![\"\"](\"https:\/\/www.andersknelson.com\/blog\/wp-content\/uploads\/2014\/03\/IMG_1205-1024x768.jpg\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/www.andersknelson.com\/blog\/wp-content\/uploads\/2014\/03\/IMG_1208-1024x768.jpg\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/www.andersknelson.com\/blog\/wp-content\/uploads\/2014\/03\/IMG_1209-1024x768.jpg\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/www.andersknelson.com\/blog\/wp-content\/uploads\/2014\/03\/IMG_1210-1024x768.jpg\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/www.andersknelson.com\/blog\/wp-content\/uploads\/2014\/03\/IMG_1207-1024x768.jpg\")
<\/figure>\n\n\n\n![\"\"](\"https:\/\/www.andersknelson.com\/blog\/wp-content\/uploads\/2014\/03\/IMG_1211-1024x768.jpg\")
<\/figure>\n<\/figure>\n\n\n\nWhat it does<\/h2>\n\n\n\n\n- Displays arbitrary text\/graphics in a variety of ways.<\/li>\n<\/ul>\n\n\n\n
What it’s made of<\/h2>\n\n\n\n\n- 74AHC595-series 8-bit shift registers<\/li>\n\n\n\n
- PFET transistors (to source current through columns)<\/li>\n\n\n\n
- NFET transistors (to sink current through rows)<\/li>\n\n\n\n
- LM3150 DC\/DC buck convertor<\/li>\n\n\n\n
- 10mm LEDs<\/a><\/li>\n\n\n\n
- A bunch of support components<\/li>\n\n\n\n
- Custom PCB<\/a> designed in EAGLE<\/a> and fabricated at PCBExpress<\/a><\/li>\n\n\n\n
- Firmware <\/a>written in C using MPLABX<\/a>, compiled by XC16<\/a> and loaded using an ICD3<\/a><\/li>\n<\/ul>\n\n\n\n
Theory of operation<\/h2>\n\n\n\n
Send it bunch of bits over SPI a zillion times a second and you get pretty text! The code linked to above just sets the stage – it’s up to you to send the display what you want to see. When I get some extra time (LOL) I’ll hook it up to a WiFi module and use it as a wall-clock.<\/p>\n\n\n\n
Conclusion<\/h2>\n\n\n\n
It works, yay! Lessons learned:<\/p>\n\n\n\n
\n- Light-bleed into adjacent LEDs is easily fixed with some opaque heat-shrink tubing.<\/li>\n\n\n\n
- Each row has a considerable amount of capacitance that needs to be discharged with each row switch. Write an all-off sequence to the column drivers to do this.<\/li>\n\n\n\n
- Light output is considerably reduced when you scan the display, essentially reducing it to 1\/7 (in this case using 7 rows) of the original brightness. You can overdrive the rows by 7x (in this case using 7 rows) to get around this but you must make sure your OE line is de-asserted until you start switching the rows or you’ll pop the LEDs.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
An oversized scanned-matrix display using 10mm LEDs. Background When Steven […]<\/p>\n","protected":false},"author":1,"featured_media":79,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[6],"class_list":["post-41","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-projects","tag-led"],"_links":{"self":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=41"}],"version-history":[{"count":14,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41\/revisions"}],"predecessor-version":[{"id":1128,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41\/revisions\/1128"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/media\/79"}],"wp:attachment":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
What it’s made of<\/h2>\n\n\n\n\n- 74AHC595-series 8-bit shift registers<\/li>\n\n\n\n
- PFET transistors (to source current through columns)<\/li>\n\n\n\n
- NFET transistors (to sink current through rows)<\/li>\n\n\n\n
- LM3150 DC\/DC buck convertor<\/li>\n\n\n\n
- 10mm LEDs<\/a><\/li>\n\n\n\n
- A bunch of support components<\/li>\n\n\n\n
- Custom PCB<\/a> designed in EAGLE<\/a> and fabricated at PCBExpress<\/a><\/li>\n\n\n\n
- Firmware <\/a>written in C using MPLABX<\/a>, compiled by XC16<\/a> and loaded using an ICD3<\/a><\/li>\n<\/ul>\n\n\n\n
Theory of operation<\/h2>\n\n\n\n
Send it bunch of bits over SPI a zillion times a second and you get pretty text! The code linked to above just sets the stage – it’s up to you to send the display what you want to see. When I get some extra time (LOL) I’ll hook it up to a WiFi module and use it as a wall-clock.<\/p>\n\n\n\n
Conclusion<\/h2>\n\n\n\n
It works, yay! Lessons learned:<\/p>\n\n\n\n
\n- Light-bleed into adjacent LEDs is easily fixed with some opaque heat-shrink tubing.<\/li>\n\n\n\n
- Each row has a considerable amount of capacitance that needs to be discharged with each row switch. Write an all-off sequence to the column drivers to do this.<\/li>\n\n\n\n
- Light output is considerably reduced when you scan the display, essentially reducing it to 1\/7 (in this case using 7 rows) of the original brightness. You can overdrive the rows by 7x (in this case using 7 rows) to get around this but you must make sure your OE line is de-asserted until you start switching the rows or you’ll pop the LEDs.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
An oversized scanned-matrix display using 10mm LEDs. Background When Steven […]<\/p>\n","protected":false},"author":1,"featured_media":79,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[6],"class_list":["post-41","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-projects","tag-led"],"_links":{"self":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=41"}],"version-history":[{"count":14,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41\/revisions"}],"predecessor-version":[{"id":1128,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41\/revisions\/1128"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/media\/79"}],"wp:attachment":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Theory of operation<\/h2>\n\n\n\n
Send it bunch of bits over SPI a zillion times a second and you get pretty text! The code linked to above just sets the stage – it’s up to you to send the display what you want to see. When I get some extra time (LOL) I’ll hook it up to a WiFi module and use it as a wall-clock.<\/p>\n\n\n\n
Conclusion<\/h2>\n\n\n\n
It works, yay! Lessons learned:<\/p>\n\n\n\n
- \n
- Light-bleed into adjacent LEDs is easily fixed with some opaque heat-shrink tubing.<\/li>\n\n\n\n
- Each row has a considerable amount of capacitance that needs to be discharged with each row switch. Write an all-off sequence to the column drivers to do this.<\/li>\n\n\n\n
- Light output is considerably reduced when you scan the display, essentially reducing it to 1\/7 (in this case using 7 rows) of the original brightness. You can overdrive the rows by 7x (in this case using 7 rows) to get around this but you must make sure your OE line is de-asserted until you start switching the rows or you’ll pop the LEDs.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
An oversized scanned-matrix display using 10mm LEDs. Background When Steven […]<\/p>\n","protected":false},"author":1,"featured_media":79,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[6],"class_list":["post-41","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-projects","tag-led"],"_links":{"self":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=41"}],"version-history":[{"count":14,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41\/revisions"}],"predecessor-version":[{"id":1128,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/41\/revisions\/1128"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=\/wp\/v2\/media\/79"}],"wp:attachment":[{"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.andersknelson.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}