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For a lower parts count than the 2 transistor multivibrators, 2 LED s can be alternately flashed with a 555 integrated circuit configured as shown in Schematic 2.  I chose the combination of a 2K2 and a 47K resistor to determine the oscillation frequency along with the 10 uF capacitor connected to pins 2 and 6. You can practically change the (R Speed) 47K value to between 10K and 100K or more. Greater resistance = lower speed. You may also wish to connect up a 100K or so potentiometer instead of the 47K resistor for a variable speed version. Additionally, the 10 uF capacitor value can be changed. Feel free to experiment. Although, alternately flashing LED s  is great for the beginner to electronics, the basic one ON, one OFF circuit gets boring quickly. In the next section, we will try to improve the look and try to approximate a flash like a police car (within limits).

Normally, the timer clocks we find in stores have to be plugged in to the electrical current to work. It becomes very difficult when you require something that works on batteries The best solution is to build yourself one. It is easy to turn an electrically operated timer into a battery operated timer. First of all, the timer has to be disassembled. This is pretty simple. All that is needed is to remove the screws that hold the back cover in place. The timer will then split. It must be separated carefully to avoid any damage on the screen or inner controls. Once it is disassembled, the original PCB should be removed completely, in order to gain access to the full back cover. Now the space is free, the only thing available is a totally useful space that comprises of the plastic marks and walls used to set and hold the original PCB. The plastic features can be removed by using a Dremel tool. It is highly recommended that some kind of mask or protection for eyes, nose and mouth should be ...

This timer circuit is designed to switch on a 12 V load in a solar-powered installation for a preset period at the press of a button. When the period has expired a latching relay disconnects both the load and the controller circuit from the 12 V supply. The length of the period can be configured by making suitable changes to the microcontroller’s source code. When button S1 is pressed a voltage appears across relay coil L1, and the relay switches the load on. Since the relay is a latching type, it remains in this state when the but ton is released. There is now a supply to the 78L05 voltage regulator (a low-dropout type such as the LP2950CZ-5.0 may also be used) and the microcontroller is powered up. In the microcontroller the timer program runs until the configured time interval has elapsed. Around 90 % of the way through the time period LED D2 lights as a warning that the load will shortly be switched off, and this time can also of course be configured by changing the software. When ...

Normally, the timer clocks we find in stores have to be plugged in to the electrical current to work. It becomes very difficult when you require something that works on batteries The best solution is to build yourself one. It is easy to turn an electrically operated timer into a battery operated timer. First of all, the timer has to be disassembled. This is pretty simple. All that is needed is to remove the screws that hold the back cover in place. The timer will then split. It must be separated carefully to avoid any damage on the screen or inner controls. Once it is disassembled, the original PCB should be removed completely, in order to gain access to the full back cover. Now the space is free, the only thing available is a totally useful space that comprises of the plastic marks and walls used to set and hold the original PCB. The plastic features can be removed by using a Dremel tool. It is highly recommended that some kind of mask or protection for eyes, nose and mouth should be ...

This is a Simple Timer with Musical Alarm Circuit Diagram.This low-cost timer can be used for introducing a delay of one minute to two hours. After the timing period is over, a musical song is heard. The circuit is built around popular CMOS oscillator/divider CD4060 (IC1). It works off a 9V PP3 battery and its standby current drain is very low.  Fig. 1: Pin configuration of melody generator ICUM66 By adjusting preset VR1, the time delay can be adjusted. After time delay is over, output pin 3 of IC1 goes high and npn transistor T1 conducts to provide positive power supply to melody generator IC UM66 (IC2) at its pin 2. Zener diode ZD1 reduces this power supply to 3.3V required for operation of IC2. The output of IC2 is fed to the loudspeaker (LS1) via driver transistor T1. Preset VR2 is used to control the volume of the loudspeaker.   Fig. 2: The circuit of timer with musical alarm The timer gets activated when power is supplied by pressing switch S1. To switch off the alarm, y...

Tiny Timer Light Switch presented here is a simple transistorised electronic timer which drives a high efficiency white LED for a finite time out. This circuit is very useful for in-car reading etc. The circuit works off 12 volt dc supply. After construction, fit the unit at a suitable location inside your car and power the circuit from the in-dash standard cigar lighter socket. The timer light switch is ultra simple, economic, straight forward and self explanatory. Timer light switch Circuit Diagram : the timer light switch works? Normally T1 is turned off by P1 and R2. When the trigger switch S1 is pressed the base of T1 is connected to the +12V supply via R2. Now T1 turns on and this action turns on the next transistor T2 which in turn energises the white LED (D2). Resistor R4 limits the operating current of white LED (D2). When the switch is pressed is current also flows into capacitor C1 (through R1) and charges it. So when the switch S1 is released the charge in the capaci...

This is a combination digital clock timer and solar panel charge controller used to maintain a deep cycle battery from a solar panel. The timer output is used to control a 12 volt load for a 32 minute time interval each day. Start time is set using 9 dip switches and ends 32 minutes later. The 32 minute duration is set by selecting the 5th bit (2^5 = 32) of a 4040 binary counter (pin 2). The timer also has a manual toggle switch so the load can be manually switched on or off and automatically shuts off after 32 minutes. The time duration can be longer or shorter (8,16,32,64,128,256 minutes etc.) by selecting the appropriate bit of the counter. The timer circuit is shown in the lower schematic just above the regulator.   Basic Clock Circuit diagram The basic clock circuit (top schematic below) is similar to the binary clock (on another page) and uses 7 ICs to produce the 20 digital bits for 12 hour time, plus AM and PM. A standard watch crystal oscillator (32,768) is used as the tim...

Circuit Diagram Description This circuit provides a visual 9 second delay using 10 LEDs before closing a 12 volt relay. When the reset switch is closed, the 4017 decade counter will be reset to the 0 count which illuminates the LED driven from pin 3. The 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 volts. When the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the 555 timer circuit to produce an approximate 1 second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with a larger capacitor or larger resistor at pins 2 and 6 of the 555 timer.  Source http://www.seekic.co...

Types of Timers in PLC | OFF Delay Timer (TOF)   PLC Timers are generally used for delaying an event from taking place, or to delay a device from shutting off either on an on transition or an off transition.   There are three types of PLC timers:   The Timer ON delay (TON), Timer Off delay (TOF), and the Retentative Timer On delay (RTO). By default, timers are stored in the T4 Data file, however other time files can be created. A timer consists of the following components:   Preset word (PRE), Accumulate word (ACC), Done bit (DN), Timer Timing bit (TT), and Enable bit (EN).   For Timers, the Enable bit follows the rung condition. The entire timer is addressed by it's element (example: T4:0) Pieces of the timer can be used in logic however such as the DN bit on an XIC (T4:0/DN), or the Accumulated value in a MOV statement (T4:0.ACC) PLC Timer Off Delay (TOF)   The Off Delay Timer is generally used to delay an event from shutting off.   Image a lube sy...