Timer Circuits

This simple circuit is a good solution to the powering a dual supply op amp from a single battery problem. The circuit simply takes a positive voltage and inverts it. It uses only one 555 timer and a few other passive components, so it doesn`t add much in the way of size and cost to a project...

Views: 2088 | Votes: 1 | Comments: 0 | Rating: 7 | Rank: 4 | Added: Jan 12, 2013 |

This over/under voltage cut-out will save your costly electrical and electronic appliances from the adverse effects of very high and very low mains voltages. The circuit features auto reset and utilises easily available components. It makes use of the comparators available inside 555 timer ICs. Supply is tapped from different points of the power supply circuit for relay and control circuit operation to achieve reliability. The circuit utilises comparator 2 for control.....

The choice of material to read or drive is the definition of three digits (Bit), RA0, 1,2 PORTA of the PIC at the entrance of 74HC138A. To select a material for reading or driving an output of 78HC138 is '0 '(Low), forcing the transistor (2SA1015) to conduct and thus is the material with the feet of PORTB. This function ensures that there will never be found simultaneously connected to PORTB two materials, since the remaining transistors are off. Switches BCD (inputs), the.....

A rising edge on the Trigger input starts a delay timer. At the end of the delay period Output 1 goes high and a second delay timer is started. At the end of the second delay Output 2 goes high. This is repeated for Outputs 3 and 4. The result is four outputs that go high in sequence with user defined delays between each one. Once Output 4 has gone high, a high level on the Reset input causes all four outputs to clear and the program goes back to the initial state.....

IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15 is taken low through the "Fire" button. IC2 then sequences through outputs Q1 to Q7, to feed power transistors TR1 to TR4, which fire electromagnets L1 to L4 in rapid sequence...

Using a single 555 Timer IC and a small transformer to generate a high voltage, this circuit will test zener diodes of voltage ratings up to 50VDC. The 555 timer is used in the astable mode, the output at pin3 drives a small audio transformer such as the LT700. This has a primary impedance of 1K and a secondary impedance of 8 ohms. Used in reverse the unloaded ac voltage is around 120volts ac...

The position encoder in Figure 1 is a simple yet powerful circuit that converts the change in resistance of a potentiometer into a digital value without using an expensive A/D converter. The working principle is a resistance-to-PWM converter built around the common 555 timer IC. A change in the potentiometer`s resistance causes a proportional change in the duty cycle of the timer`s output, which essentially encodes the resistance values as a PWM signal...

A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable circuit in contacts [ A ] and [ B ]. The circuit is based on IC1 (4060), which include in his inside, oscillator and a binary divider of 14 stage. The frequency operation of oscillator is determined by a circuit R-C.....

For use in a bathroom or car. I`ve seen similar circuits used in plastic pot-pourri containers...

Build a timer with Motorola Nitron MCU and using ICC08 to develop c program. Loader schematic also included. New s-record for 8-pin 68HC908QT2! The fan has mechanical timer for 0-180mins. One day it broken. So I got the idea to use Nitron chip to replace the mechanical timer. Someone may ask me why so complicated timer made by microcontroller chip? Actually we can build a timer with 555 and a 14-stage cmos counter! The 555 runs astable with time constant controlled by RC.....

Light emitting diodes are advan- tageous due to their smaller size, low current consumption and catchy colours they emit. Here is a running message display circuit wherein the letters formed by LED arrangement light up progressively. Once all the letters of the message have been lit up, the circuit gets reset. The circuit is built around Johnson decade counter CD4017BC (IC2). One of the IC CD4017BEs features is its provision of ten fully decoded outputs, making the IC.....

A wide rage auto turn OFF timer covering 1 minute to 20 hours in three ranges with S1. As soon as power is applied to the circuit the IC1 [555] starts to oscillate happily and feeds clock pulses to the IC2 [4017]. The IC2 [4017] and IC3 [4020] give a combined count rate of 81920 before the output of the IC3 [4020] goes high and turns Q1 on. With pot RV1 adjust the Time. ..

The resulting timer circuit is made from a CD4060, includes an oscillator and a 14 stage binary counter, two CD4040's, which are 12 stage binary counters, a CD4012 Dual Nand gate and a CD4013 Dual D Latch. The CD4060 is connected to a 32768 Hz ECS 3X8 tuning form crystal. The 10 Meg Ohm resistor between CD4060 pins 10 and 11 are to bias the internal inverter into its analog region, and the 330 K resistor in series with the crystal is to limit the power to the crystal......

The circuit uses independent timers to flash two light emitting diodes. Any time that light emitting diode D1 is lit__light emitting diode D2 will be switched off. Light emitting diode D3 is on if both D1 and D2 are off. Two versions of the circuit are shown. The second circuit uses fewer components by taking advantage of the bipolar outputs of the timers...

A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts specified. The current capacity of the circuit is only limited by what kind of relay you decide to use...

A very regular configuration of the 555 astable timer to work as a timer to trigger an alarm or any other equipment connected to pin 3. R resistor should be replaced with a potentiometer that will change the time delay. Capacitor C should be calculated too (there are many 555 calculators around internet).Is a common design, not very accurate but very usefull in many everyday aplications...

Views: 2699 | Votes: 1 | Comments: 0 | Rating: 7 | Rank: 1 | Added: Dec 19, 2012 |

I am very happy to use sdcc for writing firmware of my project. The compiled code is very compact and nice. After I succeeded writing a new firmware of xtimer and Easy-downloader V1.1 with sdcc. I cannot stop preparing a new page that gives the idea how to use sdcc and of course it`s time to renovate my old project with orcad. For now I can design the hardware, draw a schematic, write the firmware and layout the pcb. So I think why shouldn`t begin with Easy-Downloader......

This is basically a flasher circuit modified to turn on and off a bulb instead of a LED. It uses a 555 timer IC working as an astable multivibrator. The flashing rate can be varied from very fast to a maximum of once in 1.5 sec by varying the preset VR1...

This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared by IC2A & IC2B and monitored by LED D4. When D4 illuminates, albeit for a very short peak, IC3 is reset and restarts its counting. Pin 2 of IC3 remains in the low state, the two transistors are on and the relay.....

This circuit uses a simple 4060 IC oscillator/timer that is reset periodically by a computer. Should the computer fail to send a pulse, the output changes state. The time can easily be set from seconds to hours...