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15 seconds delayed switch-off A good idea for bedroom lamps This circuit is intended to let the user turn off a lamp by means of a switch placed far from bed, allowing him enough time to lie down before the lamp really switches off. Obviously, users will be able to find different applications for this circuit in order to suit their needs. Circuit diagram : Courtesy Light Circuit diagram Due to the low current drawing, the circuit can be supplied from 220Vac mains without a transformer. Supply voltage is reduced to 10Vdc by means of C1 reactance, a two diode rectifier cell D1 & D2 and Zener diode D3. IC1 is a CMos 555 timer wired as a monostable, providing 15 seconds on-time set by R3 & C4. When SW1 is closed, IC1 output (pin 3) is permanently on, driving Triac D4 which in turn feeds the lamp. Opening SW1 operates the monostable and, after 15 seconds, pin 3 of IC1 goes low switching off the lamp. Notes: The circuit is wired permanently to the mains supply but current d...

There are many approaches to the problem of activating a light when it becomes dark, and a recent Design Idea covers this topic (Reference 1). Some approaches require a dc power supply and an electromechanical relay, but a better approach involves feeding the device directly from the ac line, minimizing the number of components  ( Figure 1 ). Figure 1. The photoresistor activates the TRIAC and the load when darkness falls. The heart of the device is a light-sensitive cadmium-sulphide resistor, PR, with a resistance of approximately 200 kΩ in the dark and decreasing to a few kilohms in the light. PR and capacitor C1 form an ac-voltage divider. In daylight, the voltage across PR is too low to generate the required gate-trigger current to turn on bidirectional ac switch Q1, thus keeping the load – usually a lamp – off. When it becomes dark, PR’s resistance rises, resulting in an increase in the TRIAC’s gate current that triggers the TRIAC and lights the lamp. The circuit uses inexpens...

The circuit of the running light comprises two integrated circuits (ICs), a resistor, a capacitor and seven light-emitting diodes (LEDs), Decade scaler IC2 ensures that the LEDs light sequentially. The rate at which this happens is determined by the clock at pin 14. Circuit diagram : 6-Channel Running Light Circuit Diagram The clock is generated by IC1, which is arranged as an astable multivibrator. Its frequency is determined by R1-C1. The touch switch, consisting of two small metal disks is optional. When switch S1 is in position ‘off ’, the circuit may be actuated by the touch switch. By the way, this enables the circuit to be used as an electronic die (in which case the LEDs have to be numbered from 1 to 6). The running light is powered by a 9 V battery or mains adaptor. It draws a current not exceeding 20 mA.

The wiring process of fluorescent tube lamp/light with Ballast,Starter is quite easy and simple. In most cases when we buy a fluorescent light it comes in a complete set with all wire connected. If you want do it yourself , you can buy all the parts individually. And you can complete all connection of the fluorescent light/lamp with the help of this wiring circuit diagram. Main parts of Fluorescent Tube Light:      1.Fluorescent Tube      2.Ballast      3.Starter      4.Holder, wire etc. How Fluorescent Light's works: The starter is like a key of fluorescent light because it is used to light up the tube. When we connect the AC supply voltage to the circuit, then the starter act like short circuited and current flow through those filament (located at the first and second end of the tube light) and the filament generate heat and it ionized the gas ( mercury vapor ) in the fluorescent tube lamp. So the gas beco...

This circuit is of an 2x 2,500W RMS stereo amplifier, super-light and without switching-mode power supply. The circuit just shows a channel, and the power supply that it assists to the two channels. The audio circuit should be duplicated, but the power supply assists to the two channels without problems. A special care should be destined to the insulating transformer of the audio line, that should be of audio-high-quality, of the type used in microphone pre amps input line. The whole group (2 channels) of 5,000W RMS it should not weigh more than 32 lbs, already inside of an appropriate metallic box. Warning This circuit is exclusively for amateur use. It contains not-isolated parts of the electric AC net and it can be very dangerous. The connections for the speakers are not isolated of the domestic AC net and it requests extra care. This procedure seeks to substitute a conventional power supply with great weight and cost reduction, without necessarily to use a switching-mode power supp...

Measure AC mains voltage without using a multimeter. All you need to do is to slightly modify the light dimmer fitted at the base of a table lamp for use as a voltmeter . When the dimmer is turned anticlockwise to a point where the filament glow is just visible, that point can be used as the reference point for measuring the voltage. Light dimmer Circuit Diagram First, remove the old knob and fix a circular white paper around the shaft. Now put back a skirted knob with a cursor as close to the paper as possible and mark two extremities of the pot on the paper as CW and ACW (see Fig. 2). AC volts scale marking Switch on the lamp via a variac and feed 50 volts. Rotate the potmeter knob anticlockwise until the filament glow is just visible and mark that point against the cursor as 50V. Keep on increasing the voltage to 100, 150, 180, 200 and 220 using the variac and calibrating the scale for all the voltages. Now a voltage scale is created. The only snag is that the voltage is increasing ...

Today we'll answer the frequently asked question. "why LED strip light won't light up". If you find your flexible LED strip light won't light up or power up, you may check the following troubleshooting information for help. 1. The lamp beads of led strip light must be broken or damaged during transportation if the light is not covered with full protection. 2. There must be a faulty at the light's soldering points. The soldering may come off if there is any shock during transportation. 3. Soldering with poor quality may cause embrittlement or shedding when the strip light is bent for use. 4. Cheat on tin soldering materials can also cause the same problem as the 2 point we just mentioned. 5. LED lights with flexible installation bending angle is too large, resulting in LED lights with flexible joints and lead to bright copper separation flexible led strip lights 6. A excessive bending may result in the disconnection between the joints and copper foil. 7. Th...

A very simple light alarm schematic circuit project can be designed using some common electronic parts, as you can see in the circuit diagram bellow . This light alarm schematic circuit project will sound as soon as the drawer is opened and light falls on the Darlington phototransistor. The output alarm may be redesigned to activate a relay or triac. This simple light alarm schematic circuit project use a MAL12 LDR photoresistor as a sensor . Light Alarm Schematic Circuit diagram The 14011 quad , 2 input, NAND gate is wired up to oscillate when the input to it goes high, that is the BC557 transistor turns on after light is detected by the MAL12. The oscillating output from the 14011 turns the BC547 on and off , making the buzzer to sound. After the alarm has started and it is put back into dark conditions , alarm will continue to sound for about 3 - 5 seconds. This is due to the 1uF capacitor and 4M7 resistor which keep the input to the 14011 high . The circuit is very simple and must ...

Here the simple traffic light controller which is could be used to educate kids rudiments of traffic light guidelines. The circuit utilizes easily available electronic parts. It generally consists of rectifier diodes (1N4001), a 5V regulator 7805, two timers circuit using IC 555, two relays (5V, single-changeover), three 15W, 230V light bulbs and also several discrete parts. Traffic Light Controller Circuit Diagram: Mains electrical power is stepped down by transformer X1 to provide a secondary output voltage of 9V, 300 mA – AC. Then the transformer output current is rectified by a full-wave bridge rectifier composed of diodes D1 through D4, filtered by capacitor C1 and also regulated by IC 7805 (IC1). IC2 is wired as a multivibrator with ‘on’ and ‘off’ periods of about 30 seconds each with the part values determined. Once mains power switch is turned on, pin 3 of IC2 goes high for 30 seconds. This, in turn, energises relay RL1 via transistor T1 and the red bulb (B1) glows through its ...

T his  automatic  bicycle  light  makes cycling in the dark much  easier (although you still need  to pedal of course). The circuit  takes  the  ambient  light  level  into account and only turns on  the light when it becomes dark.  The light is turned off when no  cycling has taken place for over  a minute or if it becomes light  again. The biggest advantage of  this circuit is that it has no manual controls. This way you can  never ‘forget’ to turn the light  on or off. This makes it ideal for  children and those of a forgetful  disposition. Bicycle Light Image : To detect when the bicycle is  used (in other words, when the  wheels turn), the circuit uses a  reed switch (S1), mounted on  the frame close to the wheel.  A small magnet is fixed to the  spokes (similar to that used with  most  bicycle  speedometers),  which  ...

The LED bicycle light that we described in the July/August 2009 edition of Elektor has proved very  popular. The author was particularly struck by the basic design, but as always, there is room for a little improvement! Below we describe two enhanced variations on the original theme. Both circuits are, like the 2009 original, powered from a 6 V (rechargeable) battery, shown here as Vl. The simpler of the two circuits, which consists of four transistors, is in function essentially the same as the original version. lt takes the form of a boost converter with feedback provided by the voltage drop across a current sensing resistor, in this case R2. A value of 6.2 O for R2 is suitable for use with four white LEDs at D4 to D7, and gives an LED current of approximately 20 mA. The 250 mW Zener diode D10 is provided to limit the output voltage in the case that the LED chain should go open-circuit, pulling  the gate of the  MOSFET to ground via T3, T1 and T2 if the output voltage exceeds the br...

LIGHT ALARM - 1 This circuit operates when lightweight|the sunshine} Dependent Resistor receives light. When no lightweight falls on the LDR, its resistance is high and also the transistor driving the speaker isn't turned on. When lightweight falls on the LDR its resistance decreases and also the collector of the second transistor falls. This turns off the primary transistor slightly via the second 100n and also the initial 100n puts a further spike into the bottom of the second transistor. This continues till the second transistor is turned on as onerous because it will go. the primary 100n is currently nearly charged and it cannot keep the second transistor turned on. The second transistor starts to turn off and each transistors swap conditions to provide the second half of the cycle. LIGHT ALARM - 2 This circuit is comparable to lightweight Alarm -1 however produces a louder output as a result of the speaker being connected directly to the circuit. The circuit is essentially a h...

Description This is a simple circuit which is build around a CMOS Ic 4060 and LDR. During the day time LDR has low resistance which keeps the pin 12 of the IC1 high. And also for the night LDR resistance become high and the pin 12 or IC1 is becomes low and the IC start oscillating, which indicate by the flashing of LED D3.The values of the timing components R1, R2, C4 are so selected that the out put pin3 of IC1 goes high after 8 hours. That means the high output drives the triac to switch on the lamp around 2’O clock.At morning time the LDR resistance drops and the pin 12 of IC1 goes high and stop the oscillating which makes the lamp off. Where Switch S1 is used to manually ON the lamp.The capacitor C2 prevents false triggering. Circuit Diagram Notes. * Assemble the circuit on a good quality PCB or common board. * The LDR can be general purpose LDR. * The light sensitivity can be adjusted using the preset R6. *  The IC1 must be mounted on an  IC holder.

LDRs or lightweight Dependent Resistors are terribly helpful particularly in light/dark sensor circuits. Normally the resistance of an LDR is incredibly high, typically as high as a thousand 000 ohms, however once they are illuminated with lightweight resistance drops dramatically.  The animation opposite shows that when the torch is turned on, the resistance of the LDR falls, permitting current to have it.Circuit Wizard software has been used to show, the vary of values of a ORP12, LDR . When a light-weight level of a thousand lux (bright light) is directed towards it, the resistance is 400R (ohms). When a light-weight level of ten lux (very low light level) is directed towards it, the resistance has risen dramatically to ten.43M (10430000 ohms). This is an example of a light-weight sensor circuit : When the sunshine level is low the resistance of the LDR is high. This prevents current from flowing to the bottom of the transistors. Consequently the LED doesn't lightweight. However...

AUDIO FREQUENCY LIGHT MODULATOR ELECTRONIC DIAGRAM Light has function to replace cable from audio source to speaker. Transformer X2 is utilized to lock the audio signal. VR1 works as the amplitudo modulator from the T1 signal output. Parts list :     Resistor R1:  47k ohm     Resistor R2 : 22k ohm     Resistor R3 : 220 ohm     Diode D1-D7 : 1N4001     VR1 : 1k ohm     Polar capacitor C1 : 470 uF/25V     Polar capacitor C2 : 1 uF     Capacitor C3 : 0.1 uF     Transistor T1-T2 : BC148     Transformer X1 : 220 V AC/0-12V AC     X2 : AF output     Transistor SCR1-SCR2 : BA654

This is the Simple Battery operated emergency light Circuit Diagram. This simple circuit providers battery operated emergency lighting instantaneously upon failure of the regular ac service. When line power is restored, the emergency light turns off and the battery recharges automatically. Battery operated emergency light Circuit Diagram     The circuit is ideal for use in elevator cars, corridors and similar places where loss of light due to power failure would be undesirable. Completely static in operation, the circuit requires no maintenance. With ac power on, capacitor CI charges through rectifier CRI and resistor Rl to develop a negative voltage at the gate of the C106Y SCR . By this means, the SCR is prevented from being triggered, and the emergency light stays off. At the same time, the battery is kept fully charged by rectifier CR2 and resistor R2. Should the ac power fail, CI discharges and the SCR is triggered on by battery power through resistor R3. The SCR t...

Flashing 13 LED unit, 3V supply, Also suitable for jogger/walkers This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency flashing LEDs arranged in a pseudo-rotating order. Due to low voltage, low drain battery operation and small size, the device is suitable for mounting on bicycles as a back light, or to put on by jogger/walkers. IC1 is a CMos version of the 555 IC wired as an astable multivibrator generating a 50% duty-cycle square wave at about 4Hz frequency. At 3V supply, 555 output (pin 3) sinking current operation is far better than sourcing, then LEDs D1-D6 are connected to the positive supply rail. In order to obtain an alternate flashing operation, a second 555 IC is provided, acting as a trigger plus inverter and driving LEDs D7-D12. D13 is permanently on. The LEDs are arranged in a two series display as shown below, with a center LED permanently on. This arrangement and the alternate flashing of the two series of LEDs provide a pseudo...

Description    On my mountain bike I always used to have one of those well-known flashing LED lights from the high street shop. These often gave me trouble with flat batteries and lights that fell off. As an electronics student I thought: “this can be done better”. First I bought another front wheel, one which has a dynamo already built in the hub. This supplied a nice sine wave of 30 Vpp (at no load). With this knowledge I designed a simple power supply. The transistors that are used are type BD911. These are a bit of an over-kill, but there were plenty of these at my school, so that is why I used them. Something a little smaller will also work. The power supply is connected to an astable multi-vibrator. This alternately drives the front light and the rear light. The frequency is determined by the RC time-constant of R3 and C3, and R2 and C4. This time can be calculated with the formula: t = R3×C3 = 20×103×10×10-6 = 0.2 s You can use a 22k (common value) for R2 and R3, that d...