I am going to use this driver in my contest entry and need info. Does this driver use pwm? If so, what is the frequency? Voltage? Current out? At what point can I tap the signal? I’m asking these questions so I can determine if the pwm signal could be used to control a fan’s speed and have it increase as the output increases. The other choice is a thermal pwm controller.
Yes it uses PWM, I think the voltage is whatever your battery is giving at the time.
I like your idea. You could tap the PWM signal right after the MCU. it doesn’t give much current (not enough for a fan) but you could use it to control a linear regulator (like a 7135) specifically for the fan. So when the light is on max, the fan would be on max too. It wouldn’t require any firmware changes. The only downside is the fan would be on all the time the light is on, turning slowly even on the lowest levels. I’m not sure if 3-4v and 350ma (what a 7135 gives) is appropriate for a fan either. You might have to do some research on parts if you do that.
I’m planning to use a pwm computer fan which varies the speed based on the duty cycle of the pwm signal. It has +, -, tach, and pwm wires and the delta fan I have is intended for 12v but specs state it will start and run with voltages of 4.0v to 13.8v. I can use the cells to power it and the pwm signal would control the speed. Max current is .45a and rated current is .26a so it would cause a slight drop in current to the emitters but the 2s4p arrangement should handle it fine. According to design guidelines the max pwm signal voltage is 5.25v so if the signal’s voltage is the same as the input I’ll have to go with a separate fan controller.
I should clarify: the signal should be (close to) whatever voltage your MCU is running on. If you’re doing 2s2p, the driver should already be configured to step down the voltage to under 5v for the mcu.
Worth a try then. According to general design guidelines a duty cycle of 30% to 100% range is recommended so if this manufacturer followed guidelines a pwm duty cycle of less than 30% will result in the fan being off. That’s fine since the lower levels won’t really need active cooling.
To clarify this as well, if the PWM on the driver was at 100% duty cycle, so would your fan, which is appropriate. However if your driver was at 30% duty cycle, and not making enough heat to actually need a fan, your fan would still be matching it at 30% .
Maybe that’s desirable, or maybe you have already thought of that and you’re ok with that.
edit: didn’t see your most recent post. If it actually shuts off under 30%, that could be ideal
The light will use 4x xhp70 emitters so I’d imagine the 30% point would see significant heat produced. That seems like a good point to start the active cooling.