Skip to main content

Simple DC Fan Controller


This circuit is ideal to control the cooling fan of heat generated electronic gadgets like power amplifiers. The circuit switches on a fan if it senses a temperature above the set level. The fan automatically turns off when the temperature returns to normal.

The circuit uses an NTC (Negative Temperature Coefficient) Thermister to sense heat. NTC Thermister reduces its resistance when the temperature in its vicinity increases.IC1 is used as a voltage comparator with two potential dividers in its inputs. Resistor R1 and VR1 forms one potential divider connected to the non inverting input of IC1 and another potential divider comprising R2 and the 4.7K Thermister supplying a variable voltage to the inverting input of IC1. VR1 is adjusted so as to give slightly lesser voltage at the non inverting input than the inverting input at room temperature.

DC Fan Controller Circuit Diagram

In this state, output of IC1 will be low and the Fan remains off. When the temperature near the Thermister increases, its resistance decreases and conducts. This drops the voltage at pin 2 of IC1 and its output becomes high. T1 then triggers and fan turn on. Red LED indicates that fan is running. Capacitor C1 gives a short lag before T1 turns on to avoid false triggering and to give proper bias to T1.DC fan can be the one used in Computer SMPS.

Keep the Thermistor near the heat sink of the Amplifier PCB and switch on the amplifier for 10 minutes. Then adjust VR1 till the Fan stop running.When the temperature rises, Fan will automatically switch on. 
Sourced by :

Labels:

Comments

Post a Comment

Popular posts from this blog

Mantis 9 1 CNC Mill

The Mantis 9.1 design is a radical departure from version 8 and earlier. Most notably, the part count has been almost halved! The current design has 13 parts, all of which can be made with a handsaw and a drill press. Also, I’ve traded away my alignment free exactly-constrained design for extra stiffness. Several unsuccessful attempts to eradicate the last of the slop in the Z axis on version 8 lead me back to the world of over-constrained parallel rods. My previous attempts at an over-constrained design (versions 1-5) all failed because I was unable to make the rods sufficiently parallel to avoid jamming. What to do? [ ]
Post a Comment
Read more

25 Watt Audio Amplifier Circuits Diagram

25 Watt Audio Amplifier Circuits Diagram Parts: R1 ,R4 _________47K   1/4W Resistors R2____________ 4K7   1 /4W Resistor R3____________ 1K5   1 /4W Resistor R5__________390R    1/4W Resistor R6__________470R    1/4W Resistor R7___________33K    1/4W Resistor R8__________150K    1/4W Resistor R9___________15K    1/4W Resistor R10__________27R    1/4W Resistor R11_________500R    1/2W Trimmer Cermet R12 ,R13,R16 __10R    1/4W Resistors R14 ,R15 _____220R    1/4W Resistors R17___________8R2     2W Resistor R18____________R22    4W Resistor ( wirewound )   C1___________ 470nF   63V Polyester Capacitor C2___________ 330pF   63V Polystyrene Capacitor C3 ,C5 ________470µF   63V Electrolytic Capacitors C4 ,C6,C8,C11 _100nF   63V Polyester Capacitors C7___________100µ F   25V Electrolytic Capacitor C9____________ 10pF   63V Polys...
Post a Comment
Read more

Electronic Extended Play Circuit Diagram

This is a Electronic Extended Play Circuit Diagram. A single op amp-one of four contained in the popular LM324-is operating in a variable pulse width, free-running square wave oscillator circuit, with its timed output driving two transistors that control the on/ off cycle of the tape-drive motor. The Oscillator` s positive feedback path holds the secret to the successful operation of the variable on/ off timing signal.   Electronic Extended Play Circuit Diagram The two diodes and pulse width potentiometer R8 allows the setting of the on and off time, without affecting the oscillator`s operating frequency. One diode allows only the discharge current to flow through it and the section of R8 that it`s connected to. The other diode, and its portion of R8, sets the charge time for the timing capacitor, C3. Since the recorder`s speed is controlled by the precise off/on timing of the oscillator, a simple voltage-regulator circuit (Ql, R3, and D4) is included.  Connecting the spe...
Post a Comment
Read more