Do it yourself DIY a smart fish tank: schematic design and circuit analysis

The tropical fish tank water temperature automatic controller automatically heats the fish tank by heating gas by using a negative temperature coefficient thermistor as a sensing probe. The transient time of this circuit has been smaller, which is conducive to temperature control accuracy, and it is suitable for various large and small fish tanks. Circuit Working: After the diode VD2 to VD5 is rectified, the capacitor C2 is filtered, and the control portion of the circuit provides a voltage of about 12 V. 555 Time Circuit is connected to a single stable trigger, transient is 11s. The control temperature is 25oC, and RP + RT = 2r1, RT is the thermistor of the negative temperature coefficient by adjusting the potentiometer RP. When the temperature is less than 25oC, the RT resistance is increased, and the 2 pin of the 555 time base circuit is low, then the 3 pin is changed from the low level output to a high level output, the relay K is turned on, the contact is bonded, The heating tube begins to heat until the temperature returns to 25oC, the RT resistance is small, and the 2 pin of the 555 time base circuit is at a high level, and the 3 pin outputs low level, the relay K is absent, the contact is disconnected, and the heating is stopped. Selection of components: IC selection of NE555, μA555, SL555 isometric integrated circuit; VD1 is selected for IN4148 silicon switch diode; LED uses ordinary light emitting diodes; VD2 ~ VD5 is selected for IN4001 silicon rectifier diode; RT selection 470Ω MF51 Temperature coefficient thermistor; RP selection WSW organic solid microminal potentiometer; R1, R2 selected RXT-1 / 8W carbon film resistor; C1, C3 selected CD11-16V type electrolytic capacitor; C2 selected CT1 ceramic capacitor; K Use the working voltage 12V JZC-22F small medium power electromagnetic relay. Production and debugging method: Temperature sensing probe connects the thermistor RT to the plastic wire, and then seal the welding point with RT with Epoxy gum, so it is not afraid of water erosion. As long as the circuit is correct during the production, the circuit is easy to implement, and if the component performance is good, it is not necessary to debug after installation.

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