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Maker Jon Mackey, sick of poor protection and thus inaccurate “atomic” wall clocks, has penned a information to turning an STMicroelectronics STM32 microcontroller right into a homebrew time sign radio station designed to fill gaps in NIST’s WWVB protection — with correct timing supplied by a GPS module.
“I reside in northern New Hampshire, and in response to the NIST protection map, I ought to be capable to reliably obtain the WWVB sign at evening,” Mackey explains, referring to a radio station which transmits atomic-clock-derived time indicators to acceptable receiving gadgets together with wall clocks and wristwatches. “I personal a number of WWVB ‘Atomic’ clocks. Typically these clocks work fairly effectively, however for greater than two weeks in December 2023 my clocks weren’t updating.”
Having discovered present tasks which create a WWVB-compatible time sign with a Microchip ATtiny microcontroller, Mackey set about designing his personal utilizing an STMicro STM32 — particularly the WeAct Studio STM32F103CBT6 BluePill+ module. For the time supply itself, Mackey turned to a u-blox NEO-6M GPS receiver, the time data from which is broadcast from the microcontroller to close by appropriate radio receivers.
A microcontroller and GPS module is sufficient to simulate time transmissions from NIST’s WWVB station — to a four-inch vary, anyway. (📷: Jon Mackey)
“On startup, and on the half hour, the WWVB simulator’s time is up to date from the serial stream coming from the GPS module,” Mackey explains of the simulator’s operation. “One of many STM32’s timers outputs a ~60kHz 50% responsibility cycle PWM [Pulse Width Modulation] sign that serves because the AM [Amplitude Modulation] service, the sign that drives the antenna. The antenna radiates, at most, about 10cm [around 4 inches]. It is extremely weak, however that is OK.
“On each even minute, a brand new 60 byte construction is initialized that represents the present time as outlined by the NIST. Every byte on this construction represents one little bit of transmitted information. The bit is usually a 0, 1, or a marker. It takes one second to transmit one bit. The size of time that the AM service is current determines whether or not the bit is a 0, 1, or a marker. Markers are utilized by the clock to know when a brand new 60 second block of knowledge is beginning and to validate the information acquired.”
The complete mission write-up, together with a elements record and supply code, is out there on Mackey’s Instructables web page.
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