The teaching instruments belonging to the biochemical incubator are widely used in colleges and universities, medicine, biology, scientific research and other fields. Do you all know the circuit composition of a biochemical incubator? The control circuit of the biochemical incubator consists of a temperature sensor, a voltage comparator, and a control execution circuit.
The biochemical incubator can be modified with an old single door or double door refrigerator: using the refrigerator's own functions for cooling, heating devices (such as electric heating wires or iodine tungsten lamps above 150W) and exhaust fans (to make the temperature inside the refrigerator uniform) can be installed below the refrigerator.
The potentiometer RPl is used to set the upper limit of temperature, and RP2 is used to set the lower limit of temperature. The temperature sensor circuit adopts a new type of temperature sensor integrated circuit ICL.
The voltage comparator circuit consists of resistors Rl-R7, temperature setting potentiometer RPl, R-resistor, and voltage comparator integrated circuit IC2 (Nl, N2). The control execution circuit consists of transistors Vl, V2, relays Kl, K2, and diodes VDl, VD2, etc. Relay Kl controls the heating element through a heating intermediate relay (not shown in the circuit), while relay KZ controls the refrigeration system of the refrigerator through a cooling intermediate relay (not shown in the circuit).
The 5th and 2nd pins of IC2 are connected to the center plugs of RPl and RP2, respectively. The 6th and 3rd pins of IC2 are connected to the output terminal of ICI through resistor R3. When the voltage value of pin 2 minus the voltage value of pin 5 of IC2 is approximately equal to 0 · OlV, the corresponding temperature is 1 ℃.
When the temperature inside the biochemical incubator is within the set temperature range, the voltage at pin 2 of IC2 is higher than the voltage at pin 5, and the voltage at pins 3 and 6 is equal to the voltage at pin 2 (or lower than the voltage at pin 2 but higher than the voltage at pin 5). Both pins 1 and 7 output a low level, VI and V2 are turned off, relays Kl and K2 are not closed, and the cooling and heating circuits are not working.