The same 12-volt voltage is applied via its relay time delayed up to 15 seconds to measure the subunit responsible for the clarity and accuracy of measuring soil moisture. And if the latter is below the required level established individually for each plant, the output of the circuit appears a high level signal which is applied to the input of trigger control subunit. Actuating, the solenoid valve opens for a time determined by another time relay, an excerpt of which is set depending on the application rate, the vegetation size of the vessel and other factors.
After a predetermined time interval, the valve closes and water flow stops. The main timer automatically turns off the power supply, de-energizing both subsystems with the exception of the photocell, which is in the standby mode until the next morning. If the humidity of the soil the next time you turn normal, then watering will not occur. The system will reduce its guardianship over the plants only for the obligatory morning spraying — when triggered at dawn photocell.
Now about the features of the subsystem “sensor — water”.
The humidity sensor is a probe from strips of fiberglass, which removed a large part of the foil (top only left about 10 mm). Two piece graphite rod from a pencil (length 15-20 mm each) tightly coiled wire 10 mm and soldered to the foil stekloekspo-litovoi strips from opposite sides. On top of the leads soldered wires and the whole structure is sealed with compound.
The watering device used electrovalves, flexible, transparent pipe, plastic tees, as well as the electric motor of the windshield washer from the car VAZ-2109 (the capacity of the washer fluid tank is too small, so better take 25-liter plastic containers). In the motor to reduce noise and reduce the current consumption weakened pressure of the brushes.
Around the plant from the tube is minimized watering ring and on its inner side punctured a small hole. If planting seed, then the tube in the ring can not collapse and be routed between the rows. Nozzles of spraying taken from aerosol cans. These details arranged flowers on a U-shaped rod and connected in series.
Sometimes short stature or monolistenport plants spraying may affect the readings on the dipstick. In this case, it should be covered with a conical cap which should not come into contact with the soil. If the device is used over a large area, to a single measurement unit can be connected to multiple probes, located in different places.
About the operation of an electrical circuit. When the ambient light sensor VR1 increases its resistance, which leads to the closing of the transistor VT1. Transistors VT1— VT2 assembled Schmitt trigger to provide hysteresis for slow changing input signal and to ensure the smooth operation of relay K1.
When the gate voltage VT3, relay K1 closes the circuit of the load — subunit of the 12-volt supply. To ensure that he was included for a limited time (5-7 minutes), the VT4 transistor provides a discharge circuit R8C1. As soon as the capacitor C1 discharges to the threshold value, it opens the VT4, VT3, closing the shutter on a common wire, and relay K1 turns off. In this condition the scheme is until the next evening.
Fig. 1. The subsystem “sensor— water” for the automatic care of houseplants:
1 — water tank; 2 — elastic tubing (silicone or rubber tube); 3 — electrically-controlled pump; 4 — tee; 5 — water solenoid valve; 6 — ring irrigation; 7 — atomizer (spray from an aerosol can); 8— self-made humidity sensor; parts 3…5 — from washer of the car VAZ-2109; the number of parts 2,4…8 — in-situ; and — a bilateral foil glass fiber; b— electrode (graphite pencil, 2); — pin wire winding; g — output (wire type mgshv, 2); d — protective case (compound or cut vinyl tubing)
Fig. 2. Schematic and functional scheme of automatic control spraying and watering taking into account the individual characteristics of plants
In the afternoon the capacitor C1 discharges through resistors R6 and R8. So at the next light sensor relay will energize during the time interval specified by the values of R8 and C1.
The device is powered from the grid in the transformerless scheme to reduce energy consumption. In standby mode it consumes a current of about 30 milliamps.
Subunit 12-volt power outlet, the device also has a time limit similar to the photocell. But the time limits are different — 15 seconds, set by circuit parameters R14C7.
The scheme of measurements collected on the comparator threshold which is set by trimming the resistor R19. Under the handles adjust R17 and R19 are paper washer is a kind of scale divisions.
Engine “podstroechnye” R19 is set in the middle position. The probe is inserted into the soil with the desired moisture content. Knob R17 is selected when switching the relay circuit. The adjustments are done for each plant (each channel) separately.
The trigger on the chip DD1 provides clarity to the relay circuit. To limit the duration of its retention (and hence irrigation), enter the delimiter which is selected by the values of resistor R24 and capacitor C12. For easier debugging the hardware changes from one plant to another, these circuit elements made in the form of a removable module. It is useful to have at hand a number of modules that are configured for different time (from several seconds to several minutes).
Almost all the information about the details contained in the circuit diagram. You can only clarify that fixed resistors — type MINTS, and trimming — SP-3-19, and R17 and R19 can be replaced by fixed resistors after measuring different levels of soil moisture. Capacitors C1, C2, C4—C12 widely known types K50-35, Sz — K73-17 at 500 V. the Relays can use any, as long as their coil was designed for 12V, and the contacts work reliably when the switching current of 0.6 A.
Transformer ready-made or homemade, with two secondary windings, is able to give to the load at 12 V At a current of 1 A (stable for electronics) and 8 (normal, to power the solenoid valves and pump motor). The parameters are named, with some margin, with the expansion devices and connection valves the new rate of 0.4 A for each valve.