Arduino LED clock with half hour accuracy

Some people like to know exact time (hours, minutes and event seconds) while other are satisfied with “around” time. So this project might be just right. It is fairly easy to build since there are only twelve single color LEDs used. NextLab did their job to the end – instead of leaving circuit open, they laser cut nice acrylic enclosure that makes this clock stand out. Clock is powered by Arduino Nano. Even if displayed time accuracy is half an hour, internal time is kept precisely with external RTC DS1307 chip. The motivation of this is that platform can be used for future projects where someone might want to build accurate display like using RGB LEDs or different methods. Continue reading

Adjusting RTC accuracy with Arduino

Real time clocks like DS3232 is already quite accurate. By default is is specified to be 2.5ppm accurate between temperatures 0ºC and 40ºC. This number means an 80 seconds error during one year. We all know that aging of electronics, temperature and other factors may influence the accuracy. So DS3232 has internal 8-bit aging offset register where clock adjustment can be programmed about ±13ppm. Kerry set up a simple prototype board where he connected Arduino to RTC chip and wrote small function which access aging offset register and changes its value with new one. Then he was able to measure frequency change with HP5350B microwave counter. He found out that each adjustment step changes clock frequency by 0.1ppm meaning 0.002 to 0.003Hz. Keep in mind that adjustment values stays as long as chip is powered with backup battery. Continue reading

Handy way of configuring RTC modules

If you are planning to include RTC in to your project, probably the best way is to use ready made modules that come with RTC IC, crystal and backup battery. In fact these modules once powered do work stand alone. IT is like a small clock that can be connected anywhere. One thing may be tricky – setting correct time and other configurations. The only way is to connect to it using I2C or SPI interface. To make things easier, Luca brought special tools for this. He made a GUI for PC and Arduino sketch. All you need to upload Arduion sketch and connect to PC. Then run PC program. After all is set-up, you can attach RTC module to Arduino using I2C interface and start configuring it. Practically Arduino accepts simple commands through serial interface. So any terminal software would work too. But GUI makes things much simpler and faster. Here you can set time and date by picking right values and uploading to Arduino. Once set-up is done, you can disconnect RTC module and use elsewhere. Continue reading

Automatic light controller looks at sunset time

If you use standard automatic light controller then you know that it is mechanical clock based switch or electronic with ambient light detector. Mechanical one require regular time adjusting since sunset time variates during year. Second one would be OK – it senses darkness with LDR and then turns on the lights. But things happen, LDR may get covered with objects or simply dark clouds my trigger the lights. Anyway there is another solution – smart clock that keeps track of sunset times. Paulo decided to build lighting timer using sunset and sunrise time calculating algorithm. So lights are turned on time no matter what season is currently on. Additionally Arduino based devices is equipped with 7 segment display, couple push buttons for setting time, battery backed RTC. Lights are turned on by using mechanical relay. Continue reading

Arduino and 1-wire RTC

Real time chips are common where time count is needed. You can find different version of RTC’s that have different features and have different interface to connect to. In this project a 1-wire RTC DS1904 is used. The easy part of using this interface that it require only one wire for transferring data and powering device itself. Of course it has to be Grounded in order to work. So generally its two wires. DS1904 comes as iButton. RTC is identified with 64-bit factory lasered ROM that makes everyone unique when detected. As real time clock it features a calendar, time, stopwatch, hour meter, interval -o-meter. With Arduino is easy as there is a library for 1-wire. Share your thoughts why iButton shape for RTC can benefit in reality… Continue reading

Christmas countdown clock

This might be fun project to do with kids. After several kit attacks with questions like “How long until Christmas?” Dr. Ayars decided to put a Christmas timer countdown project where you can clearly see how long there is left to wait until presents arrive. Counter is made of several common parts with Arduino Pro Mini in the middle. In order to count precisely there is a Real Time Clock (RTC) DS3231 used. And of course timing is displayed on standard 2×16 LCD. It shows days, hours, minutes and seconds left until upcoming Christmas. So be sure to set timer correctly and let the waiting begin. It’s about time, isn’t it? Continue reading