Circuit electrinic

You can take this white LED-based night lamp on your picnic outings. The lamp has sound trigger and push-to-on facilities and gives ample light during a walk at night. It will also prove useful in locating the door of your tent in the darkness. A click of the fingers will switch on the lamp for three minutes to help you in a strange place. The circuit uses low-power ICs to save the battery power. JFET op-amp TL071 (IC1) amplifies the sound picked up by the condenser microphone. Resistor R1 and low-value capacitor C1 (0.22µF) make the amplifier insensitive to very low-frequency sounds, eliminating the chance of false triggering. VR1 is used to adjust the sensitivity of the microphone and VR2 adjusts the gain of IC1. The amplified output from IC1 is coupled to trigger pin 2 of IC2, which is a monostable multivibrator built around low-power CMOS timer IC 7555.

Resistor R4 keeps trigger input pin 2 of the monostable normally high in the absence of the trigger input. Timing elements R6 and C4 give a time delay of three minutes. Reset pin 4 of IC2 is connected to the positive rail through R5 and to the negative rail through C2 to provide power-on-reset function. The output of IC2 powers the white LED (LED1) through ballast resistor R7. The circuit can be easily assembled on a perforated board. Make the circuit assembly as compact as possible to enclose in a small case. Use three 1.5V pen-light cells to power the circuit. Adjust VR1 and VR2 suitably to get sufficient sensitivity of IC1. Toggle switch S1 can be used to switch on the lamp like a torch.

Compact, transformerless circuitry No relays employed

Due to the low current drawing, the circuit can be supplied from 230Vac mains without a transformer. Supply voltage is reduced to 12Vdc by means of C1 reactance, a two diode rectifier cell D1 & D2 and Zener diode D3. IC1A, IC1B, R2, R3 and C3 form a reliable bounce-free toggle switch operated by P1. R4 and C4, wired to pin #6 of IC1B reset the circuit (lamp off) when power supply is applied. IC1C and IC1D wired in parallel act as a buffer, driving the Gate of the Triac through R5.

Circuit Diagram :

 230Vac Lamp Toggle Switch Circuit diagram

Parts:

R1____________470R   1/2W Resistor
R2_____________10K   1/4W Resistor
R3,R4_________100K   1/4W Resistors
R5______________1K   1/4W Resistor

C1____________330nF  400V Polyester Capacitor
C2____________100µF   25V Electrolytic Capacitor
C3____________100nF   63V Polyester or Ceramic Capacitor
C4_____________10µF   25V Electrolytic Capacitor

D1,D2________1N4007 1000V 1A Diodes
D3_________BZX79C12   12V 500mW Zener Diode
D4__________TIC206M  600V 4A TRIAC

IC1____________4011 Quad 2 Input NAND Gate CMos IC

P1_____________SPST Pushbutton

Note:

he circuit can be wired permanently to the mains supply as current drain is negligible.

Due to transformerless design there is no heat generation.

Low Gate-current Triacs are recommended.

Obviously, other appliances can be powered in place of a lamp, provided their power dissipation does not exceed about 400W @ 230V

110-120Vac operation is easily obtained by simply changing C1 value to 680nF 250V. No further changes are necessary.

In some cases, e.g. when the controlled device is far from the toggle switch, a pilot LED could be necessary for monitoring purposes. If so, disconnect pin #10 of IC1C from pin #11 of IC1D and wire a LED and its 1K series current limiting resistor across pin #10 of IC1C and negative supply.

Warning! The circuit is connected to 230Vac mains, so some parts in the circuit board are subjected to lethal potential! Avoid touching the circuit when plugged in and enclose it in a plastic box.

Source: www.redcircuits.com