Battery powered Night Lamp Circuit

Ultra-low current drawing 1.5V battery supply

This circuit is usable as a Night Lamp when a wall mains socket is not available to plug-in an ever running small neon lamp device. In order to ensure minimum battery consumption, one 1.5V cell is used, and a simple voltage doubler drives a pulsating ultra-bright LED: current drawing is less than 500µA.
An optional Photo resistor will switch-off the circuit in daylight or when room lamps illuminate, allowing further current economy.

This device will run for about 3 months continuously on an ordinary AA sized cell or for around 6 months on an alkaline type cell but, adding the Photo resistor circuitry, running time will be doubled or, very likely, triplicated.

Circuit diagram :

 Battery-powered Night Lamp Circuit diagram

Parts:

R1,R2___________1M   1/4W Resistors
R3_____________47K   1/4W Resistor (optional: see Notes)
R4____________Photo resistor (any type, optional: see Notes)

C1____________100nF  63V Polyester Capacitor
C2____________220µF  25V Electrolytic Capacitor

D1______________LED  Red 10mm. Ultra-bright (see Notes)
D2___________1N5819  40V 1A Schottky-barrier Diode (see Notes)

IC1____________7555 or TS555CN CMos Timer IC

B1_____________1.5V Battery (AA or AAA cell etc.)

Circuit operation:

IC1 generates a square wave at about 4Hz frequency. C2 & D2 form a voltage doubler, necessary to raise the battery voltage to a peak value able to drive the LED.

Notes:

• IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less.
• If you are not needing Photo resistor operation, omit R3 & R4 and connect pin 4 of IC1 to positive supply.
• Ordinary LEDs can be used, but light intensity will be poor.
• An ordinary 1N4148 type diode can be used instead of the 1N5819 Schottky-barrier type diode, but LED intensity will be reduced due to the higher voltage drop.
• Any Schottky-barrier type diode can be used in place of the 1N5819, e.g. the BAT46, rated @ 100V 150mA.

Source :http://www.ecircuitslab.com

Read more

Automatic Bathroom Light with Back up Lamp Circuit Diagram

Sometimes we forget to switch off the bathroom light and it remains on unnoticed for long periods. This circuit solves the problem of electricity wastage by switching off the lamp automatically after 30 minutes once it is switched on. The back-up LED lamp provided in the circuit turns on for three minutes when mains fails. This is helpful especially when you are taking a shower at night.

The circuit is built around binary counter CD4060 (IC2), which has a built-in oscillator and 14 cascaded bistable multivibrators. The oscillator generates clock pulses based on the values of resistors R3 and R4 and capacitor C3.

Automatic Bathroom Light with Back-up Lamp Circuit Diagram

 

For the given values, Q11 output of IC2 goes high after 30 minutes of power-on. Resistor R2 resets the IC for proper operation. The output of IC2 is fed to the gate of the SCR via resistor R6 and LED2, which function as a voltage dropper as well as output status indicator.

When the SCR gets gate drive, it fires to energise relay RL1. The latching function of the SCR keeps the relay energised until the power to the circuit is switched off using switch S1. When the relay energises, its normally closed (N/C) contacts break and light turns off. LED1 indicates that the oscillator is working.

The back-up white-LED lamp comprising LED3 and LED4 gives ample light in the event of mains failure. It is powered by a 9V rechargeable battery, which is charged at around 200mA current via diode D6 and resistor R7 when the circuit is switched on.

The back-up lamp circuit is built around timer NE555 (IC3) designed as a monostable. The output of IC3 goes high for three minutes based on the values of preset VR1 and capacitor C9. When the circuit is switched on, IC3 gets power supply via diode D6 and its trigger pin 2 remains high due to resistor R8. As a result, its output remains low as long as mains is present.

When power fails, pin 2 of IC3 get striggered via capacitor C8 and the monostable output goes high to switch on the white LEDs (LED3 and LED4). Resistor R9 limits the current through the LEDs to a safe level. Diode D7 is forward biased to give full voltage to the monostable when power fails.

The power supply for the circuit is derived from a 15V AC, 250mA transformer. The secondary output is rectified by a full-wave rectifier comprising diodes D1 through D4. Capacitor C1 smoothes the resulting DC. Regulator IC 7812 (IC1) and capacitors C4 and C5 provide stabilised 12V for the circuit.

Assemble the circuit on a Vero board and enclose it in a watertight plastic case. Connect the bathroom lamp (either 25-watt bulb or 11-watt CFL tube) to the circuit via N/C contacts of the relay, so that it turns on when switch S1 is pressed. For easy access, fix switch S1 along with the neon indicator outside the bathroom.

Sourced By EFY Author D. Mohn Kumar

Read more

Power on Reminder with LED Lamp Circuit Diagram

D. Mohan Kumar is famous name in the circuits world. There are ds Power-on Reminder with LED Lamp Circuit Diagram creation. Many a times equipment at workstations remain switched on unnoticed. In this situation, these may get damaged due to overheating. Here is an add-on device for the workbench power supply that reminds you of the power-on status of the connected devices every hour or so by sounding a buzzer for around 20 seconds. It also has a white LED that provides good enough light to locate objects when mains fails.

Power-on Reminder with LED Lamp Circuit Diagram

 

 Fig. 1 shows the circuit of power-on reminder with LED lamp. Here, IC NE555  (IC1) is wired as an astable multivibrator, whose time period is set to around six minutes using resistors R1 and R2, preset VR1 and capacitor C1 for sounding the buzzer every hour. The output of IC1 is fed to the clock input of IC CD4017 (IC2). Capacitor C3 and resistor R3 provide power-on-reset pulse to IC2.When power to the circuit is switched on, pin 3 of IC2 goes high. After around one hour, its output pin 11 (Q9) goes high and the buzzer sounds. This cycle repeats until the two npn transistors. The LDR offers a very high resistance in darkness, i.e., when no light falls on it. Therefore when power fails, transistor T1 gets reverse biased to drive transistor T2 and the white LED (LED2) glows. The lamp circuit is powered by a 9V rechargeable battery, which is charged via resistor R5 when mains is present. Thus in darkness, the LED remains power to the circuit is switched off.

 The automatic lamp is built around a light-dependent resistor (LDR) and ‘on.’Fig. 2 shows the power supply circuit. The AC mains is stepped down by transformer X1 to deliver a secondary output of 15V AC at 500 mA. The transformer output is rectified by a bridge rectifier comprising diodes D1 through D4, filtered by capacitor C5 and regulated by IC 7812 (IC3) to provide regulated 12V to the circuit. Capacitor C6 bypasses any ripple in the regulated output.

Sourced By: EFY Author D. Mohn Kumar

Read more