Do PWM LED's run @ full brightness.
- Thread starter Black Dog
- Start date
With a normal fan, when you lower the voltage, the voltage is lowered on the led's as well and so they can appear more dim
with a pwm fan i believe the voltage going to the fan is constant but it is the pwm control line that varies the fan speed and by that logic, the led's should stay at full brightness
but this could be COMPLETELY wrong and ill wait for the fan/led guru Tealc to come and assist you
with a pwm fan i believe the voltage going to the fan is constant but it is the pwm control line that varies the fan speed and by that logic, the led's should stay at full brightness
but this could be COMPLETELY wrong and ill wait for the fan/led guru Tealc to come and assist you
Not in my experience, no. Lower the voltage, lower the brightness of the LEDs.
with a pwm fan i believe the voltage going to the fan is constant but it is the pwm control line that varies the fan speed and by that logic, the led's should stay at full brightness
but this could be COMPLETELY wrong and ill wait for the fan/led guru Tealc to come and assist you
You are right.
With a PWM controlled fan it will always receive 12v (if that's what you provide it with). The MOSFET that switches the fan on and off at 20Khz+ is on a separate part of the circuit.
Having only 7v where 12v is normal will drop the current running through the LED and reduce it's brightness. If the fan LEDs are white or blue the reduction in brightness will be more apparent due to the higher Vf of the LEDs.
It's tricky to reduce the voltage to a normal 3 pin fan and keep the LEDs at full brightness without replacing the LED power circuitry with discrete wiring, or at least replacing the SMD resistors for lower values more suited to 7v use. If you are handy with a soldering iron and the resistors are available to change then that might be a simple enough job if you always want the fan at 7v.
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