Click para ampliarThree Way Touch Lamp
A three-way switch to control a lamp (off-dim-bright, etc.) uses an NE555 timer to generate a one-second pulse, triggered by ambient ac fields that are picked up by the human body. C1 and D1 form an input network. U2 is a decode counter/divider and drives one of 10 outputs (three are used). The logic outputs drive various resistors in series with the LED in the optocoupler. The optocoupler controls a triac that is in series with a load (lamp, etc.).
By reconfiguring the outputs of U2, more than three brightness levels can be obtained, up to 10. An 1N914 and resistor will be required for each output.
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By reconfiguring the outputs of U2, more than three brightness levels can be obtained, up to 10. An 1N914 and resistor will be required for each output.
Click para ampliarThree Power Level Triac Controller
Three power levels are supplied by the two logic inputs of this enhanced circuit. R5, D4, D5, and
C2 form a power supply for the logic IC. They can be omitted if another source of low voltage is available.
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C2 form a power supply for the logic IC. They can be omitted if another source of low voltage is available.
Click para ampliarSensitive Triac Controller
The single transistor connected between the capacitor and the common side of the ac line allows a logic-level signal to control this triac power circuit. Resistor R2 prevents false triggering of the triac by the trickle current through the diac.
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Click para ampliarLight Modulator
The light seem to dance in time with the music. Line-voltage lamps of about 40 to 100 W do nicely. The current for the lamp is from an SCR. When low-level audio is present across T1, SCR1 is not triggered into conduction. A louder signal, however, triggers the SCR so that the lamp lights and follows the sounds.
Since SCR1 is operated by an alternating current, the rectifier moves out of the avalanche condition when the gate current is low. Potentiometer R3 lets you adjust the power reaching transformer T1, so that with normal operating volume, SCR1 triggers again and again, except during quiet passages.
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Since SCR1 is operated by an alternating current, the rectifier moves out of the avalanche condition when the gate current is low. Potentiometer R3 lets you adjust the power reaching transformer T1, so that with normal operating volume, SCR1 triggers again and again, except during quiet passages.
Click para ampliarLight Controller
LED Brightness Control
The brightness of LED display is varied by using a photocell in place of one timing resistor in a 555 timer, and bypassing the other timing resistor to boost the timer's maximum duty cycle. The result is a brighter display in sunlight and a fainter one in the dark.
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Click para ampliarDC Lamp Dimmer
A low power, low cost dc lamp dimmer for a two-wire portable "flashlight" can be realized with little or no heatsinking. In addition, a single potentiometer, R3 adjusts lamp brightness. Battery power is stored in C1 for U1, which is a free-running multivibrator whose frequency is determined by R1, R2, R3, R4, and C2. U1 drives the gate of Q1, turning it and the lamp ON and OFF at a rate proportional to the multivibrator duty cycle.
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Click para ampliarAutomatic Light Controller For Carport
A 555 timer IC, operating in the one-shot mode, is triggered by light striking photoresistors. These normally have a resistance of several megohms but, in the presence of light, that resistance drops to several hundred ohms, permitting current from the six-volt source to flow in the circuit. The R-C combination shown gives an on-time of about two minutes. Photoresistors PC3 and PC4 are mounted at headlight-height. When headlights illuminate the photoresistor, the timer starts. That actuates a relay, RY1, and the lights are turned on. The lights are automatically turned off when the timer's two minutes are up.
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Click para ampliar120 AC Shimmering Light
You can turn any ordinary household bulb into one that shimmers or blinks. This circuit works on any incandescent light up to 200 W, and runs on standard 120 Vac. The circuit uses an SCR to cause an ordinary lamp to shimmer. Note that one side of the lamp is connected directly to 120 Vac, and the other side of the lamp goes to the cathode of the SCR. As ac voltage is brought into the circuit through the line cord, it is full-wave rectified by diodes D1 and D2. That changes the ac to dc, and a portion of that dc voltage is applied to capacitor C1 through R2. Diode D3 blocks the (+) dc voltage so that only the voltage from the path of R1 and D3 is clear.
That forms an oscillator, which has a frequency determined by the setting of potentiometer P1 (because the other components have fixed values). Remember to use EXTREME CAUTION when using a device that connects to the ac line. NEVER use it outside or near water and always mount the entire kit inside a wooden or plastic (insulated) box to prevent any contact with the ac voltage.
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That forms an oscillator, which has a frequency determined by the setting of potentiometer P1 (because the other components have fixed values). Remember to use EXTREME CAUTION when using a device that connects to the ac line. NEVER use it outside or near water and always mount the entire kit inside a wooden or plastic (insulated) box to prevent any contact with the ac voltage.
Click para ampliarStrobe Alarm
This strobe gives a visual indication of a sensor input. The input signal causes U1, a light dependent resistor, to charge C1 and C3 through R4. When NE1 fires, C3 discharges into SCR1, which triggers it and causes C2 to discharge through trigger transformer T1, which triggers Flashlamp FL1. The 330-V supply should have about 50 to 100 uF output capacitance. L1 supplies about 25-mH inductance to prolong the flash and the life of FL1.
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Click para ampliarSeries SCR Lamp Flasher Handles a Wide Range Of Loads
Brief full-power flashes are obtained when the SCR conducts during positive half cycles of the line voltage. The SCR fires when the voltage at the divider, R3 and R4, reaches the gate-firing level. Diode D1 conducts during the reverse cycle of the SCR and provides preheating current to the lamp filaments.
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Click para ampliarSequential Led Flasher With Reversible Direction
Low Frequency Lamp Flasher/Relay Driver
This circuit is a low frequency warning device. The output of the oscillator is a square wave that is used to drive lamps or small relays. The circuit alternately flashes two incandescent lamps.
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Click para ampliarFlash Signal Alarm
This circuit is useful if you need a low-energy flashing alarm. The 200 to 400-dc supply should have enough internal resistance to charge the 0.5 uF capacitor between flashes, about 2 or 3 time constants, which means about 500k to 1M for a 1-s rate. Use lower values for higher rates.
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Click para ampliarDark Activated Led Flasher
This circuit can be used as a small beacon or marker light, and toys or novelty items. R1 is an LDR that has >= 10 k dark-resistance, or a CDS photocell. C1 determines the flash rate.
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Click para ampliarAlternating Led Flasher
The alternating LED flasher is simply a two-transistor oscillator with LEDs connected to the collector of each transistor, so that they light in time with the circuits oscillations.
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Click para ampliar3 Channel Color Organ
The ac line power is brought back into the circuit through F1, a protective 5-A fuse. One side of the ac line is connected to one side of each ac outlet. The other side of the ac line is connected to each SCR or silicon-controlled rectifier. Each SCR is, in turn, connected to the other side of each ac outlet. An audio signal is brought into the circuit from a stereo speaker by transformer T1. This transformer has 500-ohm impedance on the primary and 8-ohm impedance on its secondary. Connect T1 so that the 8-ohm side is connected to the speaker and the 500-ohm side is connected to potentiometer P1. Potentiometer P1 is used as a level or sensitivity control. The signal from its wiper lead is applied to each RC filter stage. Because each SCR has a different RC (resistor/capacitor) filter on its gate lead, each will respond to different frequencies. The greater the capacitance in the filter, the lower the frequency that the SCR will respond
to.
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to.
Click para ampliarVariable Strobe Light
In this strobe-light, two circuits are needed; one circuit charges a capacitor placing 320 Vdc between the cathode and anode of the flashtube. The other circuit provides bursts of approximately 4000 V to trigger the flashtube into conduction. The voltage-doubler works by summing two equal voltages in series, which results in a doubling of the voltage. The 4000 V needed to trigger the flashtube is provided by transformer T1--a voltage step-up transformer that develops 4000 V across its secondary coil when current flows in the primary coil. Silicon-controlled rectifier SCR1 controls the current flow in the primary coil of T1. When SCR1 conducts, current flows suddenly in the primary coil and 4000 Vac spikes appear across the secondary coil. For conduction, SCR1 needs a negative and positive voltage on the cathode and anode, respectively, and a positive voltage on the gate. It is the function of components R2, R3, C3, and NE1 to provide that positive gate voltage and turn on SCR1. Potentiometer R2, resistor R3, and capacitor C3 form an RC timing circuit. Control of charging time of C3 is accomplished by varying that resistance in the circuit. When the voltage on C3 reaches the firing voltage of the neon bulb, it causes NE1 to conduct, thus placing a positive voltage, from C3, on the gate of SCR1. The SCR now turns on and C3 discharges through SCR1 and the primary coil of T1. The 4000 V that is developed across the secondary coil of T1 fires the xenon tube, causing a bright flash. The whole process then repeats itself with C3 charging up, NE1 firing to short out SCR1, and T1 developing 4000 V to trigger the xenon flashtube.
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Click para ampliarDisco Strobe Light
This circuit uses a voltage doubler CR1 and CR2 to obtain about 280 V dc across C1. C2 and R3 form a voltage divider to obtain a dc voltage to change C3 through R2. When CR3 fires, a high voltage is generated in T1, firing L1.
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