retepsnikrep
Senior Member
This is a non picaxe query just looking for ideas.
I have a 33R 25w power resistor across which a voltage of between 3-25v can develop. Current/power as per V/R but within 25W. In my application the voltage across the resistor starts off at say 25V faling slowly over several hours until is goes below 5v.
I want to monitor this voltage and use it change a bi-colour led from say red to green when the voltage across resistor drops from say 25v down to 5v. Change over point at say 5v-10v.
I want the voltage across the resistor to also power the indicator led which will be a low power 2ma or so device so it's current drain is not an issue.
Ideas? Zener diodes and transistor switch? Mosfet switch and PD?
I'm looking for the simplest/cheapest practical solution.
I have a 33R 25w power resistor across which a voltage of between 3-25v can develop. Current/power as per V/R but within 25W. In my application the voltage across the resistor starts off at say 25V faling slowly over several hours until is goes below 5v.
I want to monitor this voltage and use it change a bi-colour led from say red to green when the voltage across resistor drops from say 25v down to 5v. Change over point at say 5v-10v.
I want the voltage across the resistor to also power the indicator led which will be a low power 2ma or so device so it's current drain is not an issue.
Ideas? Zener diodes and transistor switch? Mosfet switch and PD?
I'm looking for the simplest/cheapest practical solution.