PWM to control LED with use of mosfet
Posted: Sep 30th, 2012, 8:46 am
I have build a light for my ROV with use of a total of 34 leds 3,2V 20 MA.
I`m planning to supply these with the onboard battery, and then I need to add resistors. Problem is that the resistors gets realt hot. Above 110 dg C (230dg F). So I planned to use a mosfet and PWM to try to get the mosfet to adjust the voltage from 0-3,2 volt (and to get dim function).
I made a shematic and tested this with adjusting the output PWM from the software and potensiometer.
Problem is that I`m not able to get the voltage lover that 4,23 volt (its going directly from 4,23 to 0 v). Its vorking fine from 4,23 to 13 volt.
Will it help to use an other type of mosfet? or is there anything else I can do to get the voltage down to 3,2 volt?
I`m planning to supply these with the onboard battery, and then I need to add resistors. Problem is that the resistors gets realt hot. Above 110 dg C (230dg F). So I planned to use a mosfet and PWM to try to get the mosfet to adjust the voltage from 0-3,2 volt (and to get dim function).
I made a shematic and tested this with adjusting the output PWM from the software and potensiometer.
Problem is that I`m not able to get the voltage lover that 4,23 volt (its going directly from 4,23 to 0 v). Its vorking fine from 4,23 to 13 volt.
Will it help to use an other type of mosfet? or is there anything else I can do to get the voltage down to 3,2 volt?