Night Light Saver V5.0

8/8/2019 Night Light Saver V5.0

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Night Light Saver V5.0

Introduction

The Saver V5.0 runs simple clock emulation program,

turns a night light on and off with preset time, say 19:00

to 22:00 everyday. The design features low cost, easy

installation, no battery backup and no EMI. The

AT89C2051 uses external oscillator generated by schmitt

trigger gate CD4093, ~680kHz. Reference frequency was

derived from 50Hz main line. Time setting only allows at

18:00 by pressing time set button once. If main line hasfailed, functioning LED will blink at high rate . Since there

is no battery backup, thus repressing the button is then

needed. The output is capable of driving say, a 25W

incandescent lamp.


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Circuit Description

The schematic of the SAVER V5.0 is depicted in Figure 1.


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Explanation of the circuit operation for each parts is as follows;

1)Transformerless direct supply: R1 and C1 forms a simple current

limitting AC source. D1 and D2 converts AC to DC with C2performing a reservoir. D3 limits voltage across the circuit to ~5V.

2)External oscillator: A reliable schmitt gate oscillator with R8 and

C5 produces clock approx. 680kHZ. One machine cycle is ~18us.

3)89C2051 circuits: C4, 33uF and R4, 10k forms a reset circuit that

need time for riasing logic at least two machines cycle. S1 is amomentary button for setting time to 18:00 by pulling P3.0 to logic

low. The functioning LED is connected to P3.7. Q2 is a small triac

MAC97A6, and is drived by Q1, PNP transistor sinking through P1.7.

4)Reference frequency: R3 and C3 integrates a 50Hz main

frequency and unwanted transients producing triangle-like

waveform which is fed to U2 schmitt gate. The output pin4 is clean

50Hz square wave tied to int0.


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Explanation of the circuit operation for each parts is as follows;

1)Transformerless direct supply: R1 and C1 forms a simple current

limitting AC source. D1 and D2 converts AC to DC with C2performing a reservoir. D3 limits voltage across the circuit to ~5V.

2)External oscillator: A reliable schmitt gate oscillator with R8 and

C5 produces clock approx. 680kHZ. One machine cycle is ~18us.

3)89C2051 circuits: C4, 33uF and R4, 10k forms a reset circuit that

need time for riasing logic at least two machines cycle. S1 is amomentary button for setting time to 18:00 by pulling P3.0 to logic

low. The functioning LED is connected to P3.7. Q2 is a small triac

MAC97A6, and is drived by Q1, PNP transistor sinking through

P1.7.4)Reference frequency: R3 and C3 integrates a 50Hz main

frequency and unwanted transients producing triangle-like

waveform which is fed to U2 schmitt gate. The output pin4.


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Software

Saver5.hex is HEX file suitable for Easy-Downloader V1.1 for

writing the code to the chip. This file sets time to 18:00 whenpress S1 once. Time on and off is set to 19:00 to 22:00 everyday.

And finally the reference main frequency is 50Hz!! The original

source program SAVER5.C was written in 'C' language. User may

change set time when press S1 and change time on/off. It is a good

idea to include peak shaving period, say 20:00 to 20:30 depending

on living area. By placing timeOn3 and timeOff3 in the function

comparetime(), see the source program. To recompile the source

file you need a Micro-C Compiler from Dunfield Development

System with tiny memory model and need some modification ofthe runtime file by putting external interrupt is clean 50Hz square

wave tied to int0.

service routine that increments cputick variable


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Installation

The Saver may be built-in any kind of lamp fixtures. Figure 2 shows

the author's concept for building-in a 25W lamp fixture.

under preparation

Figure 2: The author's concept lamp fixture with built-in Saver

circuit

Although the Saver can operate even wrong connection of L and N to

the circuit. The author suggests to correct AC line connection to L and

N of the circuit. After finished installtion, turn the main switch on,

functioning LED will blink at high rate. Let try press S1 once, the lamp

will turn on 1 minute then off. The Saver assumes the current time is

18:00. Then wait for the clock at your home reachs 18:00, press S1

again.

Note that everytime you press S1, the lamp will turn on 1 minute only

once. The day after the lamp will then turn on and off at preset time.

Functioning LED will blink at low rate indicating normal operation.

If high blink rate is noticed when return home, power failed should

happen, no problem just wait again 18:00 then press S1. If the LED is

not blinked, someone may turn main switch off, turn it back on again

and wait for 18:00.


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Energy Saving Lamp

The Saver was not designed for turning such

energy saving lamps on and off. They mostly

use internal high frequency inverter. I have

been tested with one from National, it works!!

But I am not guarantee for your energy saving

lamp. I would be grateful if you could test and

let me know the result.


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Components Listing

1. C1 0.44 uF 250Vac AC capacitor

2. C2 330 uF 25V electrolytic capacitor

3. C3 1uF 16V nonpolar polyester capacitor4. C4 33uF 16V electrolytic capacitor

5. C5 50pF disceramic capacitor

6. R1 50Ohm 1/4W resistor

7. R2 1M 1/4W8. R3,R4,R8 10k 1/4W

9. R5 220Ohm 1/4W

10.R6,R7 1k 1/4W

11.D1,D2 1N4007 rectifying diode

12.D3 zener diode 5.1V 1/2W13.D4 small LED

14.Q1 2N2907 PNP transistor

15.Q2 MAC97A6 triac

16.U1 AT89C2051 Flash Microcontroller

17.U2 CD4093 schmitt nand gate

Documents

Night Light Saver V5.0