{"id":2645,"date":"2025-11-25T16:58:55","date_gmt":"2025-11-25T15:58:55","guid":{"rendered":"https:\/\/www.sciencetronics.com\/greenphotons\/?p=2645"},"modified":"2025-11-25T17:15:00","modified_gmt":"2025-11-25T16:15:00","slug":"demystifying-a-5x4-keypad-matrix-hc-35","status":"publish","type":"post","link":"https:\/\/www.sciencetronics.com\/greenphotons\/?p=2645","title":{"rendered":"Demystifying a 5&#215;4 keypad matrix HC-35"},"content":{"rendered":"\n<p>On your favorite selling sites for cheap electronics you may find a nice looking keypad\/push button matrix with 16 black buttons arranged in a 4&#215;4 matrix, another row of 4 red buttons and a row of eight 3mm red LEDs.<\/p>\n<p>But how is everything connected internally to the three pinheaders on the board (5&#215;2 pins, 3&#215;2 pins and 5&#215;2 pins)?<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-1.png\"><img loading=\"lazy\" decoding=\"async\" width=\"383\" height=\"443\" src=\"https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-1.png\" alt=\"\" class=\"wp-image-2647\" srcset=\"https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-1.png 383w, https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-1-259x300.png 259w\" sizes=\"auto, (max-width: 383px) 100vw, 383px\" \/><\/a><\/figure><\/div>\n\n\n<p>Since there was a big lack of information on all the sellers&#8217; sites, and even a search did not bring up clear information I beeped through all the wires and here is the internal circuit diagram. It&#8217;s a mix of a multiplexed matrix, direct push buttons with applied 10 k\u03a9 pull-up resistors and the LEDs in a common-anode (CA) configuration with 1 k\u03a9 resistors.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><a href=\"https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-2.png\"><img loading=\"lazy\" decoding=\"async\" width=\"917\" height=\"863\" src=\"https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-2.png\" alt=\"\" class=\"wp-image-2648\" style=\"width:471px;height:auto\" srcset=\"https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-2.png 917w, https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-2-300x282.png 300w, https:\/\/www.sciencetronics.com\/greenphotons\/wp-content\/uploads\/2025\/11\/image-2-768x723.png 768w\" sizes=\"auto, (max-width: 917px) 100vw, 917px\" \/><\/a><\/figure><\/div>\n\n","protected":false},"excerpt":{"rendered":"<p>On your favorite selling sites for cheap electronics you may find a nice looking keypad\/push button matrix with 16 black buttons arranged in a 4&#215;4 matrix, another row of 4 red buttons and a row of eight 3mm red LEDs. But how is everything connected internally to the three pinheaders on the board (5&#215;2 pins, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"enabled":false},"version":2}},"categories":[11,8,40],"tags":[58,56,59,44,64,60],"class_list":["post-2645","post","type-post","status-publish","format-standard","hentry","category-electronics_en","category-everything_en","category-leds","tag-arduino","tag-electronics","tag-keypad","tag-led","tag-microcontroller","tag-push-button-matrix","entry"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p48grL-GF","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/posts\/2645","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2645"}],"version-history":[{"count":3,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/posts\/2645\/revisions"}],"predecessor-version":[{"id":2651,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/posts\/2645\/revisions\/2651"}],"wp:attachment":[{"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2645"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2645"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2645"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}