{"id":18080,"date":"2022-04-14T09:34:17","date_gmt":"2022-04-14T16:34:17","guid":{"rendered":"https:\/\/rustybolt.info\/wordpress\/?p=18080"},"modified":"2022-04-15T04:20:44","modified_gmt":"2022-04-15T11:20:44","slug":"2022-04-14","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=18080","title":{"rendered":"2022-04-14 Watson’s Buzz Beeper"},"content":{"rendered":"

Watson’s Buzz Beeper<\/p>\n

I built this Buzz Beeper to find out if an audible tone could be used for sending simple commands, like turn on. Recently I built a microphone preamp with a bandpass filter that can detect my whistle. But it can be triggered by loud noise. So how about I generate a tone modulated with an on-off square wave that would have to be detected to trigger the command. The unmodulated tone itself won’t trigger the command, giving some noise immunity.<\/p>\n

I connected a piezo beeper to 9 volts DC and I could hear the 4 kHz tone out the room’s door and down the hall. This tone could be used for sensing objects like ultrasonic transducers – I can hear the standing waves as I walk around. So I added an astable multivibrator to drive the piezo with a square wave (see schematic). This gives a “buzzing beep”, a 4 kHz tone that’s buzzing or humming on and off. I think one way of describing it is if you had a 4 kHz signal generator connected to an amplifier without a ground connected.<\/p>\n

This tone “carrier” can be received, filtered, detected and the square wave recovered. If it’s present for so many milliseconds it can be considered as a positive command to switch or toggle a circuit.<\/p>\n

Without the .01 uF across the piezo beeper, the astable multivibrator wouldn’t oscillate at its proper frequency; it was being triggered by the pulses from the piezo. The 0.01 uF capacitor helped a lot. But the piezo’s on and off is slower.<\/p>\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

Watson’s Buzz Beeper I built this Buzz Beeper to find out if an audible tone could be used for sending simple commands, like turn on. Recently I built a microphone preamp with a bandpass filter that can detect my whistle. But it can be triggered by loud noise. So how about I generate a tone <\/p>\n

(Read More…)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8,329,339,1267],"tags":[2114,2115],"class_list":["post-18080","post","type-post","status-publish","format-standard","hentry","category-audio","category-functional-blocks","category-generators-oscillators","category-sodium-ion","tag-buzz-beeper","tag-modulated-tone"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/18080","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=18080"}],"version-history":[{"count":6,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/18080\/revisions"}],"predecessor-version":[{"id":18089,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/18080\/revisions\/18089"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18080"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18080"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18080"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}