Electronic Circuits Free

Home Electric Circuits

2018-09-25T10:05:00.000-07:00

Electric energy required to operate home electric appliances is obtained from the

national electric grid. Electric energy generated by electric power stations are

raised to high voltages such as 132 kV or 220 kV using step-up transformers and

distributed throughout the island. In distribution sub-centres, these high voltages

are lowered to voltages such as 33 kV or 11 kV and ultimately they are lowered

down to 230 V or 110 V before supplying to households. Electricity provided to houses is in

the form of an alternating current with a frequency of 50 Hz for 230 V and 60 Hz for 110 V

A – Distribution wire B – Supply cable

C – Overload circuit breaker (or Service fuse) D – Electric meter

E – Isolator (or Main fuse with main switch) F – Residual current circuit

breaker or trip switch (RCCB)

G – miniature circuit breakers or fuses (MCB) H – Switch

I – plug socket J – Earth wire

K – Light bulb

Electricity is supplied to houses using a service cable consisting of two wires known

as the live wire and the neutral wire. The current flowing through these two wires

is provided to the electric appliances through a circuit inside the house.

Efficiency of electric appliances and conserving power

2018-09-25T09:28:00.000-07:00

In many instances, the same purpose can be achieved using various different

appliances. In order to get illumination we can use filament bulbs, fluorescent

light tubes or CFL lights (compact fluorescent lights). Choosing a more efficient

appliance helps us to save energy. A few different types of bulbs giving the same

illumination, their power output and life times are given in Table

According to Table, it is advantageous to use LED bulbs as light sources.

However, the use of good quality LED bulbs is limited due to their high initial cost.

Similarly, the efficiencies of cookers used to prepare food are different from one to

another due to varying amounts of heat wastage. Old cookers that use heating coils

are the lowest in efficiency. Emersion heater is highly efficient for heating water.

The reason is that, all the heat generated in the heater is transferred to water when

using it. Heaters which contains hot plates such as rice cooker is more efficient

because heat loss is less from them. Although microwave ovens cannot be used

to cook all types of food, they are very efficient since they produce heat inside the

food items. In addition to these, induction cookers with high efficiencies are now

available in the market. In these devices, the variable magnetic field emitted by the

cooker generates heat only at the bottom of the cooking utensil.

For Extra Knowledge:

The power consumption of television sets that use LCD screens is lower than that

of the old televisions that use cathode ray tubes. LCD television sets that use LED

lights to illuminate the screen have a very low power consumption and are known

as LED televisions in the market.

Similarly, it is more efficient to use table fans to cool houses than ceiling fans.

Using the most efficient device suitable for a particular purpose whenever possible

would help to minimize the future energy crisis.

If 40% of the energy supplied to a certain electric appliance is lost as heat, then

only 60% of the energy would be used for the expected purpose. This means that

the efficiency of the electric appliance is 60%. We should try to minimize the loss

of electric energy as heat and get the maximum out of the electric energy supplied

for a particular purpose. Ironing all clothes required for a week in one occasion is

more efficient because it saves electricity used in the initial heating of the iron. All

the unwanted lights of the home should be switched off. Also, you have to use more

efficient bulbs such as CFL and LED bulbs.

Power output of an electric appliance

2018-09-21T09:34:00.003-07:00

We know that power is the work done in a unit time.

Just like in mechanical work, power is the rate of doing work in work done by

electricity too. That is, power is the work done in a unit time or the energy consumed

in a unit time.

Therefore the rate of energy consumption P by an electric appliance operated with

a voltage V and drawing a current I is given by the following equation.

Power = voltage ×current

P = VI

When the voltage, V is measured in Volts (V) and the current, I in Amperes (A) the

power, Pis given in Watts (W).

Example 1

When a filament bulb is connected across a voltage difference of 12 V, a current of

2 A flows through it. What is the power of the bulb?

Power P= VI

= 12× 2 W

P= 24 W

Power of the bulb is 24 W.

Example 2

An electric oven operates under a 230 V power supply. If it has a power output of

2000 W, find the current drawn when the oven is working.

P = VI

∴ 2000 = 230× I

∴ I =

2000

230

= 8.69 A

The current drawn by the oven is 8.69 A.

In the heating coils (heating element) of electric ovens, the energy consumed is

converted only into heat. In some other appliances, part of the electric energy

is converted into heat due to their internal resistance, while the remaining part is

converted into other forms of energy.

Power and Energy of Electric Appliances

2018-09-21T09:10:00.000-07:00

We use electric energy to do various jobs in our daily lives conveniently. On all

these occasions we convert electric energy into another form of energy to suit our

requirements. This energy conversion takes place in various electric appliances.

The instruments used for these energy conversions are known as electric appliances.

The main forms of energy conversions that take place in some electric appliances

used in daily life are given in the Figure

In some electric appliances, after the first energy conversion, another energy

conversion also takes place and we use that energy. As an example, in a filament

bulb, electric energy is initially converted into heat which increases the temperature

of the filament resulting in the emission of light. In fluorescent lights electric energy

is first converted into ultraviolet radiation which is next converted into visible light.

Adjustable Voltage Regulator | 15V 10 Amp Adjustable Voltage Regulator Circuit Using IC LM196

2013-05-06T22:44:00.000-07:00

The below article explains a linear voltage regulator circuit using the IC LM196 which is capable of handling up to 10 Amps of current and is able to provide a variable output right from 1.25V to 15V DC.
The IC LM 196 is single chip versatile, high performance regulator device which can be configured to provide an adjustable voltage output of 1.25V to 15V or even further at currents in excess of 10 amps.
It is a single chip solution for all electronic circuit applications which involve or require regulated DC up to 10 amps.

That means now you can carry on heavy duty voltage operations as per your personal preference using this easy to build single chip circuit
Many of my earlier posts have discussed circuits involving a similar IC, the LM338, which is also capable of providing similar features, but cannot handle above 5 amps, the LM196 on the other hand overcomes this limitation of LM338 and goes further by adding 5 amps more to the specs.

The main features of this adjustable 15V 10 amp voltage regulator IC may be summarized as follows:

Output custom tailored at +/-0.8V

Minutely adjustable voltage right from 1.25V to 15V DC

Guaranteed output current that's not below 10 amps

Verified with P+ product enhancement testing

Maximum power dissipation not exceeding 70 watts even at full load.

Output internally protected against over load and short circuit

Device internally protected against thermal run away or thermal break down situations.

Output voltage supply guaranteed even under worst case scenarios such as adjustment pin disconnected.

Pin out details of LM196

As given in the following diagram, from bottom with the larger area of the metal downward, the pin outs of the IC LM196 may be identified as follows:

Right pin = Adjustment pin

Left Pin = Output pin.

Case or Body = Input

The standard 10 amp voltage regulator circuit diagram using the IC LM196 can be witnessed in the following figure.

The calculations of the resistors are similar to that of IC LM338 or LM317. R2 may be adjusted to get the required regulated voltage at the output.
All the ground terminals involved in the circuit must be fixed with the main input ground which will be obviously the negative point of the bridge rectifier (not shown here). Similarly, the positive to the load must be directly acquired from the relevant lead of the IC.
The ground and the positive is taken from the main nodes due to the involvement of high currents with the circuit. As current increases, the conductor proportionately offers more resistance to the flow of the current which results in voltage drops at the output and hence unnecessary lengths of tracks should be avoided.

Flash an LED | Flash an LED directly from from AC mains power

2013-02-07T23:11:00.001-08:00

LED technology is opening the door to a variety of high-power-illumination applications. The circuit in Figure 1 can let you know when ac power is available. To drive a power LED from the ac line requires a converter or a similar arrangement. In this circuit, a passive dropper greatly simplifies the total design. You can also simplify the circuit to run on dc power, which lets you use it from automotive batteries to supply light at night.

The design comprises an inrush-limiting resistor, R1; a half-wave rectifier with a filtering capacitor comprising D2, D3, D4, and C2; a relaxation oscillator; and two high-power LEDs. Because the circuit drives the LED with a constant current, you can use any LED color to suit the situation.

The circuit uses a simple DIAC (diode-alternating-current) relaxation oscillator, which activates a constant-current switching circuit comprising IC2 and Q1. The DIAC turns on when capacitor C3 charges through diode D1 and resistor R2 from the mains voltage. After a number of half-cycles of the mains, the voltage on C3 exceeds the break-over voltage of the DIAC, the DIAC conducts, and C3 discharges through R3 and optocoupler IC1. The optocoupler activates the constant-current switching circuit, resulting in a brief, intense flash of light from the LEDs.

Audio Power Amplifier | 36 Watt Audio Power Amplifier Using TDA1562Q

2013-01-04T10:56:00.001-08:00

It's based on a Philips class-H audio amplifier IC and can deliver 36W RMS OR 70W music power, all from a 13.8V supply. Our new Mighty Midget Amplifier can really pack a punch - around 36W RMS continuous into a 4-ohm load when using a 13.8V supply. However, it's the 70W of output power that it can deliver during dynamic (music) signal conditions that really make you sit up and take notice.

As can be seen from the photos and the circuit diagram, the Mighty Midget uses just a handful of parts. It's built on a PC board that measures just 104mm x 39mm but while its size may be modest, these's nothing at all modest about its power output. And the noise and distortion figures are pretty good too.

At the heart of the circuit is the TDA1562Q IC, described by Philips as a "monolithic integrated Bridge-Tied Load (BTL) class-H high-efficiency power amplifier". It comes in a 17-pin "DIL-bent-SIL" plastic package and is not only designed for use in car audio and portable PA work but for mains applications as well; eg, mini/midi audio components and TV sound. At the heart of the circuit is the TDA1562Q IC, described by Philips as a "monolithic integrated Bridge-Tied Load (BTL) class-H high-efficiency power amplifier". It comes in a 17-pin "DIL-bent-SIL" plastic package and is not only designed for use in car audio and portable PA work but for mains applications as well; eg, mini/midi audio components and TV sound.

Performance:

Output power:----------------------36W RMS into 4R
Music power:-----------------------70W into 4R
Frequency response:---------------1dB down at 28Hz and 55kHz
Input sensitivity:-------------------130mV RMS (for 36W into 4?)
Harmonic distortion:----------------typically 0.2% (see graphs)
Signal-to-noise ratio:----------------95dB unweighted (22Hz to 22kHz)

220V Operated 12V fan | 12V Fan Directly Connecting to 220V AC

2013-01-03T10:20:00.000-08:00

This circuit idea is certainly not new, but when it comes to making a trade-of between using a small, short-circuit proof transformer or a capacitive voltage divider (directly from 230 V mains voltage) as the power supply for a fan, it can come in very handy. If forced cooling is an afterthought and the available options are limited then perhaps there is no other choice. At low currents a capacitive divider requires less space than a small, short-circuit proof transformer.

R1 and R2 are added to limit the inrush current into power supply capacitor C2 when switching on. Because the maximum rated operating voltage of resistors on hand is often not known, we choose to have two resistors for the current limit. The same is true for the discharge resistors R3 and R4 for C1. If the circuit is connected to a mains plug then it is not allowed that a dangerous voltage remains on the plug, hence R3 and R4.

Capacitor C1 determines the maximum current that can be supplied. Above that maximum the power supply acts as a current source. If the current is less then zener diode D1 limits the maximum voltage and dissipates the remainder of the power. It is best to choose the value of C1 based in the maximum expected current. As a rule of thumb, start with the mains voltage - when calculating C1.
The 12 V output voltage, the diode forward voltage drops in B1 and the voltage drop across R1 and R2 can be neglected for simplicity. The calculated value is then rounded to the nearest E-12 value. The impedance of the capacitor at 50 Hz is 1 / (2p50C). If, for example, we want to be able to supply 50 mA, then the required impedance is 4600 ? (230 V/50 mA). The value for the capacitor is then 692 nF.
This then becomes 680 nF when rounded. To compensate for mains voltage variations and the neglected voltage drops you could potentially choose the next higher E-12 value. You could also create the required capacitance with two smaller capacitors. This could also be necessary depending on the shape of the available space. It is best to choose for C1 a type of capacitor that has been designed for mains voltage applications (an X2 type, for example).

Motor Speed Controller | PWM Controller for Dimmer or Motor Speed Controller

2012-12-27T00:04:00.000-08:00

This is yet another project born of necessity. It's a simple circuit, but does exactly what it's designed to do - dim LED lights or control the speed of 12V DC motors. The circuit uses PWM to regulate the effective or average current through the LED array, 12V incandescent lamp (such as a car headlight bulb) or DC motor. The only difference between the two modes of operation is the addition of a power diode for motor speed control, although a small diode should be used for dimmers too, in case long leads are used which will create an inductive back EMF when the MOSFET switches off.

Completed PWM Dimmer/Speed Control

The photo shows what a completed board looks like. Dimensions are 53 x 37mm, so it's possible to install it into quite small spaces. The parts used are readily available, and many substitutions are available for both the MOSFET and power diode (the latter is only needed for motor speed control). The opamps should not be substituted, because the ones used were chosen for low power and their ability to swing the output to the negative supply rail.

Note that if used as a motor speed controller, there is no feedback, so motor speed will change with load. For many applications where DC motors are used, constant speed regardless of load is not needed or desirable, but it is up to you to decide if this will suit your needs.

Description

First, a description of PWM is warranted. As the pot is rotated clockwise, the input voltage changes linearly with rotation. At first, the voltage is such that the comparator output is just narrow spikes, which turn the MOSFET on for a very short period. Average current is low, so connected LEDs will be quite dim, or a motor will run (relatively) slowly. As the input voltage coming from the pot increases, the MOSFET is on for longer and longer, so increasing power to the load.

Figure 1 - PWM Waveform Generation

Figure 1 shows how the PWM principle works. The red trace is the triangle wave reference voltage, and the green trace is the voltage from the pot. When the input voltage is greater than the reference voltage, the MOSFET turns on, and current flows in the load. Because the frequency is relatively high (about 600Hz), we don't see any flicker from the LEDs, but the tone is audible from a motor that's PWM controlled. The PWM signal is shown in blue. The average current through the load is determined by the ratio of on-time to off-time, and when both are equal, the average current is exactly half of that which would be drawn with DC.

Figure 2 - Dimmer/Speed Controller Schematic

The circuit is shown in Figure 2. U1 is the oscillator, and generates a triangular waveform. R4 and R5 simply set a half voltage reference, so the opamps can function around a 6V centre voltage. U2A is an amplifier, and its output is a 10V peak to peak triangle wave that is used by the comparator based on U2B. This circuit compares the voltage from the pot with the triangle wave. If the input voltage is at zero, the comparator's output remains low, and the MOSFET is off. This is the zero setting.

In reality, the reference triangle waveform is from a minimum of about 1.5V to a maximum of 9.5V, so there is a small section at each end of the pot's rotation where nothing happens. This is normal and practical, since we want a well defined off and maximum setting. Because of this range, for lighting applications, an industry standard 0-10V DC control signal can be used to set the light level. C-BUS (as well as many other home automation systems) can provide 0-10V modules that can control the dimmer.

While a 1N4004 diode is shown for D2, this is only suitable if the unit is used as a dimmer. For motor speed control, a high-current fast recovery diode is needed, such as a HFA15TB60PBF ultra-fast HEXFRED diode. There are many possibilities for the diode, so you can use whatever is readily available that has suitable ratings. The diode should be rated for at least half the full load current of the motor, and the HFA15TB60PBF suggested is good for 15A continuous, so is fine with motors drawing up to 30A.

Construction

While it's certainly possible to build the dimmer on veroboard or similar, it's rather fiddly to make and mistakes are easily made. Also, be aware that because of the current the circuit can handle, you will need to use thick wires to reinforce some of the thin tracks. This is even necessary for the PCB version. Naturally, I recommend the PCB, and this is available from ESP. The board is small - 53 x 37mm, and it carries everything, including the screw terminals. The PCB is double-sided with plated-through holes, and has solder masks on both sides.

The MOSFET will need a heatsink unless you are using the dimmer for light loads only. It is necessary to insulate the MOSFET from the heatsink in most cases, since the case of the transistor is the drain (PWM output). For use at high current and possible high temperatures, the heatsink may need to be larger than expected. Although the MOSFET should normally only dissipate about 2W or so at 10A, it will dissipate a lot more if it's allowed to get hot. Switching MOSFETs will cheerfully go into thermal runaway and self destruct if they have inadequate heatsinking. You may also use an IGBT (insulated gate bipolar transistor) - most should have the same pinouts, and they do not suffer from the same thermal runaway problem as MOSFETs.

As noted above, there are many different MOSFETs (or IGBTs) and fast diodes that are usable. The IRF540 MOSFET is a good choice, and being rated 27A it has a generous safety margin. There are many others that are equally suitable - in fact any switching MOSFET rated at 10A or more, and with a maximum voltage of more than 20V is quite ok.

Testing

Connect to a suitable 12V power supply. When powering up for the first time, use a 100 ohm "safety" resisor in series with the positive supply to limit the current if you have made a mistake in the wiring. The total current drain is about 2.5mA with the pot fully off, rising to 12.5mA when fully on. Most of this current is in the LED, which is also fed from the PWM supply so you can see that everything is working without having to connect a load.

Make sure that the pot is fully anti-clockwise (minimum), and apply power. You should measure no more than 0.25V across the safety resistor, rising to 1.25V with the pot at maximum. If satisfactory, remove the safety resistor and install a load. High intensity LED strip lights can draw up to ~1.5A each, and this dimmer should be able to drive up to 10 of them, depending on the capabilities of the power supply and the size of the heatsink for the MOSFET.

1W LED Driver Circuit

2012-12-26T23:48:00.001-08:00

This circuit is designed to drive the 1W LEDs that are now commonly available. Their non-linear voltage to current relationship and variation in forward voltage with temperature necessitates the use of a 350mA, constant-current power source as provided by this supply. In many respects, the circuit operates like a conventional step-down (buck) switching regulator. Transistor Q1 is the switching element, while inductor L1, diode D1 and the 100mF capacitor at the output form the energy transfer and storage elements. The pass transistor (Q1) is switch-ed by Q2, which together with the components in its base circuit, forms a simple oscillator. A 1nF capacitor provides the positive feedback necessary for oscillation. The output current is sensed by transistor Q3 and the two paralleled resistors in its base-emitter circuit.

When the current reaches about 350mA, the voltage drop across the resistors exceeds the base-emitter forward voltage of transistor Q3 (about 0.6V), switching it on. Q3’s collector then pulls Q2’s base towards ground, switching it off, which in turn switches off the main pass transistor (Q1). The time constant of the 15kW resistor and 4.7nF capacitor connected to Q2’s base adds hysteresis to the loop, thus ensuring regulation of the set output current. The inductor was made from a small toroid salvaged from an old computer power supply and rewound with 75 turns of 0.25mm enamelled copper wire, giving an inductance of about 620mH. The output current level should be trimmed before connecting your 1W LED. To do this, wire a 10W 5W resistor across the output as a load and adjust the value of one or both of the resistors in the base-emitter circuit of Q3 to get 3.5V (maximum) across the load resistor.

Light Dimmer | Automatic Light Dimmer Circuit

2012-12-26T23:36:00.001-08:00

In many cases, the dimmer presented here may be built into a wall-mounted box containing the light switch. It is intended for use with 240 V incandescent lamps only. When it is fitted, and the light is switched on, the lamp does not come on fully for about 400 ms (which is not noticeable). When the light is switched off, it stays on unchanged for about 20 s, and then goes out gradually. This has the advantage that it is not immediately dark when the light is switched off. When light switch S1 is turned on, capacitor C2 is charged via R1, C1 and bridge rectifier D1–D4. Zener diode D5 limits the potential across C2 to about 15 V. After a short while, diode D6 lights, whereupon a potential difference ensues across light sensitive resistor R3, which is sufficient to trigger triac Tr1.

The light then comes on. When the light switch is turned off, C2 is discharged via P1, R2 and D6. When the potential across C2 drops, the brightness of the LED diminishes, so that the p.d. across R3 also drops. The increasing resistance of R3 effects phase angle control of the triac so that the light is dimmed gradually. The dimming time may be altered with P1 within the time range determined by network R2-C2. The circuit operates correctly only, of course, when the LDR is not exposed to light other than that from the LED. The type of LDR is not particularly important, as long as it is not too long: in the prototype, a model with a length of 5 mm was used.

1200 Watt Dimmer | 1200 Watt AC Dimmer by Triac Q4006LT

2012-12-23T04:37:00.001-08:00

This is Power AC Dimmer 1200 watt size. It is use a Triac Q4006LT. Friends ever tour is the foreign land has and to ever reach rest a hotel. On bed head has will head bed fire decorates. It has a button opens-close and a button controls the brightness with the equipment this/these be AC Dimmer follow our circuit can fine to decorate.

The VR1 for control the light besides when friends apply TRUE work. The Q1 -Q4006LT , should hold heat sink with and should be careful specially prohibit catch one ( part ) which part in the circuit , because read will bump against the electricity can suck. I hopes this circuit , friends can induce apply be AC Dimmer with electric other appliances bump against emphasize kind coil heat equipment , be lucky please yes.

Drill Controller | Mini-Drill Controller Circuit

2012-12-22T11:17:00.002-08:00

This circuit is intended as a revolution control for small dc motors as fitted, for instance, in small electric drills (such as used for precision engineering and for drilling boards, among others). The behavior of these motors, which are normally permanent magnet types, is comparable to that of independently powered motors. In theory, the rpm of these motors depends solely on the applied voltage.

The motor adjusts its rpm until the counter emf generated in its coils is equal to the applied voltage. There is, unfortunately, a drop across the internal resistance of the motor, which causes the rpm to drop in relation to the load. In other words, the larger the load, the larger the drop across the internal resistance and the lower the rpm. * This circuit provides a kind of compensation for the internal resistance of the motor: when the current drawn by the motor rises, the supply voltage is increased automatically to counter the fall in rpm. The circuit is based on an enhanced voltage regulator that consists of IC1 and Tl, which provides a reasonably large output current (even small drills draw 2-to-5 A). The "onset" supply voltage, and thus the rpm, is set by P2. Because of emitter resistance Rl, the currents through IC1 and Tl will be related to one another in the ratio that is determined by Rl and R2. Owing to this arrangement, the internal short-circuit protection of IC1 will also, indirectly, provide some protection to Tl. 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 (more or less) with R6. This arrangement automatically raises the output voltage to counter a threatened drop in rpm. The moment at which this action occurs is set by PI, so this circuit can be adapted pretty precisely to the motor used. If only very small motors are likely to be used, the power supply (transformer and bridge rectifier) can be rated more conservatively. As a guide, the current in the transformer secondary should be about 1.5 times the maximum dc output current.

Dimmer Circuit | lamp dimmer Circuit with LM555 and TIP2955

2012-12-18T09:45:00.004-08:00

This circuit is DC Dimmer Circuit. By use IC LM555 be model Astable Multi vibrator. It is can change translate Duty Cycle with fining VR1 and VR2 be formed fine brightness level that want.

The output of IC1 be formed limit load in something Oscillator and limit current of Q2 with. The D1 be formed protect Oscillate. For the Q1- TIP2955 and Q2 – MJ2955 should hold heat sink unless. Still can use S1 choose wasp a light bulb directly or Dimmer Lamp. For load of this circuit you can use 10A 12V topmost. Request a friend is entertained with Spot lamp dimmer by LM555 and TIP2955.

Undestanding Pulse Width Modulation (PWM) | PWM Fan controller Circuit

2012-12-14T10:27:00.003-08:00

PWM or Pulse Width Modulation has generally been regarded as too complicated for PC fan speed control compared against using rheostats or linear voltage regulators such as the LM317. I present here a PWM circuit that is simple and cheap enough to be built by the casual electronics builder.

Why would you want to use PWM instead of a rheostat or voltage regulator? Well, like most things, each method has it's own strengths and disadvantages:

Rheostats
Pros: Cheap and easy to use.

Cons: Difficult to find suitable rheostats, introduces current limiting causing the fan to fail to start or stall at slow speed settings.

Linear voltage regulators
Pros: Does not have rheostat like current limiting, temperature control can be incorporated.

Cons: Regulator can generate considerable heat which limits the maximum fan power. (The more powerful the fan, the more heat is generated), maximum output voltage to the fan can be several volts less than the supply limiting the maximum cooling from the fan. (A by-pass switch can be fitted to eliminate this problem, but this adds to the complexity of the circuit).

PWM

Pros: As linear voltage regulator, plus comparatively little heat is generated by the circuit allowing higher powered fans to be used, output is virtually 0-100%, eliminating the need for a bypass switch, fans do not stall or fail to start at minimum fan speed.

Cons: The fan speed sensing is disabled, can cause "growling" noises at very low speed settings with some fans.

What is PWM?

In simple terms, PWM involves rapidly switching the supply to the fan on and off, in this case 30 times a second, (30Hz). By altering the relative on to off times the average voltage "seen" by the fan is also altered. E.G. Assuming a 12V supply, when the on/off ratio = 50%/50% the fan will "see" 6V, likewise when the on/off ratio is 75%/25% the fan "sees" 9V. Obviously 100% output is achieved by having the output on continuously and at 0% the output is off. It is this on/off switching that makes the fan speed sensor inoperative.
The circuit uses a purpose made chip, MIC502 made by MICREL. Fan speed is adjusted by varying VR1. With the component values shown the output is 40%-100%. ( 4.8 - 12V). So far every fan I have tested runs at 4.8V. To guarantee the fan starts when the computer is switched on, the chip automatically runs the fan at full output for approximately 2 seconds before dropping to the preset speed. Changing the value of R1 and R2 to 7K5 ohms will give an output range of 0% - 100%.
If desired, R1 and R2 can be replaced with 22K variable preset resistors to allow exact tailoring of the control range. Varying R1 will alter the maximum output, whilst R2 controls the minimum. Note these adjustments are interactive with each other and will require some trial and error to achieve the desired range. The diode, D1 is to protect the transistor from reverse voltage spikes when switching the fan off. Using modern DC axial fans should not be a problem and D1 may be considered optional. Since I cannot test every possible device people may connect to the circuit I have included D1 for completeness.
On the other hand, the decoupling capacitor, C2 is NOT optional. During testing it became apparent that the chip does not like "noisy" supplies. E.G. My 350W " Enermax has very long leads and poor quality connectors. This does not help maintain a clean supply. Things may be different for you but I consider C2 to be necessary. C1 sets the pulse frequency, in this case 30Hz.
During testing "growl" noise at low speeds was not a problem. If "growl" is a problem with your specific fan then changing the value of C1 should help. Use the formula C = 3/f where C is in microfarad (uF) and f is the desired frequency in hertz (Hz). Try frequencies in the range 30-100 Hz. R4 limits the base current to the transistor T1. T1 is rated at 5A which equates to 60W of fan!! In practise the circuit should be capable of running any reasonable number of case fans. With several powerful fans connected the transistor may get warm so a small heatsink may be required.
Several channels can be made to make a multi channel fan bus. Only one "C2" is required if all the channels are built on the same board. Looking at the circuit diagram, the "+12V" and "0V" terminals connect to the respective connections on the PSU Molex connector. The "FAN+" and "FAN-" connect to the corresponding +v and -v terminals on the fan.

Component List :

IC1 = MIC502BN (82-4026)
T1 = TIP122 (81-0172)
D1 = 1N4001 (47-3420)
R1 = 10K (62-2146)
R2 = 15K (62-2154)
R4 = 270R (62-2070)
VR1 = 10K Linear (65-0715)
VR2 = 47K Linear (65-0725)
Thermistor = (61-0515)
C1 = 0.1uF (10-3220)
C2 = 220uF 25V (11-0265)

Adding Temperature control.

Here the resistor R1 has been replaced with a thermistor to give temperature control. The fan speed is set by VR1 and as the temperature rises, so the fan speed will increase to compensate.

This version is identical to the temperature control above, except for the addition of a "sleep" setting. The idea is to turn the fan off when the temperature falls below the value set by VR2.

Overload Protection | Overload Protection Circuit With with Reset Option

2012-12-12T09:26:00.000-08:00

The circuit presented here can be used as overload protector with reset option for inverters or as an electronic fuse in AC mains supply. In this overload protection circuit, the mains supply to the load s like refrigerator is routed via the the N/C (normally closed) contacts of relay RL1. In an inverter, the relay contacts could be used as ‘inverter oscillator’ on/off control. Whenever overload occurs, it inhibits inverter oscillator circuit, which, in turn, stops generation of power. In applications like inverters and UPS, the load must not exceed the rated output power since it can cause excess heating of output transformer windings and active driving devices and thereby damage them.

Resistor R1 is used as the overload sensing element. When the load exceeds the maximum rated value, it draws current in excess of its rated value. This causes the potential drop across resistor R1 to increase. An optocoupler is used to sense this voltage drop. The optocoupler, in addition, isolates the AC mains part from the rest of the circuit physically. Resistor R1 is selected as 1 ohm for 230V, 500 watts (max.) load capacity. When the load just exceeds 500 watts, the current through R1 is approximately 2.1 amperes, producing a potential difference of 2.1 volts across R1. The inbuilt transistor inside the optocoupler senses this voltage and its collector current increases proportionally. When the current reaches the required designed value, voltage drop across resistor-preset combination R3-VR1 also increases. (Note. The power dissipated in 1-ohm resistor for 500W load is just 2.1 watts, which is negligible compared to the maximum power rating of the load. To use this circuit for 1kW load, select R1 as 0.5-ohm, 10W.) Overload limiting point can be set by preset VR1. When the potential at wiper of preset VR1 becomes greater than VZ+VBE (where VZ is the breakdown voltage of zener diode ZD1 and VBE the for ward voltage drop at the base-emitter junction of transistor T1), it causes forward biasing of transistor T1. This results in the collector of transistor T1 to be pulled down to ground and trigger IC555, which is connected in bistable mode. The output of IC1 causes overload indicating LED1 to glow and forward biases transistor T2 to energise relay RL1. Once the output of bistable IC1 goes high, it continues to remain high, unless reset push button S1, which is connected be tween Vcc and threshold terminal (pin 6) of timer 555, is pressed. On pressing S1, a high pulse is applied to the threshold pin that resets the flip-flop output to low state. The circuit can be reset after removing unwanted loads.

RMS Voltage Control Circuit with Opto Triac MOC3021 and BT136

2012-12-11T09:38:00.002-08:00

Triac is a power electronic component that conducts in both directions when triggered through gate. Figure below shows a generic working of triac.As it can be seen that at time t1, angle of sinusoid is 45' which means that if we triggered triac at this angle i-e at 45', only shaded blue area will pass through the triac and hence through the load. Observe that shaded blue are has RMS Voltage less than the pure sinusoid. This is the basic principle by which RMS Voltage control is accomplished. Firing needs a small pulse at gate that can be give through microcontroller also. Similarly at firing angle 90' (firing angle is an angle with reference zero crossing at which the triac is triggered using gate pulse) , only red part of sinusoid will pass through the triac giving us the RMS 110V for 220V.

MOC3021 is an optotriac (product of Motorola) that is used for isolation between power and driving circuitry. Note that when C828 on the base is applied voltage>0.7V, optotriac gets triggered. As the triac gets triggered now, the positive or negative voltage (whatever maybe) get pass through the gate of BT136 (triac) and hence triggered it. It should be noted here that by using above arrangement we can control the RMS voltage in both directions. What needs to be taken care of, is the triggering time or firing angle.

There is a need of a zero-crossing detector that will give us the reference for providing delay for desired firing angle. In above example, for firing angle to be 90' for 220V 50Hz AC signal, we need to have a delay of 2.5 ms (t1=2.5ms) right after each zero crossing. Usually MOC3021 is driven through microcontroller, which gives the firing pulse on the basis of interrupt generated by the zero-crossing detector.

The above circuit is mainly used as a dimmer and is often used speed controlling of AC motor. There are other versions of the above circuits available that caters for the inductive load which will be discussed later.

DC Regulator Circuit | 12V -10A Regulator with IC 723+2N3055

2012-12-11T09:26:00.001-08:00

This is circuit regulator 12V 10A by IC 723+2N3055.Q 2N3055 x 2 for to increase form IC LM723.To use transformer 10A, Transistor to Hold Heat-sink.To adjust the output voltage simplyt by VR1 – 1K.

Regulator circuit 12V 10A by IC 723+2N3055

A friend of me wants 12V Power supply for High Current 10A load. Me tries to search see meet this circuit will should is appropriate. Because of use IC LM723. Be the integrated circuit Voltage Regulator at good one although older already. But still be usable well. Fine decorate voltage output with well. Besides still have the transistor 2N3055 numbers are highly popular transistor again the one number. Make the all equipment of this circuit seeks easy certainly. If friends want to give 10A electric tall currents. Should use a pot transforms the sky that has 10A sizes with. For VR1 give for fine decorate voltage output get as well be can fine about 0-16V. The detail is other , please see in the circuit better.

Automotive Speed Indicator | Speed Indicator Circuit for Auto Mobiles

2012-12-10T10:32:00.001-08:00

The speed of an automobile can be indicated by detecting the pulses generated by the ignition system and causing an LED to light. The circuit utilizes a quad NOR gate IC chip. Two of the gates are configured as a one shot multivibrator which produces a fixed duration pulse each time the primary circuit of the automobile ignition system opens the circuit to the ignition coil.

The other 2 gates are used as buffers which provide an accurate rectangle pulse. As the number of pulses per second increases, the voltage fed to the base of of the NPN transistor becomes high enough to cause it to conduct and turn on the LED. The speed at which the LED lights is set by R4. The input of the circuit is connected to the distributor side of the ignition coil or to the tachometer connection on those cars that are equipped with electronic ignition.

Mains LED | Mains operated LED lamp Circuit

2012-12-09T07:54:00.002-08:00

This is a very simple and cost effective mains operated LED lamp which gives a very bright white light.Since no transformer is used, the circuit is very compact and light weight.The mains supply is given to the bridge rectifier via the parallel network formed between R1 and C1.

The bridge rectifies the mains supply.The resistor R2 limits the current through the LEDs.The capacitor C2 acts as a filter.

Note:
The circuit can be assembled on a general purpose PCB.
The bridge D1 can be made by using four 1N 4007 diodes.
D2 to D13 can be bright white LEDs.

Ac Stabilizer Circuit | Triac Controlled Automatic Voltage Stabilizer

2012-10-14T01:05:00.000-07:00

This triac control AC voltage stabilizer circuit has been design, the voltage switching transitions are very smooth with minimum wear and tear, resulting in efficient voltage stabilization. Discover the whole construction procedure of this unique, solid state mains voltage stabilizer.
The proposed circuit of a triac controlled AC voltage stabilizer will provide an excellent 4 step voltage stabilization to any appliance at its output. With no moving parts involved its efficiency is further enhanced. Find out more of this silent operator: power guard.The circuit of an automatic voltage stabilizer discussed in one of my previous articles, though useful, due to its simpler design, does not have the capability of controlling the different levels of varying mains voltages discretely. The proposed idea though not tested, looks pretty convincing, and if the critical components are properly dimensioned, should work as expected.
The present circuit of triac controlled AC voltage stabilizer is outstanding in its performance and is almost an ideal voltage stabilizer in every respect. As usual the circuit has been exclusively designed by me. It is able to control and dimension the input AC mains voltage accurately through 4 independent steps. The use of triacs make it sure that the changeovers are quick (within 2 mS) and with no sparks or transients usually associated with relay type of stabilizers. Also since no moving parts are employed, the entire unit becomes completely solid state and almost permanent.

CAUTION: EACH AND EVERY POINT OF THE CIRCUIT PRESENTED HERE MAY BE AT AC MAINS POTENTIAL, THEREFORE EXTREMELY DANGEROUS TO TOUCH IN SWITCHED ON POSITION. UTMOST CARE AND CAUTION IS ADVISED, USE OF A WOODEN PLANCK UNDER YOUR FEET IS RECOMMENDED. NEWBIES PLEASE KEEP AWAY.

The functioning of the circuit may be understood through the following points:
Transistors T1 to T4 are all arranged to sense the gradual rise in the input voltage and conduct one after the other in sequence as the voltage rises and vice versa.
Gates N1 to N4 from IC 4093 are configured as buffers. The outputs from the transistors are fed to the inputs of these gates.
All the gates are interconnected to each other in such a way that the output of only a particular gate remains active at a given period of time according to the level of the input voltage.
Thus, as the input voltage rises the gates respond to the transistors and their outputs subsequently become logic hi one after the other making sure that the previous gate’s output is shut OFF and vice versa.
The logic hi from the particular buffer is applied to the gate of the respective SCR which conducts and connects the relevant “hot” line from the transformer to the external connected appliance.
As the voltage rises, the relevant triacs subsequently select the appropriate “hot” ends of the transformer to increase or decrease the voltage and maintain a relatively stabilized output.

Construction and Testing Tips

The construction of this triac control AC power guard circuit is simple and just a matter of procuring the required parts and assembling them correctly over a general PCB. It is pretty obvious that the person who is attempting to make this circuit knows a bit more than just the basics of electronics. Things may go drastically wrong if there is any error in the final assembly.
You will require an external variable (0 to 12 volts) universal DC power supply for setting up the unit in the following way:
Assuming that an output supply of 12 volts from TR1 corresponds to 225 volts input supply, through calculations we find that it will produce 9 volts at an input of 170 volts, 13 volts will correspond to 245 volts and 14 volts will be equivalent to an input of approximately 260 volts.
Initially keep the points “AB” disconnected and make sure the circuit is totally disconnected from the AC mains.
Adjust the external universal power supply to 12 volts and connect its positive to the point “B” and negative to the common ground of the circuit.
Now adjust P2 until LD2 is just switched ON. Reduce the voltage to 9 and adjust P1 to switch ON LD1.
Similarly, adjust P3 and P4 to illuminate the relevant LEDs at voltages 13 and 14 respectively.
The setting procedure is now complete. Remove the external supply and join points “AB” together.
The whole unit may now be connected to the mains AC so that it can start working right away.
You may verify the performance of the system by supplying a varying input AC through an auto transformer and checking the output using a digital multimeter.
This triac controlled AC voltage stabilizer will shut OFF at voltages below 170 and above 300 volts.

Parts List

You will require the following parts for the construction of this SCR control ac voltage stabilizer:
All resistors are Â¼ Watt, CFR 5%, unless otherwise stated.
R5, R6, R7, R8 = 1M Â¼ watt,
All Triacs are 400 volts, 1KV rated,
T1, T2, T3, T4 = BC 547,
All zener diodes are = 3 volts 400 mW,
All Diodes are = 1N4007,
All presets = 10K linear,
R1, 2, 3, 4, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 = 1K Â¼ watt,
N1 to N4 = IC 4093,
C1 and C3 = 100Uf/ 25 volts,
C2 = 104, ceramic,
Power Guard Stabilizer Transformer = “Made to order” having 170, 225, 240, 260 volts output Taps at 225 volts input supply, or 85, 115, 120, 130 volts taps at 110 AC input supply.
TR1 = Step down transformer, 0 – 12 volts, 100 mA.

Mains High and Low Voltage Protector Circuit, Using IC LM 324

2012-10-11T10:32:00.001-07:00

The inclusion of op amps makes the circuit operations much accurate and tripping points adjustable to any levels as desired by the user.
As shown in the figure, we can see two OP amps from the IC LM 324 are used for the required detection.

Refer circuit diagram

The upper op amp has its non inverting input rigged to a preset and is terminated to the supply DC voltage, pin #2 here is provided with a reference level, so that as soon as the potential at pin #3 goes above the set threshold (by P1), the output of the op amp goes high.

Quite similarly the lower op amp is also configured for some voltage threshold detection, however here the pins are just reversed, making the op amp output go high with low voltage input detection.

Therefore, the upper op amp responds to high voltage threshold and lower op amp to low voltage threshold.
For both the detections, the output of the respective op amp becomes high.

Diodes D5 and D7 make sure that their junction produces a common output from the op amp output pin outs. Thus whenever any one of the op amp output goes high, it is produced at the junction of D5, D7 cathodes.

Transistor T1’s base is connected to the above diode junction, and as long as the op amps output remain low, T1 is allowed to conduct by getting the biasing voltage through R3.

However the moment any of the OP amp output goes high (which may happen during abnormal voltage conditions) the diode junction also becomes high, restricting T1 from conducting. Relay R1 instantly switches OFF itself and the connected load.

Thus the connected load remains ON as long as the op amp outputs are low, which in turn can only happen when the input mains is within the safe window level, as adjusted by P1 and P2. P1 is set for detecting high voltage levels while P2 for the lower unsafe voltage level.

Pin Details of IC LM 324

Parts List

R1, R2, R3 = 2K2,

P1and P2 = 10K preset,

C1 = 220uF/25V

All diodes are = 1N4007,

T1 = BC557,

Relay = 12 V, 400Ohms, SPDT,

op amps = 2 opamps from IC LM 324

Zeners = 4.7 volts, 400mW,

Transformer = 12V, 500mA

Fan Regulator Circuit | Remote-Controlled Fan Regulator Circuit Diagram

2012-09-30T08:05:00.000-07:00

Using this circuit, you can change the speed of the fan from your couch or bed. Infrared receiver module TSOP1738 is used to receive the infrared signal transmitted by remote control. The circuit is powered by regulated 9V. The AC mains is stepped down by transformer X1 to deliver a secondary output of 12V-0-12V. The transformer output is rectified by full-wave rectifier comprising diodes D1 and D2, filtered by capacitor C9 and regulated by 7809 regulator to provide 9V regulated output. Any button on the remote can be used for controlling the speed of the fan. Pulses from the IR receiver module are applied as a trigger signal to timer NE555 (IC1) via LED1 and resistor R4.

IC1 is wired as a monostable multivibrator to delay the clock given to decade counter-cum-driver IC CD4017 (IC2).Out of the ten outputs of decade counter IC2 (Q0 through Q9), only five (Q0 through Q4) are used to control the fan. Q5 output is not used, while Q6 output is used to reset the counter. Another NE555 timer (IC3) is also wired as a monostable multivibrator. Combination of one of the resistors R5 through R9 and capacitor C5 controls the pulse width. The output from IC CD4017 (IC2) is applied to resistors R5 through R9. If Q0 is high capacitor C5 is charged through resistor R5, if Q1 is high capacitor C5 is charged through resistor R6, and so on.
Optocoupler MCT2E (IC5) is wired as a zero-crossing detector that supplies trigger pulses to monostable multivibrator IC3 during zero crossing. Opto-isolator MOC3021 (IC4) drives triac BT136. Resistor R13 (47-ohm) and capacitor C7 (0.01µF) combination is used as snubber network for triac1 (BT136). As the width of the pulse decreases, firing angle of the triac increases and speed of the fan also increases. Thus the speed of the fan increases when we press any button on the remote control. Assemble the circuit on a general-purpose PCB and house it in a small case such that the infrared sensor can easily receive the signal from the remote transmitter.

Security Lock | Door Security Electronic Key Combination Lock

2012-09-22T08:48:00.000-07:00

This is a relatively simple circuit of electronic lock of safety with code of 7 digits. It should is given attention in the time that will be stepped the keys, that shape code and it does not exist it delays. With the right step of keys and if code is right then is activated exit Q7 for roughly 4 seconds, driving the transistor Q2, which with the line can drive one relay, for the opening of door, or any other circuit.

With LED D we can have optical clue of activation. The code of circuit, as it has been given have been:1704570 but can change, if we change the connections between in the exits of IC1 and the switches.

Parts List :
   R1-7=4.7Kohm
    R8=15Kohm
    R9=1Mohm
    R10-13=10Kohm
    R11=100ohm
    R12=220Kohm
    R14=1.2Kohm
    C1-3=100nF 100V
    C2=4.7uF 25V
    D1-2=1N4148
    D3=RED LED 3mm
    IC1=4022
    Q1=BS170
    Q2=BD679
    S1-10=Push button or keyboard

Triac based DC Motor Speed Controller Circuit

2012-09-22T08:33:00.001-07:00

This Triac-based dc motor speed controller circuit is designed for controlling the speed of small household motors like drill machines. The speed of the motor can be controlled by changing the setting of P1. The setting of P1 determines the phase of the trigger pulse that fires the Triac. The circuit incorporates a self-stabilizing technique that maintains the speed of the motor even when it is loaded.

For example, when the motor of the drill machine is slowed down by the resistance of the drilled object, the counter-EMF of the motor also decreases. This results to a voltage increase in R2-P1 and C3 causing the Triac to be triggered earlier and the speed increases accordingly.