tag:blogger.com,1999:blog-3153881528840143069.post5997743399399396267..comments2023-08-02T20:54:52.429+10:00Comments on Grant Trebbin: Automotive LED Indicator Lamp AnalysisGrant Trebbinhttp://www.blogger.com/profile/13253301568478517009noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-3153881528840143069.post-1082731307373377742017-02-17T16:47:04.845+10:002017-02-17T16:47:04.845+10:00Spot on. The LM317 is rated for 1.5 Amps output. ...Spot on. The LM317 is rated for 1.5 Amps output. If R1 drops below 0.83 Ohms, the output current will rise above this limit and the device could be damaged by overheating. Odds are the thermal protection will cut in and it'll shut down. You still don't want that happening though.<br /><br />If using a variable resistor in a circuit like this you can limit the current by adding a fixed resistor in series before it to limit the output current.<br /><br />At the other end of the range the LM317 needs to output approximately 10mA at all times or it won't be able to maintain regulation. The means that R1 shouldn't be above 125 Ohms either. This can be ensured by putting a fixed resistor in parallel with variable resistor.<br /><br />It's kind of academic though. A variable resistor that can handle that amount of current and has a resistance that low is going to be quite expensive.<br /><br />I hope this helps.Grant Trebbinhttps://www.blogger.com/profile/13253301568478517009noreply@blogger.comtag:blogger.com,1999:blog-3153881528840143069.post-61205987563654655242017-02-17T11:35:12.974+10:002017-02-17T11:35:12.974+10:00In the current limiting circuit, what happens when...In the current limiting circuit, what happens when the wiper for R1 is all the way to the right? The R1 resistance is now close to zero. By the formula I_limit = 1.2/R1, aren't we going to draw the maximum amount of current? (a bad thing)Greghttps://www.blogger.com/profile/00067307752997427902noreply@blogger.comtag:blogger.com,1999:blog-3153881528840143069.post-52793172923447731962017-02-17T11:33:26.836+10:002017-02-17T11:33:26.836+10:00This comment has been removed by the author.Greghttps://www.blogger.com/profile/00067307752997427902noreply@blogger.com