According to General Relativity, we all experience finite amount of time dilation in our daily lives, depending upon our location, elevation, and velocity. At the speeds we travel at and the elevation we experience in everyday, time dilation is so small that it’s not detectable to us. But the high accuracy of atomic clocks have provided evidence for this effect even at our everyday speed. Cameron Meredith has shared an interesting project on Hackaday.io about using a rubidium atomic frequency standard to continuously track local time dilation effects relative to a reference GPS clock.
Rubidium standard RTC
This project uses a rubidium atomic frequency standard to continuously track local time dilation effects relative to GPS, and eventually the WWVB US atomic clock radio frequency signal. The idea is to continuously monitor and record the cumulative time deviation. An I2C multiplexer board allows for more than one RTC module (Since these have a hard coded I2C address you can normally only use one). I went for three – One tracking GPS time, another tracking the rubidium standard, and the last one as a control or reference clock – without compensation.
This PIC18F25K20-based clock uses radio receivers to synchronize the time with that from the GPS satellites or the DCF77 transmitter, both of which are referenced to atomic clocks.
Very accurate clock referenced to an atomic clock
This project is a clock with radio receivers which can receive the exact date and time from the DCF77 time signal transmitter or the UTC from the GPS satellites and display it on a 128×64 pixel graphic display. DCF77 transmitter and GPS is synchronized to an atomic clock. So basically this project can “connect to” an atomic clock.
This project is an open design: open hardware and open source software.
Brett’s new masterclock is Arduino-controlled and keeps very accurate time by periodically synchronizing with the DCF77 “Atomic” Clock in Mainflingen near Frankfurt, Germany. The DCF77 library for Arduino is used to decode the time signal broadcasted from the atomic clock. The time is displayed as hours, minutes, and seconds on six 1″ seven segment LEDs. A 4×20 I2C LCD display is also used in the project to display additional info such as display brightness, sync information, signal quality, auto tune’d frequency, auto tuned quartz accuracy, etc. Both the displays are auto-dimmed based on the surrounding light intensity using an LDR sensor and pulse width modulation technique. His clock also includes a bluetooth link for updating the Arduino firmware from a PC without an USB cable.
Accurate master clock synchronized with the DCF77 atomic clock