Elektrokit

Shankar Nagar, Nagpur, Maharashtra

Port 1 of the controller (AT89C4051) is used as the data lines for the LCD (starting from pin 7- pin14 of LCD). Here using a 16 x 2 lines LCD display. In the first line, display "DAY" and "DATE", in the second line, i am displaying "TIME" with am/pm. Port 3 is used for the clock setting and it also provides the necessary control signals for the LCD. As shown in the diagram, switch3 will be used to select the parameter which need to be changed, switch 1 and 2, are used to increase or decrease the selected parameter value. When the power supply is switched on it will give you the default date and time, but later you can change it to the desired value. The source code for the project is written in C-language, and compiled using Keil C compiler. The schematic contains the power supply module also, which is not shown in the figure above. It is Microcontroller based (89C4051) LCD 16x2 display clock with day, date and time. We are into manufacturing and supplying Microcontroller Based Digital LCD Clocks nationwide.

Auto On/Off Timer is a simple and inexpensive timer, widely used to switch on/off devices. Auto On/Off Timer has a settable timing between 3min to 30min. The circuit is built around counter IC4060 (IC1) and inverter IC4049 (IC2). The circuit switches on automatically when power is on, and it switches off when the settable time is over.

About the Circuit :   IC1 has on-chip oscillator whose frequency is determined by external RC network connected to pins 9, 10 and 11. When power is on, pulse at junction R4-C2 resets the counter and counting starts. The output at pin3 of IC1 is low, which is given to inverter input pin3 of IC2. This low voltage input becomes high at the output of inverter at pin2. Transistor T1 turns on and relay is energized. T1 remains on until output at pin3 of IC1 becomes high. When the counting reaches to last bit or the time is over, output at pin3 of IC1 becomes high. As a result, the pulse at pin2 of IC2 goes low and T1 turns off. At the same time relay becomes off and it remains off until pin3 of IC1 goes low again. Here LED D1 and D2 are used to give visual indication. D1 gives the indication of timing pulse generation, whereas glowing of D2 indicates timer on indication. Calibration: The time delay between 3min to 30min is set with the help of preset P1.

The washing machine having no automatic controls can be atomized to some extent by the circuit below. This is helpful in saving power and improving washing quality. In addition, it makes the homemaker free to do other chores while washing machine is doing its job. The timer gives audible warning continuously when the time is over.

About the circuit :Washing Machine Timer is built around IC 4060 and inverting buffer 4049 both CMOS. Washing Machine Timer has on chip oscillator circuit, which can be finished by using external R, C components. C1, Rx*, R7 and VR1 forms the oscillator’s RC components which decides frequency and hence timing. C2, R11 provides power ON reset. Lower the frequency, higher the pulse timing. The oscillator frequency is divided by chain of 14 binary counters, which at the end of 14th stage, gives large pulse period at pin 3. Initially this output would be LO.
Once the circuit power is switched ON through S1, IC-1 gets reset and starts with all counter outputs reset to LO state. Counter outputs go Hi as counting progresses.
As the oscillator, frequency is divided and consecutive counter output goes high, the Hi state progresses through 14 stage counter outputs. LED D1 shows the oscillating behavior by pulsating flashes.  
When last counter output (Q14 at Pin 3) switches Hi, transistor T1 conducts and counter input at pin 11 is pulled LO.The output pin 3(last output of counter chain) is fed to the four inverting buffers (Ic 4049) which produces LO output at corresponding four outputs. Pin 2, 4 and 10 are connected in parallel to augment the drive capacity and drives a PZT buzzer. Fourth output at pin 6 drives the Relay through transistor T2 subsequently driving the washing machine through relay contacts.
Since initially 4049 output is Hi relay is energized as soon as power is applied to the circuit through S1. After the set time delay IC 4049 outputs go LO and relay is switched OFF thereby stopping the washing machine.
The time delay as per requirement can be selected by selecting resistor R1 to R6 with the help of rotary switch (one pole, 7way). Seven time delays are available to choose from. The time delay ranges can be altered by changing these resistance values.    

Select washing time bet.2 1/2 to 30 min. & buzzer when time laps.

PC Based On/Off Timer makes the circuit ON and OFF according to the ON time and OFF time. This is the most useful PC Based ON/OFF timer which uses a simple program written in C language and interface circuit using monostable multivibrator as shown in the circuit diagram. It has industrial as well as household applications. In addition it is very cost effective and most suitable for those who have a PC at workplace or home. In the program, you have the provision to enter the time the time in minutes as well as in seconds. Then it will ask for ON time and OFF time to control the appliance. Accordingly appliance will remain ON and OFF.

About the Circuit :

• The circuit for interfacing the PC’s parallel port with the load is very simple. It uses two ICs, one is for triggering and other used for monostable operation. The glowing of LED D3 indicates the triggering of monostable multivibrator designed using IC2. Whereas glowing of LED D2 indicates the ON/OFF condition of relay. Transistor T1 is used as a relay driver. The program code is written in ‘C’ language and compiled using ‘Turbo C’ compiler. When the program is run, it prompts the user to input the time duration in seconds or minutes to control the appliance. After entering the required timing, press any key from the keyboard. Suppose you input the total duration as‘t’ minutes, of which ‘on’ and ‘off’ durations are ‘t1’ and ‘t2’ minutes respectively. The program will repeat the on-off cycle for t/(t1+t2) number of times. After completion of the total time, to repeat the cycle, you will have to reset the time in the program to activate the circuit.  
• The program uses two bytes for storing integer data type. So when input is given in terms of seconds or minutes, it can hold 65, 535 seconds or 18 hours at the maximum. The sleep( ) function in the program is used to hold the appliance in ‘ON’ and ‘OFF’ periods as entered by the user against prompts. The sound function is used to give a beep during ‘ON’ condition of the appliance.
• When program is executed following messages are displayed on screen: “This is the program of ON/OFF Timer” “The circuit provides delay in seconds and minutes” “Press any key to continue…”    
• After pressing any key the program gives following messages: “Enter your choice to set the time duration. Enter time duration in minutes (press m). Enter time duration in seconds (press s)
• After pressing ‘m’ through keyboard, the program asks, “Enter the total time duration (in minutes): Enter the time to keep the circuit ON (in minutes): Enter the time to switch OFF the circuit (in minutes): Press any key to start the program…”   After pressing any key, the program generate control signal at port-2. The circuit is triggered and relay is on. While circuit is ON the program gives message as: “Your circuit is ON”   After ON time is over, the relay becomes OFF and the following message is displayed on screen: “Your Circuit is OFF”. If the total time duration is greater than the sum of ON time and OFF time, then the above cycle repeats. The time is entered in seconds then also the above messages displayed, only change is that in time duration is entered in seconds. At the end program displays the message as: “Your program completed successfully.”

Logarithmic Timer provides an effective way to show the periods of 5 to 15 minutes using ten LED display. Logarithmic Timer is based on the display driver IC1. The display is in the form of ten LEDs, which glows one by one or dot mode, indicating the lapse of time. Logarithmic Timer is also possible to show the display in bar mode through toggle switch S2.

About the Circuit :IC1, which is display driver IC has logarithmic scale. The resistor network R6-P1-C1 is used for time measurements. The voltage across this network has while C1 is being charged an exponential character when this is applied to IC1, which takes its logarithm. The time is shown linearly on the display. The values of P1 and R6 have been chosen to enable the timer showing periods of 5 to15 minutes.

The timer is reset (C1is discharged) when S1 is closed. Resistor R1 limits the peak value of the discharged current from C1 to an acceptable value for the switch contacts.
Resistor R5 compensates the leakage currents of the electrolytic capacitors to obviate the risk of D10 going out.If S2 is open, the display is in the dot mode. The elapsing of time is then shown by only one LED light. After a reset, D1 will light and then sequentially all other LEDs.
The total current drawn by the timer is 20mA, so the battery supply is possible. When S2 is ON, the display is in the bar mode. After a reset, all LEDs will light and then go out in turn, starting with D1. In this mode, battery supply is not recommended.