This is the digital fan speed control circuit design that can be utilize to control the speed of 220V fans using induction motor. The speed control is nonlinear, i.e. in steps. The current step number is displayed on a 7-segment display. Speed can be varied over a wide range because the circuit can alter the voltage applied to the fan motor from 130V to 230V RMS in a maximum of seven steps.

How the Digital Fan Speed Control Circuit Work

The triac used in the final stage is fired at different angles to get different voltage outputs by applying short-duration current pulses at its gate. For this purpose a UJT relaxation oscillator is used that outputs sawtooth waveform. This waveform is coupled to the gate of the triac through an optocoupler (MOC3011) that has a triac driver output stage.

The pedestal voltage control is used for varying the firing angle of the triac. The power supply for the relaxation oscillator is derived from the rectified mains via 10 Kohm, 10W series dropping/limiting resistor R2.

The pedestal voltage is derived from the non-filtered DC through optocoupler 4N33. The conductivity of the Darlington pair transistors inside this optocoupler is varied for getting the pedestal voltage. For this, the positive supply to the LED inside the optocoupler is connected via different values of resistors using a multiplexer (CD4051).

The value of resistance selected by the multiplexer depends upon the control input from BCD up-/down-counter CD4510 (IC5), which, in turn, controls forward biasing of the transistor inside optocoupler 4N33. The same BCD outputs from IC5 are also connected to the BCD-to-7-segment decoder to display the step number on a 7-segment display.

NAND gates N3 and N4 are configured as an astable multivibrator to produce rectangular clock pulses for IC5, while NAND gates N1 and N2 generate the active-low count enable (CE) input using either of push-to-on switches S1 or S2 for count up or count down operation, respectively, of the BCD counter.

Optocoupler 4N33 electrically isolates the high-voltage section and the digital section and thus prevents the user from shock hazard when using switches S1 and S2. BCD-to-7-segment decoder CD4543 is used for driving both common-cathode and common-anode 7-segment displays. If phase input pin 6 is ‘high†the decoder works as a common-anode decoder, and if phase input pin 6 is “low” it acts as a common-cathode decoder.

Optocoupler 4N33 may still conduct slightly even when the display is zero, i.e. pin 13 (X0, at ground level) is switched to output pin 3. To avoid this problem, adjust preset VR1 as required using a plastic-handled screwdriver to get no output at zero reading in the display.

Digital Fan Speed Control Source: EFY Mag 11/2001

This is the circuit design of unipolar stepper motor driver to control unipolar stepper motors with 5, 6 or 8 wires. It uses four MOSFET IRFZ44. This circuit can be operated in free-standing or PC-controlled mode.

Unipolar Stepper Motor Driver Mode

In free-standing mode an internal square-wave oscillator based on IC2:B of the 4093 supplies timing pulses to the OSC output. The frequency of these pulses and thus the speed of the stepper motor is controlled by the trimpot VR1 (100K.) A series 1K resistor controls the maximum frequency. You may increase the value of this resistor for your own needs. These pulses are fed into the STEP input which is buffered and inverted by IC2:D. This helps prevent false triggering. Similarly, IC2:C buffers and inverts the DIRection input. A SPDT taking the input to +5VDC or ground controls the direction of rotation.

IC3:C and D (4030 or 4070 exclusive OR gates) invert the outputs available at Q and /Q outputs of each of the flip-flops (FF) IC4:A and IC4:B. The incoming step-pulses clock the FF, thus toggling the Q & /Q outputs and this turns the MOSFETâ€s on and off in sequence. The IRFZ44â€s have a low on-resistance and can deliver up to 6A each without needing a heatsink.

Power to the stepper motor is connected to V+ and GND terminals as shown on the overlay. There is a separate power supply, KITV, to the 78L05 to power the ICâ€s. 9V ??” 12VDC will be sufficient. R2/C2 form a low-pass filter to filter fast-rise switching transients from the motor.

Note that some stepper motor texts say to use a 4070 instead of a 4030. We have not worked out why this is. Certainly our testing with the 4030â€s showed no problems. I would like to hear from anyone who knows why this advice is sometime given.

In computer-controlled mode use the three pads with pins DIR, STEP and GND. Switch the SPDT switch to EXTernal. The direction SPDT has no effect in external mode.

Kit for this unipolar stepper motor driver is available:

Download kit PDF manual (schematic, part list, explanation included):

PDF Manual Unipolar Stepper Motor Driver Kit

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This bipolar stepper motor driver circuit will drive a bipolar stepper motor using externally supplied 5V levels for stepping and direction. These usually come from software running in a computer or from a microcontroller unit. The circuit uses IRFZ44 and MTP2955 MOSFETâ€s.

All the power inputs were connected together. The CLOCK was connected to STEP, and the RESET was connected to DIRection. Pushing the CLOCK button then advanced the motor one notch. Pressing CLOCK with the RESET button also depressed and pressed down advanced the motor one notch the other way.

Bipolar Stepper Motor Driver Part Lists

Resistors 1/2W
R1, R2 : 1K
R3, R4 : 10K
R5, R6, R11, R12 : 12K
R7, R8, R13, R14 : 2K2
R9, R10, R15, R16 : 150R
C1 : 100uF/63V ecap
C2 : 10uF mini ecap
C3 : 100nF
D1-D8: 1N4148 diode
IC1 : 4013
IC2 : 4030
IC3, IC4 : 4N25
IC5 : 7805

Bipolar stepper motors have two coils and are controlled by changing the direction of the current flow through the coils in the proper sequence. These motors have only four wires.

The unipolar stepper motor is connected as a bipolar motor (the 2 center wires of the 6 wire motor are unused.) 9V was used. The STEP and DIRection negative inputpins were tied together and connected to system ground.

Kit for this bipolar stepper motor driver circuit is available.

Download kit manual in PDF:

Bipolar Stepper Motor Driver Manual Kit

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This is the simple and low cost pulse width modulation – PWM DC motor controller using a MOSFET. This kind connection for DC motor control is to prevent heat and minimize the power consumption. It controls the motor speed by driving the motor with short pulses. These pulses vary in duration to change the speed of the motor. The longer the pulses, the faster the motor turns, and vice versa.

PWM DC Motor Controller Component List

• R1 1 Meg 1/4W Resistor
• R2 100K Potensiometer
• C1 0.1uF 25V Ceramic Disc Capacitor
• C2 0.01uF 25V Ceramic Disc Capacitor
• Q1 IRF511 MOSFET or IRF620
• U1 4011 CMOS NAND Gate
• S1 DPDT Switch
• M1 Motor (See circuit notes)
• MISC Case, Board, Heatsink, Knob For R2, Socket For U1

PWM DC Motor Controller Circuit Notes

• R2 potensiometer to vary the speed of the oscillator and therefore the speed of M1.
• M1 can be any DC motor that operates from 6V and does not draw more than the maximum current of Q1. The voltage can be increased by connecting the higher voltage to the switch instead of the 6V that powers the oscillator. Be sure not to exceed the power rating of Q1 if you do this.
• Mount a heatsink on Q1 MOSFET.
• Q1 in the parts list can handle a maximum of 5A. Use the IRF620 for 6A, if you need any higher.

There are many version of stepper motor type, also the many version of stepper motor controller design. This circuit is a general-purpose stepper motor controller that use IC TDA2030 as the driver. This circuit can be used with a wide range of operating voltages, from approximately 5 V to 18 V. It can drive the motor with a peak voltage equal to half the supply voltage, so it can easily handle stepper motors designed for voltages between 2.5 V and 9 V.

The circuit which come from Elektor Electronics Magazine (Author: Gert Baars), can also supply motor currents up to 3.5 A, which means it can be used to drive relatively large motors. The circuit is also short-circuit proof and has built-in over temperature protection. Two signals are required for driving a stepper motor. In logical terms, they constitute a Grey code, which means they are two square-wave signals with the same frequency but a constant phase difference of 90 degrees.

IC1 generates a square-wave signal with a frequency that can be set using potentiometer P1. This frequency determines the rpm of the stepper motor. The Grey code is generated by a decimal counter in the form of a 4017. Outputs Q0?Q9 of the counter go high in succession in response to the rising edges of the clock signal. The Grey code can be generated from the outputs by using two OR gates, which are formed here using two diodes and a resistor for each gate, to produce the I and Q signals.

Here “I” stands for “in-phase” and “Q” for “quadrature”, which means it has a 90-degree phase offset from the I signal. It is common practice to drive the windings of a stepper motor using a pair of push-pull circuits for each winding, which is called an “H bridge”. That makes it possible to reverse the direction of the current through each winding, which is necessary for proper operation of a bipolar motor (one whose windings do not have centre taps).

Of course, it can also be used to properly drive a unipolar motor (with centre-tapped windings). Instead of using a push-pull circuit of this sort, here we decided to use audio amplifier ICs (type TDA2030), even though that may sound a bit strange. In functional terms, the TDA2030 is actually a sort of power opamp. It has a difference amplifier at the input and a push-pull driver stage at the output.

IC3, IC4 and IC5 are all of this type (which is economically priced). Here IC3 and IC4 are wired as comparators. Their non-inverting inputs are driven by the previously mentioned I and Q signals, with the inverting inputs set to a potential equal to half the supply voltage. That potential is supplied by the third TDA2030. The outputs of IC3 and IC4 thus track their non-inverting inputs, and each of them drives one motor winding.

The other ends of the windings are in turn connected to half the supply voltage, provided by IC5. As one end of each winding is connected to a square-wave signal that alternates between 0 V and a potential close to the supply voltage, while the other end is at half the supply voltage, a voltage equal to half the supply voltage is always applied to each winding, but it alternates in polarity according to the states of the I and Q signals.

That”s exactly what we want for driving a bipolar stepper motor. The rpm can be varied using potentiometer P1, but the actual speed is different for each type of motor because it depends on the number of steps per revolution. The motor used in the prototype advanced by approximately 9? per step, and its speed could be adjusted over a range of approximately 2 to 10 seconds per revolution.

In principle, any desired speed can be obtained by adjusting the value of C1, as long as the motor can handle it. The adjustment range of P1 can be increased by reducing the value of resistor R5. The adjustment range is 1:(1000 + R5)/R5, where R5 is given in k.If a stepper motor is switched off by removing the supply voltage from the circuit, it”s possible for the motor to continue turning a certain amount due to its own inertia or the mechanical load on the motor (flywheel effect).

It”s also possible for the position of the motor to disagree with the states of the I and Q signals when power is first applied to the circuit. As a result, the motor can sometimes “get confused” when starting up, with the result that it takes a step in the wrong direction before starting to move in direction defined by the drive signals. These effects can be avoided by adding the optional switch S1 and a 1-k resistor, which can then be used to start and stop the motor. When S1 is closed, the clock signal stops but IC2 retains its output levels at that moment, so the continuous currents through the motor windings magnetically “lock” the rotor in position.

The TDA2030 has internal over temperature protection, so the output current will be reduced automatically if the IC becomes too hot. For that reason, it is recommended to fit IC3, IC4 and IC5 to a heat sink (possibly a shared heat sink) when a relatively high-power motor is used. The tab of the TO220 case is electrically bonded to the negative supply voltage pin, so the ICs can be attached to a shared heat sink without using insulating washers.

One 555 (IC1:B) is set up as an astable oscillator. The output frequency of the trigger pulses is specified by:

f = 1.44 / ((R3 + 2R4)C2), or about 410Hz.

The time period for the high output is specified by

THIGH = 0.69(R3 + R4)C2 seconds.

And, the low output by T_LOW = 0.69R4C2 seconds. The 2nd 555 (IC1:A) is set up for Pulse Width Modulation. It will be build in monostable mode. It is triggered using the continuous pulse train from the first 555 timer. Nevertheless, by also applying a DC voltage to pin 3, the comparator reference levels are going to be modified from their nominal levels of one-third & two-thirds of the supply voltage. This has the effect of modulating the pulse width as the control voltage varies. The control voltage is supplied via transistor Q1, which is configured as an emitter-follower. This means that the emitter output voltage follows the base input voltage (less 0.6 volt base-emitter drop). This configuration gives us a low output impedance voltage source with which to drive the control input of the timer. This makes the control voltage less susceptible to the loading effect of the timer control input.

The output from the timer is a continuous stream of pulses whose width is controlled by the voltage level used on the control voltage input. This modulated output drives a MOSFET, Q2, that is applied to switch the voltage to the DC motor.

Components List:

R1 = 560R
R2 = 470R
R3 = 33K
R4, R7 = 2K2
R5 = 10K
R6 = 10R
P1 = 500R (501) Koa trimpot
RV1 = 10K potensiometer
D1 = 1N4004
C1 = 10uF/50V
C2, C3, C4, C5, C6, C7 = 100nF
C8 = 100uF/25V
IC1 = Nmos LM/NE556
Q2 = IRF530 mosfet
Q1 = BC547 Transistor

Technical Details:

• Uses NE556 to pulse-width modulate IRF530N MOSFET.
• DC Motor Speed Controlled via a potentiometer.
• Speed control for DC motors up to 100 Volts @ 7.0Amps without sacrificing motor torque.
• This DC Motor controller can handle up to 16 Amps, but PCB trace capacity would have to be beefed up with some hookup wire where DC motor current runs through the Printed Circuit Board.
• Requires operating voltage of 5 – 16 VDC.

You can buy the circuit from electronickits.com

Download the manual including the circuit diagram, parts list and the complete explanation (PDF file):

DC Motor Controller Project Kit

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Bruce Robinson explaination about this circuit:

• I did a few revised drawings for Ian quite a while back, so he could place them up at beam-online. However, they did not get posted inside the midst of the a lot of revisions he was doing.
• Attached (begging Ian’s indulgence), will be the two versions of the circuit, one which turns on having a Positive input, the other (for quadcores) having a Negative input.
• Ian shows 100k input resistors. I’ve been applying 47k resistors with success. Tilden’s report recommends nothing lower than 50k (I assumed 47k was near enough) and up to 20 Meg or so.
• I’ve also observed a slight drop in speed when I use these bridges, but only about 10% or so.

Technical details:

• Until 800 mA capacity (working with PN2222 and PN2907 transistors)
• Not “smoke-proof” (i.e., it cannot deal with drive voltage in both directions at once)
• 30 connections per bridge (so, 30 holes in case you make a PCB)

Original Tilden H-Bridge article can be found here. Read the article for detailed ecplanation and recommendation.

The above diagram is the schematic diagram of an electronic motor starter circuit. This motor starter protects singlephase motors against voltage fluctuations and overloading. Its salient function is a soft on/off electronic switch for simple operation.

The transformer steps down the AC voltage from 230V to 15V. Diodes D1 and D2 rectify the AC voltage to DC. The unregulated power supply is given towards the protection circuit. Inside the protection circuit, transistor T1 is utilized to defend the motor from over-voltage.

The over-voltage setting is performed working with preset VR1 such that T1 conducts when voltages goes beyond upper limit (say, 260V). When T1 conducts, it switches off T2. Transistor T2 works as the under-voltage protector. The under-voltage setting is performed using the support of preset VR2 such that T2 stops conducting when voltage is below lower limit (say, 180V). Zener diodes ZD1 and ZD2 deliver base bias to transistors T1 and T2, respectively. Transistors T3 and T4 are connected back to back to form an SCR configuration, which behaves as an “on”/”off” control. Switch S1 is utilized to turn on the pump, whilst switch S2 is utilized to turn off the pump.

Whilst generating over-/under-voltage setting, disconnect C2 temporarily. Capacitor C2 prevents relay chattering because of rapid voltage fluctuations.

Regulator IC 7809 provides the 9V regulated supply to soft switch along with the relay after filtering by capacitor C4. A appropriate miniature circuit breaker is utilized for automatic over-current protection. Green LED (LED1) indicates that the motor is “on” and red LED (LED2) indicates that the power is “on”. The motor is connected towards the normally-open contact of the relay. When the relay energises, the motor turns on.

This electronic motor starter circuit is already tested and available in PDF version. Download the circuit and explanation in PDF file: Electronic Motor Starter circuit

This is a DC motor controller circuit, built using transistor TIP31 based on H-Bridge concept. The switch S1 and S2 are normally open , push to close, press button switches. The LED function is to indicate the direction of motor rotation, you may use any common LED type. The TIP31 transistors capable to handle 3A maximum electric current, you may change the transistors for DC motors with higher current consumption. Remember, running under load draws more current.

Actually, this circuit was built to drive a small DC motor and can be used for small application such as automatic closing and opening systems, mobile robot actuator, small fan, etc. The four diodes arround the DC motor are back EMF diodes. The diode type is depended of the DC motor current consumption. For a 12V motor drawing 1A under load, use 1N4001 diodes. For 3A DC motor, then use IN5401.

Resistor R1 biases the potentiometer to match the input range of U1. Full counter-clockwise rotation of the pot corresponds to maximum-speed reverse rotation of the motor. Mid-scale on the pot corresponds to motor off, and full clockwise rotation of the pot produces maximum-speed forward rotation in the motor.

The characteristics of a given motor may allow you to eliminate the amplifier’s output filter (L1, L2, C1, and C2). But, unless the control circuitry shown is located near the motor, you should include the filter to reduce EMI.

Download more explanation about the circuit diagram of motor speed control with MAX4295 in PDF version:
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