I am still working on electrical theory, but....
Using rheostats to control the fan speed doesn't reduce the current draw (rheostats use resistors to reduce voltage). Using a two stage switch to turn on fans one at a time or both will reduce current draw when on one fan.
The cockpit of a Kitfox is not that big. Reducing the fan on the co pilot or pilot only will still affect the whole cockpit and both occupants will feel the result.
Just my thoughts to think about≥
Ralph
Thanks guys and thanks for the links to the reostat and upgraded fans. Why use such a substantial Pcb? Aren’t there simpler pots/reostats? Is there some advantage to this dedicated motor control? Just to dissipate resistance heat?
I know the cabins small but it helps when it’s not blowing right on top of you! I figure worst case it’s easier to put an extra hole in the panel now and not use it. Rather than not have a hole and want one.
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It appears to me that the amazon link is to a PWM (Pulse Width Modulator using MOSFETs in the circuit; so it should be very efficient) and not a rheostat and appears, to me, to be the way to go. Driving the small motor(s) in our planes shouldn't heat it past it's design limit at all. Appears to be a great solution but we'll need a EE to weigh in on this as well.
See my build log at:http://www.mykitlog.com/lowandslow/
Just my 2 cents, if you get a 4-wire fan, the two additional wires are a tach output (fan rpm), and pwm input. The PWM input can be a really simple circuit, is much simpler and safer than a PWM motor driver. Fan already has the drivers built into it.
Not to hijack this tread, but is it common to use these cheaper electronics in a plane? My experience is that these kind of import/cheaper electronics have a higher failure rate due to the construction/design and lack of safety circuits. Vibration, component fatigue, thermal, are some of the modes. They just aren't designed for a rugged operation. Their use of electrolytic caps, which have a limited lifetime rating too (~500-2000 hours at around 70C) and their failure mode can be outgassing/fires vs polymers or ceramics which can be safer (not what you'll find on those DIY boards).
Aaron & Ashley
Newbie pilots working towards our PPL. Kitfox ordered (OSH19)!
Corvallis, OR
No switch needed, it’s all the way off is off. Still working good after 450 hours. I would look at the other heater options. Someone had a enclosed fan with vents?
Dustin Dickerson
Building 7ss STI x 2
Oratex
29" shock monster
EP912STI 155hp
Garmin
N33TF......FLYING!
N53TF......FLYING!