Mjerač - komparator svijetla

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SRC="Symb075c00b700f0ff000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Mjerač - komparator svijetla</B></div> <div> <A HREF="vco_sa_555.htm" TARGET="_top" TITLE="Jednostavni VCO"><U><B><IMG BORDER="0" SRC="Symb075c00b700f0ff000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Jednostavni VCO</B></U></A></div> <div> <A HREF="rs232_opto_interface.htm" TARGET="_top" TITLE="Opto RS232 9600bps"><U><B><IMG BORDER="0" SRC="Symb075c00b700f0ff000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Opto RS232 9600bps</B></U></A></div> <div> <A HREF="3_3v_spi_interface.htm" TARGET="_top" TITLE="Interface 5V CPU na 3.3V SPI memoriju"><U><B><IMG BORDER="0" SRC="Symb075c00b700f0ff000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Interface 5V CPU na 3.3V SPI memoriju</B></U></A></div> <div> <A HREF="lcd_dvm_napajanje.htm" TARGET="_top" TITLE="Izolirano napajanje za LCD DVM"><U><B><IMG BORDER="0" SRC="Symb075c00b700f0ff000000.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Izolirano napajanje za LCD DVM</B></U></A></div> <bR> </td> <td valign="top" height=400 BGCOLOR="#FFFFFF" TEXT="#080000"> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-2650537455752702" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-2650537455752702" data-ad-slot="7117608876" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> <bR> <bR> <div> <B><IMG SRC="54bc6850.gif" border=0 width="454" height="389" ALT="Logaritamski mjerač svjetlosti" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div>      Ovdje je prikazan jednostavan logaritamski mjerač svijetla. Odlikuje ga jednostavnost, niska cijena, poboljšana temperaturna stabilnost. Trimerom se podešava izlazni nivo za potpuni mrak (cca 1V). Za minimalnu temperaturnu ovisnost kod određenog osvjetljenja potrebno je trimerom offseta podesiti da tada izlaz daje 2,5V. Po potrebi se trimer može zamijeniti i sa trimerom manje vrijednosti.</div> <bR> <div>      Dobiveni izlazni napon se zatim može analogno obrađivati te se lako može dobiti pasivni detektor pokreta koji detektira promjenu na primljenom svijetlu. Uslov je da postoji neko osvjetljenje prostora. Prelazak sjene preko detektora se može lako opaziti u cijeloj dinamici osvjetljenja jer sklop vrši logaritmiranje izmjerenog intenziteta te relativna promjena intenziteta svjetla daje uvijek isti amplitudni skok. Sa otpornikom 1M se podešava pojačanje promjene svjetla, a sa 10K se podešava potrebna amplituda za aktiviranje izlaza (1K..1M)</div> <bR> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-2650537455752702" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-2650537455752702" data-ad-slot="7117608876" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> <bR> <div> <IMG SRC="54ce99b0.gif" border=0 width="489" height="411" ALT="Detektor pokreta zbog nagle promjene osvjetljenja" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div>      Ako se izlazni napon osnovnog sklopa direktno spojiti na dva preostala invertora CD4069, tada će kod svijetlosti veće od podešene promijeniti logičko stanje svog izlaza u high (tj. možemo dobiti jeftini komparator svijetla - shema dolje). Prednost sheme je nekorištenje skupljih rail to rail operacionih pojačala (koji rješavaju problemi u dinamici ulaznog i izlaznog signala kada oni dosežu napone napajanja) te u širokoj dinamici podešavanja te relativno istoj osjetljivosti podešavanja prilikom bilo kojeg osvjetljenja. Otpornik 2M2 određuje histerezu komparatora. Bez njega komparator nema histerezu.</div> <bR> <div> <IMG SRC="54df48f0.gif" border=0 width="500" height="399" ALT="Logaritamski komparator osvjetljenja" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </td> </tr></table></body>