I know how to calculate for led with constant voltage but I am having a hard time figuring out how to add a green power on system ok and a red fault led to the variable power circuit I’m working on. It is a variable power supply with an input that ranges from 4.5v to 15v dc. The circuit is being designed specifically for repeatable resetting when a short occurs without using a fuse. Also I would like to add a Piezo buzzer part#13940 from Sparkfun to notify when its faulted and then a manual switch will reset. Would I add that inline with the led fault light? For the core of my project I’m using a Ti TPS25921L. I’m a noob at this and have limited experience but have made some circuits before. I have found little help surfing the net only more questions. Here is a link to the chip http://www.ti.com/product/TPS25921L/support
Can you describe in discrete steps the functionality you want?
Seems like you could use the fault indicator pin to trigger a transistor to light your LED and run your buzzer.
- I want it to show power on/no fault in green. 2. I want it to show with green off, circuit short in red and a buzzer sound until manual reset. The current will be variable so the idea is to stabilize the current to the LEDs so they aren’t super bright or dim. Maybe a 3.9k resistor in line will do the trick? It might fluctuate some but it will be mild. What kind of transistor would you recommend?