{"id":18027,"date":"2022-04-07T13:13:38","date_gmt":"2022-04-07T20:13:38","guid":{"rendered":"https:\/\/rustybolt.info\/wordpress\/?p=18027"},"modified":"2022-04-07T13:16:16","modified_gmt":"2022-04-07T20:16:16","slug":"2022-04-07-audible-light-meter","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=18027","title":{"rendered":"2022-04-07 Audible Light Meter"},"content":{"rendered":"

This circuit could be used for blind to sense light. It’s a similar circuit to the police siren.<\/p>\n

The two transistors have a current gain of 200 X 200 or 40,000 so even a very tiny Q1 base current – microamps – causes a very large Q2 collector current. So a very small amount of light will cause this circuit to oscillate at a high pitch. Some resistance needs to be in series with the photocell, maybe 1k or more? It helps that the supply voltage is only 1.5 Volts. Still, I think it should have a 22 ohm resistor in series with the speaker. I had this circuit that was running from a 9V battery, and it tore the voice coil wires loose and the speaker went open – cheap radio scrap speaker!<\/p>\n

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

This circuit could be used for blind to sense light. It’s a similar circuit to the police siren. The two transistors have a current gain of 200 X 200 or 40,000 so even a very tiny Q1 base current – microamps – causes a very large Q2 collector current. So a very small amount of <\/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":[8,339,17,147],"tags":[2086,2085,62],"class_list":["post-18027","post","type-post","status-publish","format-standard","hentry","category-audio","category-generators-oscillators","category-meters-and-test-equipment","category-optics-and-light","tag-2-transistors","tag-audible-light-meter","tag-cds-photocell"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/18027","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=18027"}],"version-history":[{"count":1,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/18027\/revisions"}],"predecessor-version":[{"id":18028,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/18027\/revisions\/18028"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18027"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18027"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18027"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}