{"id":253,"date":"2010-03-04T21:53:38","date_gmt":"2010-03-04T20:53:38","guid":{"rendered":"http:\/\/www.sciencetronics.com\/greenphotons\/?p=253"},"modified":"2025-06-16T18:38:30","modified_gmt":"2025-06-16T16:38:30","slug":"lights-for-energihuset","status":"publish","type":"post","link":"https:\/\/www.sciencetronics.com\/greenphotons\/?p=253","title":{"rendered":"Lights for Energihuset"},"content":{"rendered":"

Today I designed a solar-cell powered LED lighting for a model of the planned energy education centre Energihuset<\/a> in Uppsala. The model was built by Nyr\u00e9ns Arkitektkontor<\/a> and equipped with 108 white light-emitting diodes, series connected in groups of three for a common supply voltage of 12 V. The model will be presented at the Swedish Energiting<\/a> in Stockholm.<\/p>\n

The CIGS thin film solar-cell modules are designed to give a voltage which fits the maximum voltage of 5.5 V for backup-capacitors — a battery of these capacitors will be charged from the solar cells and then provide the power supply for the LEDs. I came up with the following circuit:<\/p>\n

\"\"<\/a>
Solar cell powered LED light<\/figcaption><\/figure>\n

The central part is a DC-DC converter around a MC34063. This integrated circuit compares the external voltage at its pin #5 with an internal reference voltage of 1.2 V in order to stabilize the output voltage. I connected a light-dependent resistor in parallel to one of the resistors in the voltage divider for this feedback voltage. In the dark the resistance of the LDR is above 300 k&Omega while sinking below 3 kΩ in ambient light conditions. In the circuit this results in an output voltage under illumination which lies below the LEDs’ threshold voltage. In the dark this voltage rises to between 8 V and 12 V, depending on the actual resistance of the LDR and the position of the variable resistor — and the LEDs will light up.<\/p>\n

The efficiency of this circuit is certainly not the best. The MC34063 is a simple integrated circuit to work with but it also has a considerable consumption. Even the voltage divider should probably be built with higher resistances — in the current design it draws about 0.5 mA by itself. But the performance should be sufficient for the task at hand: charging a single 1 F capacitor from a 1 Wp<\/sub> solar cell module takes about 90 seconds under a poor<\/em> halogen bulb and the discharge lets two strings of 3 LEDs each light for about 60 seconds.<\/p>\n

\"\"<\/a>
The complete system<\/figcaption><\/figure>\n
\"\"<\/a>
The circuit board<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

Today I designed a solar-cell powered LED lighting for a model of the planned energy education centre Energihuset in Uppsala. The model was built by Nyr\u00e9ns Arkitektkontor and equipped with 108 white light-emitting diodes, series connected in groups of three for a common supply voltage of 12 V. The model will be presented at the Swedish […]<\/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":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"enabled":false},"version":2}},"categories":[11,8,40,10],"tags":[],"class_list":["post-253","post","type-post","status-publish","format-standard","hentry","category-electronics_en","category-everything_en","category-leds","category-solarcells_en","entry"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p48grL-45","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/posts\/253","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=253"}],"version-history":[{"count":11,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/posts\/253\/revisions"}],"predecessor-version":[{"id":2568,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=\/wp\/v2\/posts\/253\/revisions\/2568"}],"wp:attachment":[{"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=253"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=253"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sciencetronics.com\/greenphotons\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=253"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}