{"id":774,"date":"2022-12-08T05:53:12","date_gmt":"2022-12-08T04:53:12","guid":{"rendered":"http:\/\/lesmrdtrucs.mataf35400.fr\/?page_id=774"},"modified":"2022-12-08T05:57:02","modified_gmt":"2022-12-08T04:57:02","slug":"une-led-en-220v","status":"publish","type":"page","link":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/une-led-en-220v\/","title":{"rendered":"Une LED en 220V"},"content":{"rendered":"\t\t
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De par sa dur\u00e9e de vie tr\u00e8s longue, une LED permet de donner une identification de fonctionnement de fa\u00e7on bien commode. C\u2019est une des raisons qui font regretter qu\u2019elle soit limit\u00e9e par la faible tension qu\u2019elle supporte. Il y a bien s\u00fbr la possibilit\u00e9 de mettre une r\u00e9sistance \u00ab\u00a0solide\u00a0\u00bb en s\u00e9rie, mais cela entra\u00eene une perte de puissance \u00e9norme. Le but de la man\u0153uvre n’est pas de construire un radiateur.<\/span><\/p>

Les bricoleurs qui nous \u00e9crivent ont souvent exprim\u00e9 le d\u00e9sir de pouvoir utiliser une LED aussi souplement qu’une petite ampoule au n\u00e9on, une LED que l’on pourrait brancher sur le secteur en quelque sorte.<\/span><\/p>

Cela est possible \u00e0 l’aide d’un petit truc. Pour limiter le courant, on se sert de la caract\u00e9ristique de r\u00e9sistance au courant alternatif d’un condensateur (sa capacitance). Il n’y a pas de perte de puissance dans le condensateur, car le courant traversant le condensateur et la tension qui r\u00e8gne \u00e0 ses bornes sont d\u00e9phas\u00e9s de 90\u00b0 l’un par rapport \u00e0 l’autre. La dissipation de puissance est \u00e9gale \u00e0, formule dans laquelle \u03d5 est le d\u00e9phasage entre la tension u et le courant, sachant que le cosinus de 90\u00b0 est \u00e9gal \u00e0 z\u00e9ro, la puissance est nulle.<\/span><\/p>

Une diode zener est prise dans le circuit de fa\u00e7on \u00e0 ce que la LED ne soit pas d\u00e9truite par un courant de mise en fonction trop important. Au cours de la demi-p\u00e9riode n\u00e9gative, la diode zener D2 fonctionne comme une diode ordinaire en sens passant et elle permet d’\u00e9viter que la tension inverse ne devienne trop forte aux broches de la LED.<\/span><\/p>

Au passage brutal \u00e0 la demi-p\u00e9riode positive, D2 permet d’\u00e9viter que la tension aux bornes de la LED D1 et de la r\u00e9sistance R1 ne d\u00e9passe 2,7 volts. Si on se sert d’une diode ordinaire \u00e0 la place de cette diode zener (ce que nous faisions lors de notre montage initial), le risque de voir la diode partir en fum\u00e9e est certain.<\/span><\/p>

La valeur de C1 est fonction du courant d\u00e9sir\u00e9 au travers de la LED. Pour C1 = 100 n, ce courant atteint 4 mA. Si on prend C1 = 470 n, il atteindra pr\u00e8s de 20 mA.<\/span><\/p><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div><\/div>

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De par sa dur\u00e9e de vie tr\u00e8s longue, une LED permet de donner une identification de fonctionnement de fa\u00e7on bien commode. C\u2019est une des raisons qui font regretter qu\u2019elle soit limit\u00e9e par la faible tension qu\u2019elle supporte. Il y a bien s\u00fbr la possibilit\u00e9 de mettre une r\u00e9sistance \u00ab\u00a0solide\u00a0\u00bb en s\u00e9rie, mais cela entra\u00eene une […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"ocean_post_layout":"","ocean_both_sidebars_style":"","ocean_both_sidebars_content_width":0,"ocean_both_sidebars_sidebars_width":0,"ocean_sidebar":"0","ocean_second_sidebar":"0","ocean_disable_margins":"enable","ocean_add_body_class":"","ocean_shortcode_before_top_bar":"","ocean_shortcode_after_top_bar":"","ocean_shortcode_before_header":"","ocean_shortcode_after_header":"","ocean_has_shortcode":"","ocean_shortcode_after_title":"","ocean_shortcode_before_footer_widgets":"","ocean_shortcode_after_footer_widgets":"","ocean_shortcode_before_footer_bottom":"","ocean_shortcode_after_footer_bottom":"","ocean_display_top_bar":"default","ocean_display_header":"default","ocean_header_style":"","ocean_center_header_left_menu":"0","ocean_custom_header_template":"0","ocean_custom_logo":0,"ocean_custom_retina_logo":0,"ocean_custom_logo_max_width":0,"ocean_custom_logo_tablet_max_width":0,"ocean_custom_logo_mobile_max_width":0,"ocean_custom_logo_max_height":0,"ocean_custom_logo_tablet_max_height":0,"ocean_custom_logo_mobile_max_height":0,"ocean_header_custom_menu":"0","ocean_menu_typo_font_family":"0","ocean_menu_typo_font_subset":"","ocean_menu_typo_font_size":0,"ocean_menu_typo_font_size_tablet":0,"ocean_menu_typo_font_size_mobile":0,"ocean_menu_typo_font_size_unit":"px","ocean_menu_typo_font_weight":"","ocean_menu_typo_font_weight_tablet":"","ocean_menu_typo_font_weight_mobile":"","ocean_menu_typo_transform":"","ocean_menu_typo_transform_tablet":"","ocean_menu_typo_transform_mobile":"","ocean_menu_typo_line_height":0,"ocean_menu_typo_line_height_tablet":0,"ocean_menu_typo_line_height_mobile":0,"ocean_menu_typo_line_height_unit":"","ocean_menu_typo_spacing":0,"ocean_menu_typo_spacing_tablet":0,"ocean_menu_typo_spacing_mobile":0,"ocean_menu_typo_spacing_unit":"","ocean_menu_link_color":"","ocean_menu_link_color_hover":"","ocean_menu_link_color_active":"","ocean_menu_link_background":"","ocean_menu_link_hover_background":"","ocean_menu_link_active_background":"","ocean_menu_social_links_bg":"","ocean_menu_social_hover_links_bg":"","ocean_menu_social_links_color":"","ocean_menu_social_hover_links_color":"","ocean_disable_title":"default","ocean_disable_heading":"default","ocean_post_title":"","ocean_post_subheading":"","ocean_post_title_style":"","ocean_post_title_background_color":"","ocean_post_title_background":0,"ocean_post_title_bg_image_position":"","ocean_post_title_bg_image_attachment":"","ocean_post_title_bg_image_repeat":"","ocean_post_title_bg_image_size":"","ocean_post_title_height":0,"ocean_post_title_bg_overlay":0.5,"ocean_post_title_bg_overlay_color":"","ocean_disable_breadcrumbs":"default","ocean_breadcrumbs_color":"","ocean_breadcrumbs_separator_color":"","ocean_breadcrumbs_links_color":"","ocean_breadcrumbs_links_hover_color":"","ocean_display_footer_widgets":"default","ocean_display_footer_bottom":"default","ocean_custom_footer_template":"0","footnotes":""},"class_list":["post-774","page","type-page","status-publish","hentry","entry"],"_links":{"self":[{"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/pages\/774","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/comments?post=774"}],"version-history":[{"count":4,"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/pages\/774\/revisions"}],"predecessor-version":[{"id":783,"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/pages\/774\/revisions\/783"}],"wp:attachment":[{"href":"https:\/\/lesmrdtrucs.mataf35400.fr\/index.php\/wp-json\/wp\/v2\/media?parent=774"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}