{"id":90296,"date":"2022-04-05T08:00:08","date_gmt":"2022-04-05T06:00:08","guid":{"rendered":"https:\/\/botland.com.pl\/blog\/sygnal-pwm-czym-jest\/"},"modified":"2024-09-23T15:56:11","modified_gmt":"2024-09-23T13:56:11","slug":"co-je-to-signal-pwm","status":"publish","type":"post","link":"https:\/\/botland.cz\/blog\/co-je-to-signal-pwm\/","title":{"rendered":"Co je to sign\u00e1l PWM?"},"content":{"rendered":"\u010cas \u010dten\u00ed:<\/span> 3<\/span> min.<\/span><\/span>\t\t
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Co je to PWM a jak ji lze \u010d\u00edst?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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PWM je zkratka pro pulzn\u011b \u0161\u00ed\u0159kovou modulaci. Nejedn\u00e1 se o nic jin\u00e9ho ne\u017e o metodu \u0159\u00edzen\u00ed elektronick\u00fdch obvod\u016f pomoc\u00ed manipulace se samotn\u00fdm \u0159\u00eddic\u00edm sign\u00e1lem,<\/b> p\u0159esn\u011bji \u0159e\u010deno s jeho technick\u00fdmi parametry. To je d\u00e1no fyzik\u00e1ln\u00edmi vlastnostmi samotn\u00e9ho sign\u00e1lu PWM, kter\u00fd se skl\u00e1d\u00e1 z ji\u017e zm\u00edn\u011bn\u00fdch impulz\u016f. Jejich z\u00e1kladn\u00ed parametry se t\u00fdkaj\u00ed doby, po kterou z\u016fst\u00e1vaj\u00ed ve vysok\u00e9m stavu<\/b> (logick\u00e1 hodnota impulzu) <\/span>1) <\/span>a sp\u00ednac\u00ed frekvence sign\u00e1lu<\/b> PWM. Co to p\u0159esn\u011b znamen\u00e1? <\/span><\/p>\n

\u0160\u00ed\u0159ka je pom\u011br doby, po kterou byl elektrick\u00fd n\u00e1boj dod\u00e1v\u00e1n do p\u0159ipojen\u00e9ho p\u0159ij\u00edma\u010de b\u011bhem jednoho impulsu PWM<\/b>. Nap\u0159\u00edklad pokud m\u011b\u0159en\u00ed sign\u00e1lu PWM ukazuje frekvenci 300 Hz, doba jednotliv\u00e9ho pln\u00e9ho impulsu by byla 1\/300 sekundy [3,(3) milisekundy]. Podobn\u011b lze vypo\u010d\u00edtat i dobu, po kterou bude na jeden puls PWM p\u016fsobit proud – sta\u010d\u00ed vyn\u00e1sobit d\u0159\u00edve z\u00edskan\u00fd v\u00fdsledek n\u00e1pln\u00ed.<\/span><\/p>\n

Jak se tedy m\u011b\u0159\u00ed sign\u00e1l PWM? Nejjednodu\u0161\u0161\u00ed zp\u016fsob, jak to ud\u011blat, je prozkoumat jej laboratorn\u00edm osciloskopem<\/a><\/b>. Pak z\u00edsk\u00e1te i jeho p\u0159\u00edmou grafickou interpretaci. <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Proud bude dan\u00fdm obvodem prot\u00e9kat v d\u00e1vk\u00e1ch a \u0161\u00ed\u0159ka ka\u017ed\u00e9ho impulsu bude ur\u010dena faktorem napln\u011bn\u00ed<\/b>, kter\u00fd zn\u00e1zor\u0148uje dobu, za kterou bylo do p\u0159ij\u00edma\u010de p\u0159ivedeno nap\u00e1jen\u00ed. \u010c\u00edm \u0161ir\u0161\u00ed jsou jednotliv\u00e9 “kopce”, t\u00edm d\u00e9le bude v\u00fdkon aplikov\u00e1n. <\/p>\n

Na druhou stranu, pokud m\u011b\u0159en\u00ed sign\u00e1lu PWM na laboratorn\u00edm osciloskopu ukazuje spojitou \u010d\u00e1ru (za p\u0159edpokladu hodnoty v\u011bt\u0161\u00ed ne\u017e 0), znamen\u00e1 to, \u017ee do p\u0159ipojen\u00e9 z\u00e1t\u011b\u017ee te\u010de spojit\u00fd proud, a proto bude \u010dinitel pln\u011bn\u00ed 100 %.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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P\u0159\u00edklad sign\u00e1lu PWM s \u010dinitelem st\u0159\u00eddy 50 %<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Kde se PWM uplat\u0148uje?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Sign\u00e1ly PWM se pou\u017e\u00edvaj\u00ed mimo jin\u00e9 ve sp\u00ednan\u00fdch nap\u00e1jec\u00edch zdroj\u00edch,<\/a><\/b> kter\u00e9 jsou schopny \u0159\u00eddit za\u0159\u00edzen\u00ed, je\u017e jsou k nim p\u0159ipojena. Nej\u010dast\u011bji je v\u0161ak tento typ sign\u00e1lu zodpov\u011bdn\u00fd za p\u0159esnou regulaci ot\u00e1\u010dek elektromotoru<\/b>, i kdy\u017e m\u016f\u017ee fungovat tak\u00e9 jako regul\u00e1tor osv\u011btlen\u00ed<\/b>. Pou\u017eit\u00edm sign\u00e1lu PWM s n\u00edzk\u00fdm \u010dinitelem pln\u011bn\u00ed pro \u0159\u00edzen\u00ed z\u00edsk\u00e1me zpomalovac\u00ed efekt pro motor nebo stm\u00edvac\u00ed efekt pro sv\u011bteln\u00e9 zdroje. Zv\u00fd\u0161en\u00edm jeho hodnoty se motor ot\u00e1\u010d\u00ed rychleji a LED dioda vyza\u0159uje v\u00edce sv\u011btla. <\/p>\n

Stejn\u011b \u010dasto se PWM impuls pou\u017e\u00edv\u00e1 u ventil\u00e1tor\u016f<\/a><\/b>. To umo\u017e\u0148uje regulovat pr\u016ftok vzduchu, kter\u00fd je jimi \u010derp\u00e1n, a z\u00e1rove\u0148 minimalizovat hluk, kter\u00fd jednotliv\u00e9 lopatky ventil\u00e1toru vyd\u00e1vaj\u00ed. <\/p>\n

S PWM se setk\u00e1te tak\u00e9 v pulzn\u00edch zesilova\u010d\u00edch<\/b> a v \u0159\u00eddic\u00edch obvodech, jejich\u017e hlavn\u00edm \u00fakolem je \u0159\u00eddit provoz servomotor\u016f<\/b>. Proto je p\u0159esn\u00e9 m\u011b\u0159en\u00ed sign\u00e1lu PWM tak d\u016fle\u017eit\u00e9 v projektech zalo\u017een\u00fdch na mikropo\u010d\u00edta\u010d\u00edch z rodiny Arduino<\/a> a Raspberry Pi<\/a>. <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Jak se pou\u017e\u00edv\u00e1 modulace sign\u00e1lu PWM?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Ji\u017e v\u00edte, kde se pou\u017e\u00edv\u00e1 sign\u00e1l PWM. Ale co to v\u0161echno znamen\u00e1 v praxi? T\u00fdk\u00e1 se to nejr\u016fzn\u011bj\u0161\u00edch za\u0159\u00edzen\u00ed odeb\u00edraj\u00edc\u00edch proud, jako jsou elektromotory, \u017e\u00e1rovky, LED diody a mimo jin\u00e9 tak\u00e9 servomotory. V\u0161echna tato za\u0159\u00edzen\u00ed lze \u0159\u00eddit pomoc\u00ed jevu \u0161\u00ed\u0159kov\u011b pulzn\u00ed modulace<\/b>. <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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\n\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tPOD\u00cdVEJTE SE NA<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t
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<\/p>\n

Sign\u00e1l PWM je proto z\u00e1kladem mnoha projekt\u016f zalo\u017een\u00fdch na v\u00fdvojov\u00fdch desk\u00e1ch z rodiny Arduino. S t\u00edmto typem minipo\u010d\u00edta\u010de je mo\u017en\u00e9 nejen m\u011b\u0159it samotn\u00fd sign\u00e1l PWM, ale tak\u00e9 jej prakticky libovoln\u011b generovat . Sta\u010d\u00ed k tomu pou\u017e\u00edt funkce “pwmCounter” a “pwmValue”,  naps\u00e1t relativn\u011b jednoduch\u00fd k\u00f3d ,<\/b>jeho\u017e \u00fa\u010delem je spravovat extern\u00ed moduly a za\u0159\u00edzen\u00ed p\u0159ipojen\u00e1 k syst\u00e9mu. Minipo\u010d\u00edta\u010d Arduino<\/a>. Zjednodu\u0161en\u011b \u0159e\u010deno,  ur\u010dit\u00fd v\u00fdstupn\u00ed pin desky bude st\u0159\u00eddav\u011b p\u0159iv\u00e1d\u011bt a odpojovat nap\u011bt\u00ed v p\u0159esn\u011b definovan\u00e9m mal\u00e9m \u010dasov\u00e9m intervalu<\/b>. V praxi to znamen\u00e1, \u017ee pr\u016fm\u011brn\u00e1 hodnota nap\u011bt\u00ed na dan\u00e9m pinu bude klesat v z\u00e1vislosti na parametrech pou\u017eit\u00e9ho PWM sign\u00e1lu.  <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Jak se tedy sign\u00e1l PWM pou\u017e\u00edv\u00e1 v praxi? <\/span>Lze jej snadno pou\u017e\u00edt k nastaven\u00ed jasu LED diody.<\/b> kter\u00fd se pou\u017e\u00edv\u00e1 nap\u0159\u00edklad k osv\u011btlen\u00ed okol\u00ed v z\u00e1b\u011bru kamery p\u0159ipojen\u00e9 k mikropo\u010d\u00edta\u010di. <\/span>V tomto p\u0159\u00edpad\u011b je v\u0161ak d\u016fle\u017eit\u00e9 zajistit, aby se frekvence generovan\u00e9ho sign\u00e1lu PWM shodovala s parametrem clony kamery – jinak bude obraz vystaven charakteristick\u00fdm artefakt\u016fm zhor\u0161uj\u00edc\u00edm kvalitu zaznamenan\u00e9ho filmu.<\/span><\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Sign\u00e1l PWM – \u010casto kladen\u00e9 ot\u00e1zky<\/h2>\n\n
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