Schematic Rise

Wednesday, October 29, 2014

Fog Lamp Sensor Circuit Diagram

Here are simple Fog Lamp Sensor Circuit Diagram. For several years now, a rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under foggy conditions.

Circuit diagram :

Fog Lamp Sensor Circuit Diagram

When this fog lamp is switched on, the fog lamp of the pulling vehicle must be switched off to avoid irritating reflections. For this purpose, a mechanical switch is now built into the 13-way female connector in order to switch off the fog lamp of the pulling vehicle and switch on the fog lamp of the trailer or caravan. For anyone who uses a 7-way connector, this switching can also be implemented electronically with the aid of the circuit illustrated here.

Here a type P521 optocoupler detects whether the fog lamp of the caravan or trailer is connected. If the fog lamp is switched on in the car, a current flows through the caravan fog lamp via diodes D1 and D2. This causes the LED in the optocoupler to light up, with the result that the phototransistor conducts and energises the relay via transistor T1. The relay switches off the fog lamp of the car.

For anyone who’s not all thumbs, this small circuit can easily be built on a small piece of perforated circuit board and then fitted somewhere close to the rear lamp fitting of the pulling vehicle.

Author :Harrie Dogge - Copyright : Elektor

Thursday, October 16, 2014

Simple Sound Activated Lamp Relay Switch

This simple Sound-Activated Lamp circuit shown int the schematic diagram actives the switch using sound. We can use this circuit for various applications, such as automatic (sound-controlled) disco light or car’s LED light show. The Q1 amplify the audio from mic. The R1 is used to adjust the peak of signal to greater than about 0.7 volts, act as sensitivity adjuster. A certain level, the signal coming from microphone, after amplification by Q1, will trigger the SCR and light lamp I1. If we change the lamp with a relay, then we can get a sound-activated relay/switch, which can be used to control more powerful / high wattage high voltage lamps. If we use a relay, place a 1N4007 diode in parallel with the relay coil to prevent the back-emf from relay coil destroying the SCR.

Sound-Activated Lamp Circuit Diagram

Friday, August 22, 2014

Versatile emergency lamp

Here is the schema diagram of a very versatile emergency lamp that can be operated in two modes (flasher and dimmer). The schema is based on the dual op-amp IC LM358.The dimmer and flasher mode can be selected by using the switch S1. In the dimmer mode the output of IC1b will be pulses whose width can be adjusted by using POT R3. Transistors T1 and T2 forms the driver stage which drives the lamp L1 according to the output of IC1b. In the flasher mode, output of IC1b will be a variable frequency pulse which can be adjusted by POT R3 to obtain 1 to 25 flashes from the lamp.

Right click and see the image

Notes.

* The schema can be assembled on a Vero board. * Use a 12V battery for powering the schema. * A heatsink must be fitted on transistor T2. * S2 can be used as an ON/OFF switch. * F1 should be a 2A fuse. * L1 can be a 12V; 2A incandescent lamp. * IC1 must be mounted on a holder.

Wednesday, August 13, 2014

Build a Varying Brightness AC Lamp Circuit

Varying Brightness AC Lamp Circuit, an SCR is used to slowly vary the intensity of a 120 volt light bulb by controlling the time that the AC line voltage is applied to the lamp during each half cycle.

Varying Brightness AC Lamp Circuit Diagram

Build a Varying Brightness AC Lamp Circuit

Caution:
The schema is directly connected to the AC power line and should be placed inside an enclosure that will prevent direct contact with any of the components. To avoid electrical shock, do not touch any part of the schema while it is connected to the AC power line. A 2K, 10 watt power resistor is used to drop the line voltage down to 9 volts DC. This resistor will dissipate about 7 watts and needs some ventilation.

Operation:
A couple NPN transistors are used to detect the beginning of each half cycle and trigger a delay timer which in turn triggers the SCR at the end of the delay time. The delay time is established by a current source which is controlled by a 4017 decade counter. The first count (pin 3) sets the current to a minimum which corresponds to about 7 milliseconds of delay, or most of the half cycle time so that the lamp is almost off. Full brightness is obtained on the sixth count (pin 1) which is not connected so that the current will be maximum and provide a minimum delay and trigger the SCR near the beginning of the cycle. The remaining 8 counts increment the brightness 4 steps up and 4 steps down between maximum and minimum. Each step up or down provides about twice or half the power, so that the intensity appears to change linearly. The brightness of each step can be adjusted with the 4 resistors (4.3K, 4.7K, 5.6K, 7.5K) connected to the counter outputs.

The schema has been built by Don Warkentien (WODEW) who suggsted adding a small 47uF capacitor from ground to the junction of the current source transistor (PNP) to reduce the digital stepping effect so the lamp will brighten and fade in a smoother fashion. The value of this capacitor will depend on the 4017 counting rate, a faster rate would require a smaller capacitor.