{"action":"closed","issue":{"url":"https://api.github.com/repos/debaal/SolderingIron/issues/59","labels_url":"https://api.github.com/repos/debaal/SolderingIron/issues/59/labels{/name}","comments_url":"https://api.github.com/repos/debaal/SolderingIron/issues/59/comments","events_url":"https://api.github.com/repos/debaal/SolderingIron/issues/59/events","html_url":"https://github.com/debaal/SolderingIron/issues/59","id":57298669,"number":59,"title":"Tip safety in hardware","user":{"login":"yschroeder","id":8067560,"avatar_url":"https://avatars.githubusercontent.com/u/8067560?v=3","gravatar_id":"","url":"https://api.github.com/users/yschroeder","html_url":"https://github.com/yschroeder","followers_url":"https://api.github.com/users/yschroeder/followers","following_url":"https://api.github.com/users/yschroeder/following{/other_user}","gists_url":"https://api.github.com/users/yschroeder/gists{/gist_id}","starred_url":"https://api.github.com/users/yschroeder/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/yschroeder/subscriptions","organizations_url":"https://api.github.com/users/yschroeder/orgs","repos_url":"https://api.github.com/users/yschroeder/repos","events_url":"https://api.github.com/users/yschroeder/events{/privacy}","received_events_url":"https://api.github.com/users/yschroeder/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/debaal/SolderingIron/labels/hardware","name":"hardware","color":"fbca04"}],"state":"closed","locked":false,"assignee":null,"milestone":{"url":"https://api.github.com/repos/debaal/SolderingIron/milestones/3","html_url":"https://github.com/debaal/SolderingIron/milestones/Version%201.0","labels_url":"https://api.github.com/repos/debaal/SolderingIron/milestones/3/labels","id":971717,"number":3,"title":"Version 1.0","description":"Documented so everybody can use the project to make their own SolderingIron","creator":{"login":"yschroeder","id":8067560,"avatar_url":"https://avatars.githubusercontent.com/u/8067560?v=3","gravatar_id":"","url":"https://api.github.com/users/yschroeder","html_url":"https://github.com/yschroeder","followers_url":"https://api.github.com/users/yschroeder/followers","following_url":"https://api.github.com/users/yschroeder/following{/other_user}","gists_url":"https://api.github.com/users/yschroeder/gists{/gist_id}","starred_url":"https://api.github.com/users/yschroeder/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/yschroeder/subscriptions","organizations_url":"https://api.github.com/users/yschroeder/orgs","repos_url":"https://api.github.com/users/yschroeder/repos","events_url":"https://api.github.com/users/yschroeder/events{/privacy}","received_events_url":"https://api.github.com/users/yschroeder/received_events","type":"User","site_admin":false},"open_issues":7,"closed_issues":7,"state":"open","created_at":"2015-02-09T13:17:56Z","updated_at":"2015-04-28T18:50:24Z","due_on":null,"closed_at":null},"comments":10,"created_at":"2015-02-11T10:28:59Z","updated_at":"2015-04-28T18:50:24Z","closed_at":"2015-04-28T18:50:24Z","body":"You may have already heard about it: There is already one dead tip from experimenting with the PID controller.\r\n\r\nIf powered from a beefy 12V supply the tip heats up until it glows bright orange in a few seconds. If something goes wrong it dies in seconds!\r\n\r\nTherefore we should implement some mechanic to disable the heating when an absolute maximum temperature (like 550°C) is reached. We already discussed some ways to implement it.\r\n\r\nThe best option we could come up with so far is to use another channel of the op amp and let its output pull the reset line of the AVR when the temperature reaches the critical point. Reseting the AVR will instantly disable the heating. After that the AVR enters its reset interrupt and stays there indefinitely while printing an error on the display. This condition can only be changed by power-cycling the whole soldering station.\r\n\r\nThere is just one problem: The op amp will have to measure the tip temperature when it is heated which itself results in huge false tempature readings. The read temperatures are even dependant on the resistance of the cable to the tip as there is a voltage over that wire while the current is flowing. Maybe we can find an upper bound for that voltage and let it trigger when it exceeds this voltage."}}