29-09-2012, 05:00 PM
Kitchen Fan controller with LM35 and LM3914
Kitchen Fan controller.docx (Size: 633.14 KB / Downloads: 350)
This is a very simple temperature controller circuit diagram which can be used any where to control the temperature with fan. The temperature sensor LM35 is used to sense the temperature and the controlling device is LM3914
Above is the Circuit Schematic for Kitchen Fan Controller:- Exhaust fan is an important component in kitchens. Here is a simple circuit to control kitchen fans by monitoring the ambient temperature. It is built around the renowned precision integrated temperature sensor chip LM35 (IC1). Rest of the circuit is a non-traditional electromagnetic relay driver wired around the popular LED driver LM3914 (IC2). User can switch three presetted temperature levels using a jumper/slide switch (JP1), which determines the heat level to activate the relay and hence the electric exhaust fan wired through the relay contacts. It works off 12V DC power supply.
Only one adjustment is required in this kitchen exhaust fan controller circuit. After construction, set jumper point in its first position, ie base terminal of T1 is connected to pin 13 of IC2 and adjust the preset P1 carefully so that relay RL1 is energised when ambient temperature level reaches near 29oC. However this is not very critical as you can select any threshold level by connecting the jumper points to other unused output pins of IC2 (here only 3 outputs are used).
In this project a Exhaust fan is being controlled which is an important component in kitchens. The project is a simple temperaature controller to control kitchen fans by monitoring the ambient temperature of kitchen regularly and give the commands to fan accordingly. The sensor or transducer used in this temperature controller is precision integrated temperature sensor chip LM35 (IC1). The decision to turn ON or OFF is done with the help of LM3914 the popular LED driver LM3914 (IC2).
The prset temperature input to the temperature controller is feeded through the switches.User can switch three presetted temperature levels using a jumper/slide switch (JP1), which determines the heat level to activate the relay and hence the electric exhaust fan wired through the relay contacts. It works off 12V DC power supply.
Only one adjustment is required in this kitchen exhaust fan controller circuit. After construction, set jumper point in its first position, ie base terminal of T1 is connected to pin 13 of IC2 and adjust the preset P1 carefully so that relay RL1 is energised when ambient temperature level reaches near 29oC. However this is not very critical as you can select any threshold level by connecting the jumper points to other unused output pins of IC2 (here only 3 outputs are used).
Description
The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°C over a full -55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35's low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate over a -55° to +150°C temperature range, while the LM35C is rated for a -40° to +110°C range (-10° with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.