start by making it possible to open and close the window at the touch of a button. The minimum required for this is two limit switches with normally closed contacts. One of them is attached to the corner on the sash. Here you can use the usual button, which will be triggered by pressing the end of the pin in the closed position of the sash. The second limit switch should preferably be lever-operated; it should be tied to the sash body with a thin copper wire.

The second stage is timer operation. Use electronic devices with daily or weekly programming, so you don’t have to “cock” the timer every day, and the window can work for months without human intervention.

Of course, it is also allowed to use light sensors in order to tie the ventilation mode to the daily biorhythm of plants. However, there is a pitfall here: the temperature at dusk and dawn is not always high enough, so the system must be supplemented with an electronic thermometer that will not allow the sash to open if it is too cold outside..

Imagine a similar situation in the middle of the day, which is typical of early spring. It would be nice to close the sash temporarily when the temperature drops; for this, the system must be properly configured for feedback between all sensors and control devices. This is impossible without a normal relay group (if the circuit is on relay type devices), so remember: both the timer, and the thermometer, and the photo relay must have at least one changeover (NO / NC) contact. For reversing motor control, you also need an intermediate relay with two changeover contacts..

Scheme and principle of operation

Power will require any 12 or 18 volt DC source depending on the motor selected. It is convenient, for example, to solder to the contacts of the battery and set it to “eternal” charging under a standard pulse source.

Power is supplied from the source to the output terminals of the contactor in a reversible manner. It is important to note that the power supply is interrupted here by the normally closed contacts of the limit switches S1 and S2. The logic of operation is as follows: if it is necessary to open the leaf, power is supplied to the contactor, which turns on the motor until its power is interrupted by the switched off limit switch.

Option 1

Such a scheme of operation is the simplest in its logical design: when the contactor is on, the leaf is open, and when it is turned off, it closes. If you are confused by the high intrinsic consumption of the circuit, use two separate contactors, but in this case, the right side of the circuit (control) will have to be somewhat complicated. In this case, the contacts of the limit switches are transferred from the load circuit to the control circuit of the coils of the intermediate relays.

Now we will consider two particular versions of the control scheme. In the first, normally open contacts on the timer and thermometer are enough, they are simply connected in series in the expectation that when the circuit is broken, the intermediate relay will turn off and close the leaf. For a simpler circuit design, you have to sacrifice high self-consumption and relay service life.

Option 2

In the second case, we have a similar series connection: the timer has a signal at the toggle relay input only at a certain temperature. Otherwise, the normally closed contact of the thermometer will give a signal to lower the leaf, which will be interrupted by the limit switch, as a result of which the relay will turn off and cannot turn on again until the leaf moves in the opposite direction..