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]
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]
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]
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]
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]
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]
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]
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.
Simple timer with PIC16F628A - [Link]
This Photodiode based Alarm can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered. The circuit uses a PN Photodiode in the reverse bias mode to detect light intensity. In the presence of Laser / IR rays, the Photodiode conducts and provides base bias to T1.
The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential. IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable operates only when its reset pin becomes high. When the Laser / IR beam breaks, current through the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated.
A simple IR transmitter circuit is given which uses Continuous IR rays. The transmitter can emit IR rays up to 5 meters if the IR LEDs are enclosed in black tubes.
555 Photodiode alarm - [Link]
Raj @ embedded-lab.com build a programmable digital timer. He writes:
Digital timer switches are used to control the operation of electrical devices based on a programmed schedule. This project describes a programmable digital timer based on the PIC16F628A microcontroller that can be programmed to schedule the on and off operation of an electrical appliance. The appliance is controlled through a relay switch. This timer switch allows you to set both on and off time. That means, you can program when do you want to turn the device on and for how long you want it to be remained on. The maximum time interval that you can set for on and off operation is 99 hours and 59 minutes. The project provides an interactive user interface using a 16×2 character LCD along with 4 push buttons.
Programmable digital timer switch using a PIC Microcontroller - [Link]