Automatic egg incubator (2)

The automatic incubator for poultry eggs introduced in this example has the functions of automatic constant temperature (temperature adjustment range is 35-40℃, ±0.5℃) control and automatic timed egg turning (automatically turning the eggs every 1.5 hours), which can improve the hatching rate of poultry eggs and can be used in small hatcheries or ordinary households.

How the Circuit Works

The automatic egg incubator circuit consists of a power supply circuit, a temperature detection control circuit and a timed egg-turning circuit, as shown in the figure.

The power supply circuit consists of a power switch S, a power indicator light HLl, a power transformer T, a rectifier bridge UR, a filter capacitor C7-C10 and a three-terminal voltage regulator integrated circuit IC2.

The temperature detection control circuit is composed of resistors Rl-R6, capacitors Cl-C4, transistors Vl, V2, thermistor RT, thyristor VTl, heating indicator light HL2 and heater EH.

The timing egg-turning circuit is composed of a time-base integrated circuit ICl, resistors R7-R9, capacitors C5, C6, thyristor VT2, motor M and egg-turning indicator light HL3.

After S is turned on, HL1 lights up, and the 220V AC voltage is stepped down by T, rectified by UR, filtered by C7 and C8, and stabilized by IC2 to generate a 9V (Vcc) DC voltage. In addition to supplying ICl, this voltage is also used as the working power supply of V1 and V2 after being limited by R2 and filtered by C4.

When the power is just turned on, the temperature in the incubator is lower than the set temperature value, and the resistance of thermistor RT is large, so the voltage across C3 is higher than 0.7V, Vl and V2 are saturated and turned on, so that VTl is triggered and turned on, and the electric heater EH is powered on and starts heating, and HL2 lights up at the same time. As the temperature in the box gradually rises, the resistance of RT also slowly decreases. When the temperature in the box reaches the set temperature, Vl and V2 are cut off, so that VTl is turned off and EH stops heating. Then the temperature in the box begins to gradually decrease again. When the temperature is slightly lower than the set temperature, Vl and V2 are turned on again, VTl connects the working power of EH, and starts heating again. This cycle repeats itself, so that the temperature in the box is kept at the set constant temperature.

After ICl is powered on, since the voltage across C5 cannot change suddenly at the moment of power on, the voltages of pins 2 and 6 of ICl are lower than Vcc/3, pin 3 outputs a high level, Vn is in the off state, motor M does not rotate, and HL3 does not light up. At the same time, the +9V voltage charges C5 through R8 and R9, causing the voltages of pins 2 and 6 of ICl to rise continuously. When the voltage across C5 is charged to more than 2Vcc/3, the circuit inside ICl flips, C5 discharges through the circuit inside R9 and pin 7, and pin 3 changes from a high level to a low level, causing VT2 to turn on, M to turn on, and drive the egg frames of each layer through the deceleration mechanism and direction change mechanism in the incubator, causing one end to rise slowly and synchronously, and the other end to fall slowly and synchronously (with the movable axis in the middle), and the eggs in the egg frame flip gently. When one end of the egg frame rises to a certain angle, the voltage across C5 has dropped to Vcc/3, and pin 3 of IC1 changes from a low level to a high level, VT2 is cut off, and M stops, completing an egg flip. Then C5 starts to charge again, and when the voltage across it reaches 2Vcc/3, VT2 is turned on again, M is powered on, and the second egg turning begins. This process is repeated endlessly, thus achieving the purpose of timing egg turning.

Adjust the resistance of RP to set the desired incubation temperature.
Change the resistance of R8 to adjust the time for turning the eggs.
Change the resistance of R9 to change the working time of the motor M. After the eggs are incubated, a basin of warm water should be placed in the incubator to adjust the temperature inside the box. A small amount of warm water should be added to the basin every day.

Component selection
R1, R3-Rg are all 1/4W carbon film resistors or metal film resistors; R2 is 1/2W metal film resistor.
RP is a multi-turn potentiometer.
RT is a negative temperature coefficient thermistor with a resistance of 2-4kΩ at room temperature.
C1, C3-C5 and C10 are all electrolytic capacitors with a withstand voltage of 16V; C2, C6, C7 and C9 are all monolithic capacitors; C8 is an aluminum electrolytic capacitor with a withstand voltage of 25V.
Vl is a 59013 or C8050, 3DG9013 silicon NPN transistor; V2 is a 59012 or C8550, 3CG9012 PNP transistor.
VTl is a 6A, 400V bidirectional thyristor; VT2 is a 3A, 400V bidirectional thyristor.
UR is a 1-2A:5OV rectifier bridge stack.
IC1 uses NE555 or μA555, CC7555 type time base integrated circuit; IC2 uses LM7809 type three-terminal integrated voltage regulator.
HL1-HL3 uses 3 colors of 220V indicator lights.
EH uses two 100W electric blanket heating wires in parallel.
T uses a 3-5W, secondary voltage of 12V or double 6V power transformer.
M can use the reduction micro motor on the outdoor TV antenna.