{"id":255,"date":"2020-07-20T22:43:05","date_gmt":"2020-07-21T05:43:05","guid":{"rendered":"https:\/\/boom-tracker.com\/tracker\/?p=255"},"modified":"2020-07-20T22:43:07","modified_gmt":"2020-07-21T05:43:07","slug":"and-now-for-the-time-and-temperature","status":"publish","type":"post","link":"https:\/\/boom-tracker.com\/tracker\/blog\/and-now-for-the-time-and-temperature\/","title":{"rendered":"And now for the time and temperature…"},"content":{"rendered":"\n

I’ve been noticing that the microphone that has the DHT-11 temperature sensor consistently under-performs the other microphone in terms of how well is stays in sync with the NTP server. I have documented previously<\/a> that trying to read a non-existent sensor caused major sync issues, but I now know that even if the sensor is working properly, it still throws the sync off slightly.<\/p>\n\n\n\n

On mic 001 (the one with the temperature sensor). I was seeing the average offset being somewhere around +\/-1300 microseconds, whereas on mic 004 (the one without the sensor or code to read it). I was typically seeing offsets of +\/-300-400 microseconds (1\/4 to 1\/3 as large). So I disabled the DHT-11 on mic 001, and within 15 minutes the average offset was +\/- 400-500 microseconds, and the timing of received sound waves was much more in sync. <\/p>\n\n\n\n

\"\"
I have no idea what this was, but both mics agree when it was.<\/figcaption><\/figure>\n\n\n\n

And zooming in on that first big positive peak you can see that they’re only about 400 microseconds apart, which is pretty good.<\/p>\n\n\n\n

\"\"
.9093730-.909344 = .000386 seconds, or 386 microseconds difference<\/figcaption><\/figure>\n\n\n\n

It’s not the 100 to 200 microsecond offset I’m looking for, but I can live with this level of error. <\/p>\n\n\n\n

Now what am I going to do with the temperature sensor? I still need to be able to measure ambient air temperature to calculate the speed of sound accurately, but it was never a requirement that I have 4 of them or that they be co-located with microphones. I have some spare ESP8266 feathers now, and while they’re not good for the microphones, I can easily re-purpose them to being a couple of temperature sensors. I’ll play with low-power deep-sleep and have them wake up every 30 seconds or so to check the temp and report in. That should give me a fairly accurate and current air temp. <\/p>\n","protected":false},"excerpt":{"rendered":"

I’ve been noticing that the microphone that has the DHT-11 temperature sensor consistently under-performs the other microphone in terms of how well is stays in sync with the NTP server. I have documented previously that trying to read a non-existent sensor caused major sync issues, but I now know that even if the sensor is… Continue reading And now for the time and temperature…<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"bgseo_title":"","bgseo_description":"","bgseo_robots_index":"index","bgseo_robots_follow":"follow","footnotes":""},"categories":[3,9,8],"tags":[],"class_list":["post-255","post","type-post","status-publish","format-standard","hentry","category-blog","category-experimentation","category-implementation"],"_links":{"self":[{"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/posts\/255","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/comments?post=255"}],"version-history":[{"count":1,"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/posts\/255\/revisions"}],"predecessor-version":[{"id":258,"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/posts\/255\/revisions\/258"}],"wp:attachment":[{"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/media?parent=255"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/categories?post=255"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/boom-tracker.com\/tracker\/wp-json\/wp\/v2\/tags?post=255"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}