Tag Archives: Timer

Emon-server – 555 Timer as power usage sensor


by dkroeske @ github.com:

A cheap 555 timer chip acting as Schmitt trigger combined with a phototransistor or LDR is taped to the ‘flashing light’ or ‘pulsing magnet’ on the electricity meter. The output of the 555 timer chip is connected to one of the GPIO pins on the Raspberry Pi. A Python script (executing in the background) recording 555 events is calculating actual energy usage [e.g. Watt] every time the 555 is signaling and stores epochs in an SQLite3 database. From this, another Python script (executed from e.g. cron) generates all kinds of energy usage information (e.g. kWh or kWday or whatever). Using Node.js (running on the same Pi) all data is ‘RESTified’ enabling spreading out to the W3. To maintain privacy JSON web tokens are required every time the service is queried. Oh, and there is also a Pimatic plugin available (here)

Emon-server – 555 Timer as power usage sensor – [Link]

Dog Repellent Ultrasonic Circuit 2





When we hear the word “Ultrasonic” we often refer it to bats and dolphins communication. Technically, “Ultrasonic” applies to sound that is anything above the frequencies of audible sound, and includes anything over 20kHz. Frequencies used for medical diagnostic ultrasound scans extend to 10 MHz and beyond. This dog repellent ultrasonic circuit will chase away angry dogs. It comprises of a 555 timer IC, a speaker/piezoelectric and a little ferrite transformer.

The main part of this circuit is a 555 timer IC. A 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package. You can use the 555 effectively without understanding the function of each pin in detail. Frequently, the 555 is used in astable mode to generate a continuous series of pulses, but you can also use the 555 to make a one-shot or monostable circuit. The 555 can source or sink 200 mA of output current, and is capable of driving wide range of output devices.

To use this circuit adjust 4k7Ω Resistor at resonance frequency of the piezo transducer for maximum amplitude of the repeller ultrasonic sound. At 11 KHz to 22kHz this can reach a value of 10Vpp and the buzzer is a passive one (without generator).

Note: Ultrasonic frequency must be set with a dog nearby.


4k7Ω Resistor
10uF Capacitor
10nF Capacitor
1k2Ω Resistor
4k7Ω Potentiometer
NC Push Button

Dog Repellent Ultrasonic Circuit 2 – [Link]

1 to 100 Seconds Timer


This project is a timer project and build around popular 555 Timer IC, It can be used for all application required a delay of up to 100 Seconds. Onboard board preset to adjust the required timer duration in range of of 1 to 100 Seconds, Tact switch SW1 to reset the timer and SW2 to start the timer. LED D3 works as power indicator and LED D2 to indicate timer operation.

Load can be connected to CN1 Screw Terminal, Out-put has both the operation normally Open and normally closed. Circuits works on 12V DC and consume approx. 100mA current. Very useful project can be used in various applications like water irrigation system, Kitchen timer etc.

Supply input 12 VDC @ 100 mA
Onboard start and reset tactile switch
Relay output: SPDT relay
Relay specification: 5 A @ 250 VAC
Relay state LED indicator
Preset adjustable range function
Power-On LED indicator
Screw terminal connector for easy relay output connection
Four mounting holes of 3.2 mm each
PCB dimensions 48 mm x 63 mm

1 to 100 Seconds Timer – [Link]

Simple timer with PIC16F628A


This is a quick project for a timer. Recently I finished my UV light exposure box and thought that it will be convenient to have a build in timer to switch off the light after preset time. So I had a PIC16F628A lying around and after searching the web I found a Brazilian site (I think?) with tons of interesting projects with microcontrolers. This project is based on one of them.

The schematic uses the internal oscillator of the microcontroller which is enough accurate for my purposes, but as the pins 15 and 16 are left unoccupied, there can be connected external quartz resonator with better accuracy. As I said, this project is based on an existing project, but actually my schematic is quite different and the code was almost completely rewritten. My programming abilities are little rusty, but I think the final result is quite good.

Simple timer with PIC16F628A – [Link]

MAX6369 Series Watchdog Timers


The MAX6369-74 series watchdog-only supervisors are available in tiny SOT23-8 packages and have selectable watchdog timeout periods (1.7ms to 104s), start-up delays (1.7ms to 104s) and output pulse widths (1.7ms and 170ms) depending on the part selected and the state of 3 pins (SEL0, SEL1, SEL2). These parts have several advantages over the historical “555” solutions. As well as the lower supply current (20µA max instead of 120µA max at 5V supply) the overall solution takes much less board area with the smaller package and the absence of large timing resistors and capacitors.

MAX6369 Series Watchdog Timers – [Link]

ytimer, visual feedback timer


Here’s Aon’s finished project the ytimer a visual feedback timer:

A countdown timer with super bright 7-segment displays that flash when the time is up, instead (or in addition to) an audible alarm.
The design is based on a PIC16F886 microcontroller which drives the displays using a TLC5916 LED driver and dual P-channel MOSFETs. A rotary encoder with a push button is used for input, in addition to two microswitches, one for power and one for toggling sound. The sound switch also toggles a green 0603 indicator LED.
The device is powered from two AAA batteries, which will hopefully deliver adequate battery life.


ytimer, visual feedback timer – [Link]

555 Timer Breakout Board Plus


A breakout board for the 555 timer exposing the leads astable or monostable implementation.

Hello, my name is Patrick Grady and I’m a highschool senior in the US. I’m an avid programmer and tinkerer and love anything related to electronics and computers.

This past winter I took a class in Digital Electronics and was introduced to the 555 timer. One of the most common applications of the 555 timer is the astable mode, which is unfortunately rather clunky to build on a breadboard. This 555 breakout board does more than expose the 555’s eight pins: it sets you up to run your 555 timer in astable mode with slots to insert two resistors and a capacitor of your choice. This board eliminates all the wiring for the 555 timer. The 555 Timer Breakout Board Plus will cut out the tedium of setting up the 555 timer and will allow hobbyists to dig straight in to their projects.

As a electronics hobbyist myself, I recognize the usefulness of this simple device, but also acknowledge its relevance is limited to the niche market of hobbyist electronics. If you want this device or think a friend could use it, please contribute to the campaign and buy a 555 timer breakout board!

555 Timer Breakout Board Plus – [Link]

DIY automatic water timer


Kyle wrote an article detailing his DIY automatic water timer:

Now that I have power and output figured out, I need to work on the control aspect. 555 timers are great for simple applications requiring up to a few minutes of delay. At 10 minutes, the RC values needed would boarder the danger zone of the timer not functioning correctly due to the leakage current of the capacitor and the small charge current of the resistor. I could have cascaded two or more timers together but that would be sloppy so I fell back on my trusty friend – the ATtiny micro controller. This would allow me to make changes as I want without redesigning the board.


DIY automatic water timer – [Link]

Sound Activated Switch


Clap switch/Sound-activated switch designed around op-amp, flip-flop and popular 555 IC. Switch avoids false triggering by using 2-clap sound. Clapping sound is received by a microphone, the microphone changes the sound wave to electrical wave which is further amplified by op-amp.

555 timer IC acts as mono-stable multi-vibrator then flip-flop changes the state of output relay on every two-clap sound. This can be used to turn ON/OFF lights and fans. Circuit activates upon two-clap sound and stays activated until another sound triggers the circuit.

Sound Activated Switch – [Link]

Long Duration Timer


This timer project can be used to switch ON/OFF any device after a set time, this circuit can be used in lots of application like switched ON/OFF Radio, TV, Fan, Pump, kitchen timer, the circuit describe here its unique in its own.

Project has been designed around two CMOS IC CD4001 and CD4020. Two gates of CD4001 make the oscillator and rest has been configured as flip-flop, BC547 transistor is to drive the Relay. Circuit is pretty simple, has jumpers to set the required time duration, Preset is to set the 1Hz oscillator. SW1 is to start the timer, SW2 Power on/off project. Relay output switch contacts can handle 230V AC @ 5Amps

Long Duration Timer – [Link]