Shanghai Haozhuang Instrument Co., Ltd. has developed the LNB brand biochemical incubator, which is energy-saving and environmentally friendly, leading the country. The biochemical incubator has a two-way temperature regulation system of refrigeration and heating, and the temperature can be controlled. It is a scientific research institution, college, production unit or department laboratory in the industries of biology, genetic engineering, medicine, health and epidemic prevention, environmental protection, agriculture, forestry and animal husbandry The important test equipment is widely used in low temperature constant temperature test, culture test, environmental test, etc. The controller circuit of the biochemical incubator is composed of a temperature sensor, a voltage comparator and a control execution circuit.
Circuit principle: The circuit uses a new temperature sensor integrated circuit ICl. The voltage comparator circuit is composed of resistors Rl-R7, temperature setting potentiometer RPl, R Tuo and voltage comparator integrated circuit IC2 (Nl, N2). The control execution circuit is composed of transistors Vl, V2, relays Kl, K2 and diodes VDl, VD2, etc. The biochemical incubator can be modified from the old single-door or double-door refrigerator: use the function of the refrigerator itself to cool, install a heating device (such as an electric heating wire or an iodine tungsten lamp above 150W) and an exhaust fan (which can make the temperature inside the box Evenly). Potentiometer RPl is used to set the upper limit of temperature, RP2 is used to set the lower limit of temperature. The relay K1 controls the heating device through the heating intermediate relay (this drawing in the circuit), and the relay KZ controls the refrigeration system of the refrigerator through the cooling intermediate relay (not shown in the circuit). Pin 5 and pin 2 of IC2 are connected to the center plugs of RP1 and RP2 respectively. Pin 6 and pin 3 of IC2 are connected to the output of ICI through resistor R3. When the voltage value at pin 2 of IC2 minus the voltage value at pin 5 is approximately equal to 0 · OlV, the corresponding temperature is 1 ° C. When the temperature in the biochemical incubator is within the set temperature range, the voltage of pin 2 of IC2 is higher than the voltage of pin 5, and the voltage of pins 3 and 6 is equal to the voltage of pin 2 (or lower than the voltage of pin 2 and higher than pin 5) Voltage), pins 1 and 7 both output low level, VI and V2 are cut off, relays Kl and K2 are not attracted, and the cooling and heating circuits are not working. When the temperature in the box exceeds the upper limit of the set temperature, the voltages of pins 3 and 6 of IC2 will be higher than the voltages of pins 2 and 5 and pin 1 of IC2 changes from low level to high level, making V2 conductive. Relay K2 pulls in and its normally open contact is connected, the refrigeration system works. When the temperature in the box is lower than the lower limit of the set temperature, the voltages of pins 3 and 6 of IC2 are lower than the voltages of pins 2 and 5 and pin 7 of IC2 changes from low level to high level, and V1 is turned on. The relay Kl pulls in, its normally open contact is connected, and the heating circuit works. Components selection Rl-R5 all use 1 / 4W metal film resistors, the accuracy should be ± 1%; R6-R9 can choose 1 / 4W carbon film resistors. RPl and RP2 use wire wound potentiometers with higher precision. C selects monolithic capacitors. Both VDl and VD2 use 1N4148 silicon switch diodes. Vl and V2 use S9013 or C8050 silicon NPN transistors. ICl selects LM35DZ or LM36, TMP36 type temperature sensor integrated circuit; IC2 selects LM393 operational amplifier integrated circuit. Both Kl and K2 use l2V DC relay.
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