Circuit Wiring Solution: activated

Showing posts with label activated. Show all posts

Wednesday, October 8, 2014

LASCR Light Activated SCR circuit

LASCR or Photo SCR

Light activated SCR (LASCR) or a Photo SCR is just an ordinary SCR except that it can also be light triggered. Most LASCRs also have a gate terminal for being triggered by an electrical pulse just as a conventional SCR. The basic construction of an LASCR is shown in figure. The schematic symbols most commonly used for the LASCR are shown in figure. Some LASCRs have clear windows in their cases so that light sources from other devices can be coupled to them. Many have the light source encapsulated in the same package so that a relay is formed. When the light falling on depletion layers is strong enough, valence electrons are dislodged from their orbits and become free electrons. When these free electrons flow out of the collector of one, transistor into the base of the other.

LASCR Symbol

The positive feedback starts and the LASCR turns on just like a normal SCR, the LASCR will continue to conduct even if the light source is removed. For maximum sensitivity to light, the gate is left open, as shown in figure. Trigger adjust can be included if an adjustable trip point is desired as shown in figure. The gate resistor diverts some of the light produced electrons and alters the sensitivity of the circuit to the incoming light. The devices are for low power applications.

LASCR Applications

The LASCRs find many applications including optical light controls, relays, phase control, motor control and a large number of computer applications. The maximum current (rms) and power (gate) ratings for LASCRs commercially avail-able are about 3 A and 0.1 W. With the increase in junction temperature the light energy required to activate the device is reduced.

Relay with LASCR

Relay using LASCR

A solid-state relay using two LASCRs in reverse parallel is shown in figure. Two LASCRs are connected in reverse parallel so as to obtain conduction in both half cycles of the applied supply voltage Vg. A single light-emitting diode (LED) is employed for triggering both LASCRs. Bias resistors are used to control the light sensitivity of the gates and avoid sporadic triggering during off periods. Usually all the three active devices (two LASCRs and one LED) and the two bias resistors RG are encapsulated in the same package. Since the relay action does not require direct electrical connection, such relays are often used to couple signals into very high voltage equipment and other dangerous locations.

Friday, October 3, 2014

Electronic circuit uses a 555

The Electronic circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and emitter and the transistor switches on. A larger current flows in the collector electronic circuit enabling the 555 osillator to sound.

An On/Off switch is provided and remember to use a non-reactive metal for the probe contacts. Gold or silver plated contacts from an old relay may be used, however a cheap alternative is to wire alternate copper strips from a piece of veroboard.

These will eventually oxidize over but as very little current is flowing in the base circuit, the higher impedance caused by oxidization is not important. No base resistor is necessary as the transistor is in emitter follower, current limit being the impedance at the emitter (the oscillator circuit).

Saturday, September 13, 2014

Sound Activated Lights

This diy sound activated lights schema turns a lamp ON for a short duration when the dog barks (or a relatively strong sound) giving an impression that the occupants have been alerted. The condenser microphone fitted in a place to monitor sound and generates AC signals, which pass through DC blocking capacitor C1 to the base of transistor BC549 (T1). Transistor T1 along with transistor T2 amplifies the sound signals and provides current pulses from the collector of T2. When sound is produced in front of the condenser mic, triac1 (BT136) fires, activates lights and the bulb (B1) glows for about two minutes.

Sound Activated Lights Circuit Diagram

Assemble the sound activated lights schema on a general purpose PCB (schema board) and enclose in a plastic cabinet. Power to the sound activated switch schema can be derived from a 12V, 500mA step-down transformer with rectifier and smoothing capacitor. Solder the triac ensuring sufficient spacing between the pins to avoid short schema. Fix the unit in the dog’s cage or close to the sound monitoring spot, with the lamp inside or outside as desired. Connect the microphone to the sount activated lights schema using a short length of shielded wire. Enclose the microphone in a tube to increase its sensitivity.

Caution. Since the sound activated lights uses 230V AC, many of its points are at AC mains voltage. It could give you lethal shock if you are not careful. So if you don’t know much about working with line voltages, do not attempt to construct this schema. We will not be responsible for any kind of resulting loss or damage.

Tuesday, September 2, 2014

Light activated switch circuit

This schema is well important schema for us because We can get lots of advantages through this schema.When the light puts on L.D.R the schema activates.So you can use this one as you morning alarm or you can use this one for your robot.

Note

# You can use either a 12 V battery or a well regulated & filtered 12V DC mains operated power supply.

# The pin 5&6 (Balance & Balance/Strobe ) of IC LM311 are shorted to minimize the chance of oscillations.

Thursday, August 28, 2014

Dark activated LED or Lamp Flasher

This schema adopts the rather unusual Bowes/White emitter coupled multivibrator schema. The oscillation frequency is about 1Hz and is set by C1 value. The LED starts flashing when the photo resistor is scarcely illuminated. The onset of flashing can be set by trimming R2.

Dark-activated

Parts:

R1_________________Photo resistor (any type)
R2________________100K 1/2W Trimmer Cermet
R3,R4______________10K 1/4W Resistors
R5________________470R 1/4W Resistor
R6_________________47R 1/4W Resistor

C1________________220µF 25V Electrolytic Capacitor

D1______________1N4148 75V 150mA Diode
D2_________________LED Any type and color (See Notes)

Q1,Q2____________BC337 45V 800mA NPN Transistors

SW1_______________SPST Switch

B1__________________3V (Two 1.5V AA or AAA cells in series, etc.)

Notes:

* Best results in flashing frequency can be obtained using for C1 a value in the 100 - 1000µF range.
* To drive a filament lamp make the following changes:

Use a 2.2 to 3V, 250-300mA bulb in place of the LED
R2 = 10K 1/2W Trimmer Cermet
R3, R4 = 1K 1/4W Resistors
R6 = 1R 1/4W Resistor
C1 = 470 to 1000µF 25V Electrolytic Capacitor

* In LED-mode operation the stand-by current consumption is less than 400µA.
* In Lamp-mode operation the stand-by current consumption is about 3mA.