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Based on the idea from http://www.josepino.com/pic_projects/?timebase I have created a 1Hz Clock Generator. I use PIC12F675 as it’s available locally. Its price is just about US$1.
The concept is using 32.768kHz crystal as a clock for the PIC. Therefor, the internal instruction clock is 32768/4 = 8192 Hz. By using the 16 bit Timer1 to count the instruction clock cycles, the interrupt will occur every 8 second. This period can be reduced by setting initial value of the Timer1 (TMR1H:TMR1L).

1Hz Clock Generator using PIC12F675 - [Link]

Here is an interesting LED binary clock by instructables user ElevenOf9. I really like the single sided PCB, and the way the LEDs are arranged. It just looks cool! [via]

This is the second revision of my PIC based LED binary clock. The original version was the first PIC project I attempted, it used a PIC16F84A to do both the timekeeping and control the display matrix, unfortunately it didn’t keep good enough time and gained about a minute every week.

LED Binary Clock – [Link]

This clock is constucted using an old HDD. The clock is controlled using an ATMEGA128 microcontroller and the time is counted from DS1307 real time clock IC. Motor is controlled from TDA5140A using standard configuration. The device is also equipped with RS232 interface to load new software and a small universal remote.

HDDClock – Hard Drive Clock - [in polish] [Link] + [Youtube video]

A 12hr/24hr LED Clock with display control, uses a microcontroller PIC 16F84A or 16F628A and a few parts.

This LED clock may not be the easiest to build but surely it is the one with fewer parts that you can find, for that reason I call it “The ANP LED Clock”. (ANP stands for Almost No Parts.)

Here are the features on this ANP LED Clock:

• Can use common cathode or common anode 7-segment LED displays
• Displays time as 12 hours or 24 hours format.
• Allows to enable or disable the display for battery-operated circuits
• Can control the display brightness to reduce power consumption
• 7-segment LED displays are charlieplexed to reduce I/O ports usage
• PM LED indicator (optional)
• Only 10 parts needed: 1 PIC 16F84A,
• 22pF Capacitors, 2 n.o. switches, 1 4Mhz Xtal and 4 CA or CC 7segment LED displays
• Operates from 2.5 to 5.5 Volts, it can even work with a 3V coin battery

‘Almost No Parts’ 12/24hrs LED Clock - [Link]

A common challenge when working with embedded systems is keeping track of real time. Luckily, most microcontrollers have timers that can be used with a precision quartz crystal — already present for the CPU clock — to keep track of real time. In this video tutorial, we show how you can use the timer interrupts on an ATMega168 chip to make a simple timer. Building off of this, it is possible to make your own reasonably accurate alarm clock, create systems to perform timed automated tasks, or create a multitude of other projects.

Crystal Real Time Clock - [Link]

What do you do if you have a spare LCD module with backlight, a weird 16 button keyboard, and a PIC16F877A microcontroller gathering dust? A monster Martian Clock immediately springs to mind.

You are probably thinking “There are hundreds of PIC clocks on the Net – do we need yet another one?

This clock is quite different than all other PIC clocks I’ve seen in this that it has multiple timers that can work with different speeds (for example, you can have one showing your local time, another working on Mars day time, another showing the moon phase, etc.)

Mars Clock – PIC-microcontroller-based clock - [Link]

That’s a very compact nixie clock based on PIC16F84A and 74141 driver IC and MPSA92 high voltage transistors.

PIC16F84A Nixie Clock - [Link]

This project uses RGB LEDs to create a clock face. Each hand is assigned a colour and as the hands overlap on the face of the clock it mixes the colours.

The clock uses a single AA battery to power the display which is boosted to 5 volts with a switching mode power supply. The power supply should be able to use any AA battery that is at 0.7 volts or higher, which means that it should still work fine with AA batteries that may be “dead” when used in other devices.

The heart of the clock is a DS1307 realtime clock with a CR2032 coin cell battery backup. The battery should be sufficient to keep the time for at least a couple of years.

LED Desktop Clock - [Link]

Almost all commercially available GPS OEM modules provide a 1pps output, synchronized with GPS time. This pulse could be used as a reference to generate accurate high-frequency clocks, but special design has to address the short-term jitter affecting the 1pps signal. As a general guideline, an oven-stabilized crystal oscillator who guarantees the short-term stability is synchronized with the GPS 1pps for the long-term accuracy.

GPS-based universal clock generator – [Link]

The Nixie Clock uses the Make Controller’s Ethernet capabilities to go online and check what the time is, via a protocol called NTP (Network Time Protocol). Once it determines the current time, it uses the digital outs on the Make Controller to communicate with a pair of custom circuit boards that drives the nixies and updates the time. [via]

Nixie Clock – [Link]