Wiring circuit

In most WCs with an extractor the fan is connected to the lighting circuit and is switched on and off either in sympathy with the light or with a short delay. Since toilets are sometimes used for washing the hands or just for a quick look in the mirror, it is not always necessary to change the air in the smallest room in the house. The following circuit automatically determines whether there really is any need to run the fan and reacts appropriately. No odour sensor is needed: we just employ a small contact that detects when and for how long the toilet seat lid is lifted.

 On-Demand WC Fan Using 555 circuit diagram

If the seat lid is left up for at least some presettable minimum time t1, the fan is set running for another presettable time t2. In the example shown the contact is made using a small magnet on the lid and a reed switch mounted on the cistern. The rest is straightforward: IC2, the familiar 555, forms a timer whose period can be adjusted up to approximately 10 to 12 minutes using P2. This determines the fan running time. There are three CMOS NAND gates (type 4093) between the reed switch and the timer input which generate the required trigger signal. When the lid is in the ‘up’ position the reed switch is closed.

Capacitor C1 charges through P1 until it reaches the point where the output of IC1a switches from logic 1 to logic 0. The output of IC1b then goes to logic 1. The edge of the 0-1 transition, passed through the RC network formed by C2 and R2, results in the output of IC1c going to logic 0 for a second. This is taken to the trigger input on pin 2 of timer IC2, which in turn switches on the relay which causes the fan to run for the period of time determined by P2. The circuit is powered from a small transformer with a secondary winding delivering between approximately 8 V and 10 V. Do not forget to include a suitable fuse on the primary side.

The circuit around IC1b and IC1c ensures that the fan does not run continuously if the toilet seat lid is left up for an extended period. The time constant of P1 and C1 is set so that the fan does not run as a result of lavatorial transactions of a more minor nature, where the lid is opened and then closed shortly afterwards, before C1 has a chance to charge sufficiently to trigger the circuit.

With this simple circuit that you will be able to control the speed of a DC fan according to the temperature measured by a temperature sensor. It is an ideal accessory for your projects that require cooling that are not constant. 

This simple design allows precise speed control of motors, fans, and blowers, proportional to the temperature. An NTC thermistor (R1) is used as temperature sensor. A circuit optional was added to remotely monitor the operation of the fan and to allow some kind of indication of the approximate speed by increasing the brightness of an LED.

The R5 must be configured to allow the engine just starting to run at the desired temperature. Any 6K8 between the NTC thermistor 22K can operate provided that the R2 value is one tenth of the thermistor. R6, R7 and D1 are optional: R7 obligation is adjusted until the LED glow dimly when the engine is just running.

Parts List
R1 15K @ 20 ° C NTC Thermistor (See Notes)
R2 1K5 1/4W Resistor (See Notes)
R3 1K 1/4W Resistor
R4 270R 1/4W Resistor 1/2W
R5 22K Trimpots
R6 680R 1/4W Resistor (Optional, see Notes)
R7 470R Trimpots
C1 100μF 25V Electrolytic Capacitor
LED D1 (Optional, any shape and color, see Notes)
Q1 BC547 45V 100mA NPN Transistor
Q2 BD140 80V 1.5A PNP Transistor
M1 Fan Motor 12V 700mA max.

Exhaustion fan is a very important element in kitchens. Here may be a easy circuit to manage kitchen fans by monitoring the ambient temperature. its engineered round the renowned precision integrated temperature sensor chip LM35 (IC1). remainder of the circuit may be a non-traditional electromagnetic relay driver wired round the fashionable LED driver LM3914 (IC2). User will switch 3 presetted temperature levels employing a jumper/slide switch (JP1), that determines the warmth level to activate the relay and hence the electrical exhaustion fan wired through the relay contacts. It works off 12V DC power offer.

Only one adjustment is needed during this kitchen Exhaustion fan controller circuit. when construction, set jumper purpose in its 1st position, ie base terminal of T1 is connected to pin thirteen of IC2 and alter the preset P1 fastidiously in order that relay RL1 is energised when ambient temperature level reaches close to 29oC. but this is often not terribly vital as youll choose any threshold level by connecting the jumper points to alternative unused output pins of IC2 (here solely three outputs are used).

An electronic switch that can be used to switch on both the air-conditioner as well as fan of your room, one by one. The schema consists of power supply and control sections. The power supply section is built around transformer X1, bridge rectifier BR1 and filter capacitor C1. The 50Hz, 230V AC mains is stepped down by transformer X1 to deliver a secondary output of 9V, 300 mA. The transformer output is rectified by the bridge rectifier and filtered by capacitor C1.

Control Switch for Fan and Air-Conditioner  Circuit Diagram

When the mains is switched on for the first time, pin 3 of IC CD4017 (IC1) goes high and relay RL1 energies to switch on the fan. When mains is briefly switched off using S1 and then switched on, the power to IC1 is maintained by the charge on capacitor C1. At the same time, there is a trigger pulse on the clock input (pin 14) of IC1, which advances the decade counter and relay RL2 energies to switch-on the air-conditioner. Both the air-conditioner and the fan will be turned off if the switch is in the ‘off’ position.

Assemble the schema on a general-purpose PCB and enclose in a suitable case. Fix the unit onto the switchboard. Use relays RL1 and RL2 with proper contact ratings. The current rating depends on the load that you are going to control.

This schema will turn on/off 12V DC fan or CPU fan when temperature above normal temperature.You can set turn on temperature by adjust VR1. This schema use an NTC (Negative temperature coefficient)which is a thermistor is one in which the zero-power resistance decreases with an increase in temperature. So If temperature increate the voltage at pin 3 on LM311 will decreated .The resistance of NTC is about 10K at 25c.

VR1 should be multi-turn potentiometer type such 10K/25 turn