Schematic Volt: controlled

Saturday, November 15, 2014

REMOTE CONTROLLED SWITCH CIRCUIT

This is a versatile remote controlled switch that can ON or OFF any appliance connected to it using a TV remote. IR remote sensor IC TSOP 1738 is used for receiving the signal. Normally when no signal is falling on IC3 the output of it will be high. This makes Q1 OFF. When a signal of 38 KHz from the TV remote falls on the IC3 its output goes low. This makes Q1 conduct and a negative pulse is obtained at pin 2 of IC 1 NE 555. Due to this IC1 wired as a monostable multivibrator produces a 4 Sec long high signal at its output. This high output is the clock for IC 2 which is wired as a flipflop and of , its two outputs pin 3 goes low and pin 2 goes high. The high output at pin 2 is amplified to drive the relay. For the next signal the outputs of IC2 toggles state. Result, we get a relay toggling on each press on the remote. Any appliance connected to this circuit can be switched ON or OFF.

Remote Controlled Switch Circuit Diagram with Parts List

Important Points

Before wiring the circuit make sure that the carrier frequency of the TV remote you have is 38 kHz. For that wire the sensor part only, point your remote to the TSOP1738 and press any switch. If output of TSOP1738 goes low then OK, your remote is of 38Khz type. Nothing to worry almost all TV remote are of this type.
You can use any switch of the remote because for any switch the code only changes, the carrier frequency remains same. We need this carrier frequency only.
Assemble the circuit on a good quality PCB or common board.
The appliance can be connected through NO or NC and C contacts of the relay.
Use a regulated 6V power supply for the circuit.

Saturday, October 25, 2014

Laser Controlled ON OFF switch

This Laser Controlled ON/OFF switch circuit is built around a 555 timer using very few components. Since the circuit is very simple, even a novice can easily build it and use it as a controlling device. A laser pointer, now easily available in the market, can be used to operate this device. This circuit has been tested in operational conditions from a distance of 500 meters and was found to work satisfactorily,though it can be controlled from still longer distances.
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Laser Controlled ON/OFF switch Circuit diagram :

Laser Controlled ON/OFF Switch Circuit Diagram

Aiming (aligning) the laser beam exactly on to the LDR is a practical problem. The circuit is very useful in switching on/off a fan at night without getting off the bed. It can also be used for controlling a variety of other devices like radio or music system. The limitation is that the circuit is operational only in dark or dull lit environments.

By focusing the laser beam on LDR1 the connected gadget can be activated through the relay, whereas by focusing laser beam on LDR2 we can switch off the gadget. The timer is configured to operate in bitable mode. The laser pointers are available for less than Rs 150 in the market. The cost of the actual circuit is less than Rs 50.

Author :Dr K.P. Rao - Copyright : EFY

Thursday, September 25, 2014

Voltage Controlled Oscillator Circuit

A simple voltage controlled oscillator circuit which produces both triangular and square wave outputs is shown.
Then the output of the Schmitt trigger is high, the clamp transistor TR; is conducting and the input current passing through R2 is shunted to ground. The current passing through R 1 causes a falling ramp to be formed. When the Schmitt circuit changes state, its output switches TR; to the nonconducting state. The current flowing through R2 can be made twice that flowing through Fl; (R2 = R;/2) so that the rising part of the ramp has a similar slope to the negative part. The greater the value of the control voltage, the greater the frequency of oscillation. However, the voltage must exceed the constant input voltage (V,) or the circuit will fail to oscillate.

Friday, August 29, 2014

Temperature controlled Fan

This schema adopt a rather old design technique as its purpose is to vary the speed of a fan related to temperature with a minimum parts counting and avoiding the use of special-purpose ICs, often difficult to obtain.

Temperature-controlled

Parts:

P1_____________22K Linear Potentiometer (See Notes)

R1_____________15K @ 20°C n.t.c. Thermistor (See Notes)
R2____________100K 1/4W Resistor
R3,R6__________10K 1/4W Resistors
R4,R5__________22K 1/4W Resistors
R7____________100R 1/4W Resistor
R8____________470R 1/4W Resistor
R9_____________33K 4W Resistor

C1_____________10nF 63V Polyester Capacitor

D1________BZX79C18 18V 500mW Zener Diode
D2_________TIC106D 400V 5A SCR
D3-D6_______1N4007 1000V 1A Diodes

Q1,Q2________BC327 45V 800mA PNP Transistors
Q3___________BC337 45V 800mA NPN Transistor

SK1__________Female Mains socket

PL1__________Male Mains plug & cable

R3-R4 and P1-R1 are wired as a Wheatstone bridge in which R3-R4 generate a fixed two-thirds-supply "reference" voltage, P1-R1 generate a temperature-sensitive "variable" voltage, and Q1 is used as a bridge balance detector.
P1 is adjusted so that the "reference" and "variable" voltages are equal at a temperature just below the required trigger value, and under this condition Q1 Base and Emitter are at equal voltages and Q1 is cut off. When the R1 temperature goes above this "balance" value the P1-R1 voltage falls below the "reference" value, so Q1 becomes forward biased, pulse-charging C1.
This occurs because the whole schema is supplied by a 100Hz half-wave voltage obtained from mains supply by means of D3-D6 diode bridge without a smoothing capacitor and fixed to 18V by R9 and Zener diode D1. Therefore the 18V supply of the schema is not true DC but has a rather trapezoidal shape. C1 provides a variable phase-delay pulse-train related to temperature and synchronous with the mains supply "zero voltage" point of each half cycle, thus producing minimal switching RFI from the SCR. Q2 and Q3 form a trigger device, generating a short pulse suitable to drive the SCR.

Notes:

* The schema is designed for 230Vac operation. If your ac mains is rated at about 115V, you can change R9 value to 15K 2W. No other changes are required.
* Circuit operation can be reversed, i.e. the fan increases its speed as temperature decreases, by simply transposing R1 and P1 positions. This mode of operation is useful in controlling a hot air flux, e.g. using heaters.
* Thermistor value is not critical: I tried also 10K and 22K with good results.
* In this schema, if R1 and Q1 are not mounted in the same environment, the precise trigger points are subject to slight variation with changes in Q1 temperature, due to the temperature dependence of its Base-Emitter junction characteristics. This schema is thus not suitable for use in precision applications, unless Q1 and R1 operate at equal temperatures.
* The temperature / speed-increase ratio can be varied changing C1 value. The lower the C1 value the steeper the temperature / speed-increase ratio curve and vice-versa.
* Warning! The schema is connected to 230Vac mains, then some parts in the schema board are subjected to lethal potential! Avoid touching the schema when plugged and enclose it in a plastic box.

Sunday, August 10, 2014

Phase Controlled Dimmer Wiring diagram Schematic

A phase-controlled dimmer delays the triac turn-on to a selected point in each successive ac half cycle. Use this schema only for incandescent lamps, heaters, soldering irons, or universal motors that have brushes.

Phase Controlled Dimmer Circuit Diagram