[time-nuts] help

[albertson.chris at gmail.com]

You don't care about the lag in cron. You care about the variation of the lag.   

Then again. The main cause of lag in a fog horn is the speed of sound  

You set cron to fire at T minus the average lag time. 

> On May 2, 2016, at 2:36 PM, Nick Sayer via time-nuts <time-nuts at febo.com> wrote:
> 
> 
>> On May 2, 2016, at 9:51 AM, jimlux <jimlux at earthlink.net> wrote:
>> 
>> 
>> The real question is whether "cron" is timely enough.  No matter, just write a script (or python) that reads time in a loop (and you can put a sleep in there) and pulses the GPIO when needed.
> 
> A Raspberry Pi with nothing else on its plate will have a cron-to-shell script latency easily under 100 ms, possibly under 10.
> 
> If it were me and I were triggering a relay for some sort of external circuit, I’d probably be happy it was on the right side of 500 ms. If I cared more than that, then step 1 would be to do as others have suggested and come up with a microcontroller + GPS solution instead of NTP + cron. Ironically, that’d be around the same price (albeit more engineering work).
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