{"action":"created","issue":{"url":"https://api.github.com/repos/p-v-o-s/sky-sweep/issues/3","labels_url":"https://api.github.com/repos/p-v-o-s/sky-sweep/issues/3/labels{/name}","comments_url":"https://api.github.com/repos/p-v-o-s/sky-sweep/issues/3/comments","events_url":"https://api.github.com/repos/p-v-o-s/sky-sweep/issues/3/events","html_url":"https://github.com/p-v-o-s/sky-sweep/issues/3","id":85648775,"number":3,"title":"USB power flakiness -- exploring ","user":{"login":"dwblair","id":639760,"avatar_url":"https://avatars.githubusercontent.com/u/639760?v=3","gravatar_id":"","url":"https://api.github.com/users/dwblair","html_url":"https://github.com/dwblair","followers_url":"https://api.github.com/users/dwblair/followers","following_url":"https://api.github.com/users/dwblair/following{/other_user}","gists_url":"https://api.github.com/users/dwblair/gists{/gist_id}","starred_url":"https://api.github.com/users/dwblair/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/dwblair/subscriptions","organizations_url":"https://api.github.com/users/dwblair/orgs","repos_url":"https://api.github.com/users/dwblair/repos","events_url":"https://api.github.com/users/dwblair/events{/privacy}","received_events_url":"https://api.github.com/users/dwblair/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/p-v-o-s/sky-sweep/labels/help%20wanted","name":"help wanted","color":"159818"},{"url":"https://api.github.com/repos/p-v-o-s/sky-sweep/labels/ready","name":"ready","color":"ededed"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":16,"created_at":"2015-06-05T22:34:29Z","updated_at":"2015-06-23T23:23:24Z","closed_at":null,"body":"When the SkyShield is powered only by USB, the servos do not respond correctly to instructions in the sketch. The servos work as expected when plugged into the battery pack (fresh alkaline AAA) and work correctly when plugged into both the battery and to USB power. \r\n\r\nThe errant servo behavior includes continuous rotation of the pan servo when the sketch should be telling it to move about 180° and then wait a few seconds before moving 180° again. The tilt servo sometimes rotates back and forth or rotates continuously instead of making regular separate short rotations in the same direction.\r\n\r\nThe errant servo behavior does not happen under USB power when the Nano is used on a [Funduino shield](http://www.amazon.com/Bheema-Multi-Function-Funduino-Shield-Expansion/dp/B00PC9DTI4) instead of the SkyShield. So it is not a problem inherent in the Nano, the servos, or the sketch.\r\n\r\nThe bad behavior happens when connected either to a real USB port at the back of my desktop or to a USB hub.\r\n\r\nSometimes the servos will temporarily operate correctly under USB power after battery power is also supplied and then removed.  So when powered by both sources, servo operation is correct. Turn off the battery power, and the servos continue to operate correctly under USB power, but eventually (at the end of a while loop in the sketch?) , the errant behavior returns.\r\n\r\nThe USB does not seem to supply as much power as the battery pack with four alkaline AAA. When switching from battery power to USB power, the rate at which the servos move slows, and the sound they make is reduced. \r\n\r\nThe SkyShields have a 1.5 amp LDO voltage regulator (<http://www.digikey.com/product-detail/en/0/497-1404-5-ND>) which outputs 5V and has a 0.5V dropout. I think this regulator is not involved when the SkyShield is powered by USB (but I'm not sure, schematic: <https://github.com/p-v-o-s/sky-sweep/blob/master/prototypes/sky-shield-v0.4-schem.png>). The USB connector is on the Nano which has its own voltage regulator."},"comment":{"url":"https://api.github.com/repos/p-v-o-s/sky-sweep/issues/comments/114671613","html_url":"https://github.com/p-v-o-s/sky-sweep/issues/3#issuecomment-114671613","issue_url":"https://api.github.com/repos/p-v-o-s/sky-sweep/issues/3","id":114671613,"user":{"login":"Fastie","id":1805899,"avatar_url":"https://avatars.githubusercontent.com/u/1805899?v=3","gravatar_id":"","url":"https://api.github.com/users/Fastie","html_url":"https://github.com/Fastie","followers_url":"https://api.github.com/users/Fastie/followers","following_url":"https://api.github.com/users/Fastie/following{/other_user}","gists_url":"https://api.github.com/users/Fastie/gists{/gist_id}","starred_url":"https://api.github.com/users/Fastie/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/Fastie/subscriptions","organizations_url":"https://api.github.com/users/Fastie/orgs","repos_url":"https://api.github.com/users/Fastie/repos","events_url":"https://api.github.com/users/Fastie/events{/privacy}","received_events_url":"https://api.github.com/users/Fastie/received_events","type":"User","site_admin":false},"created_at":"2015-06-23T23:23:24Z","updated_at":"2015-06-23T23:23:24Z","body":"Yes, those are big caps, typically 8mm diameter and 16mm tall.  If placed cleverly, one could fit between the Nano and the shield and add nothing to the footprint. And it would add only 50¢ to the BOM, keeping it under $10.00 total. \r\n\r\nI have not yet seen a description of how many components would be required to implement a boost converter, how much space they would require, and how much they would cost. \r\n\r\nI'm not capable of that circuit design, so i think the SkyShield with a boost converter is a second generation device. If Don can incorporate the deck chair changes we outlined in [another thread](https://github.com/p-v-o-s/sky-sweep/issues/12), I can order a few v2.3 PCBs this week so they are available when my field work is done mid July. If they test well, I might order a bunch and offer the first retail kits for sale in early August before the KAP season ends. \r\n\r\nAfter v2.3, the next priority could be to breadboard a big capacitor to see if it helps. Don has all the components he needs for that experiment except for the 470 uF cap. \r\n\r\nIn the meantime, version 2.0 is in beta for anybody who wants one: <http://publiclab.org/notes/cfastie/06-23-2015/skyshield-v2-beta>\r\n\r\n"}}