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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.  Fan Speed ​​Control for Temperature Circuit Diagram 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 No...

A very simple DC motor speed controller circuit can be constructed using a LM317 voltage regulator integrated circuit. This DC motor speed controller can be used for speed control  of mini drills or for other small DC motors. This motor controller circuit will provide a large output current. The maximum output current from the secondary turns of the transformer shout provide 1.5 times of the maximum DC output current. The output voltage and the speed (rpm) is set by the P2 variable resistor. DC Motor Speed Controller using a LM317:  As soon as the current drawn exceeds a certain value, T2 will be switched on. This results in a base current for T3 so that R5 is in parallel with R6. This automatically raise the output voltage to counter a threatened drop in rpm.  The moment at which this action occurs is set by P1.

VARIABLE PWM SPEED CONTROL

There are several methods for controlling the speed of DC motors. One simple method is to add series resistance using a rheostat. As considerable power is consumed in the rheostat, this method is not economical. Another method is to use a series switch that can be closed/opened rapidly. This type of control is termed as chopper control. We’ve described here a PWM-based chopper circuit that smoothly controls the speed of general-purpose DC motors. Fig.1: Block diagram of PWM-based speed controller Fig. 1 shows the block diagram of a basic PWM-based chopper. The circuit shown in Fig. 2 is designed as per this diagram. A dual timer IC (NE556) is used to configure both the astable as well as the monostable multivibrator. Timing components for the astable are chosen to provide a frequency of 546 Hz, while the monostable components are selected to obtain a maximum pulsewidth of 2.42 ms. Diode D1 improves duty factor of the astable oscillator output, whereas D2 acts as a free-wheeling diode. ...

DC Motor Speed Control using PWM The so-called PWM or Witdh modulation is a technique often used to control a load, for example, is the control of DC motor speed PWM techniques are used frequently. Usually to make a simple PWM (for practice or the introduction PWM) fans to use some of the facts of the op-amp circuit, which consists of Schmitt Trigger circuit, the integrator and comparator. Schmitt Trigger function that produces a square wave will become the sawtooth wave or integrator is also called common rail and the ramp compared to a reference voltage that can change a lot of stress. So the result is a PWM output. These two schemes are variations of different circuit PWM. The diagrams are for 12V operation and there are upper (ground) and low side (+12 V common) versions. The version of the lower circuit uses an N-channel FET, the high-side version of the circuit uses a P-channel FET. N channel devices tend to handle more current P-channel devices, which are also less expen...

The effect can be eliminated by means of Ri compensation, which essentially entails measuring the motor’s current consumption, relating this to the motor’s instantaneous drop i across Ri, and increasing the supply voltage accordingly. The load current is measured as the drop across sensing resistor R3. For optimum results, this impedance must be kept about equal to that of the motor. Figure 2 shows the practical circuit of the motor driver based on a power operational amplifier . Simple DC operated motors with a permanent magnetic stator behave as an independently energized motor. The speed of an ideal motor with an, infinitely low internal resistance is in direct proportion to the voltage applied, irrespective of the torque. The motor thus runs at a speed at which its reverse electromotive force (e.m.f.) equals the supply voltage. The reverse e.m.f. is directly proportional to the force of the (constant) magnetic field , and the motor speed. In theory, therefore, the motor speed can...

The UCC27518 and UCC27519 single-channel, high-speed, low-side gate driver device is capable of effectively driving MOSFET and IGBT power switches. Using a design that inherently minimizes shoot-through current, UCC27518 and UCC27519 are capable of sourcing and sinking high, peak-current pulses into capacitive loads offering rail-to-rail drive capability and extremely small propagation delay typically 17 ns. The UCC27518 and UCC27519 provide 4-A source, 4-A sink (symmetrical drive) peak-drive current capability at VDD = 12 V. The UCC27518 and UCC27519 are designed to operate over a wide VDD range of 4.5 V to 18 V and wide temperature range of -40°C to 140°C. Internal Under Voltage Lockout (UVLO) circuitry on VDD pin holds output low outside VDD operating range. Features Low-Cost, Gate-Driver Device Offering Superior Replacement of NPN and PNP Discrete Solutions Pin-to-Pin Compatible With TI’s TPS2828 and the TPS2829 4-A Peak Source and 4-A Peak Sink Symmetrical Drive Fast Propagati...

A partial solution to quietening noisy PCs can be to reduce the speed of internal cooling fans. Low-cost fan speed controllers are available, but they often employ inefficient, heat-generating linear regulators and contain no temperature feedback mechanism. This idea makes use of a readily available, cheap in-car mobile phone charger. The majority of these use common circuitry and require only minor modifications to operate as efficient fan speed controllers complete with temperature feedback. Most in-car chargers are based on the well-known MC34063 DC-DC switchmode IC. When used for charging mobile phones, the open-circuit output voltage is typically set to between 7V and 9V. This is achieved with a simple voltage divider across the output, the centre point of which connects to the feedback input (pin 5) of the MC34063. To make the output voltage var-iable with air temperature, first replace the upper resistor of the divider with a 4.7kΩ resistor in series with a 4.7kΩ trimpot. The lo...