Why don't you run the fan on Halfwave using a diode in series with the fan across the Transformer, the same for the other fan using the diode on the other half cycle.
Thank you for the idea. I am not familiar with those concepts. Where can I learn how to do that? (I also decided to go with just one larger fan - 330mA ). I surely must have been wrong about the current draw for the smaller fan.Why don't you run the fan on Halfwave using a diode in series with the fan across the Transformer, the same for the other fan using the diode on the other half cycle.
I did some reading on this. I can't figure out how far this design will drop the voltage (from 39v?)Why don't you run the fan on Halfwave using a diode in series with the fan across the Transformer, the same for the other fan using the diode on the other half cycle.
I've got some 1N4004 diodes that are rated at 400V so I think those can work. How does this design know to supply the 12V to the fan rather than some other voltage?
It's the base-emitter junction that needs to be turned on, so the calculation isHere's what I came up with. My thinking is that a 4k3ohm resistor will provide 9mA (39V/4300). How am I doing?
I gave this a try with the 1N4004. I have the following voltages (all with no load):
Sorry. I got things confused. I am using 1N4004, not Zener.What!! You don't need any Zeners they will conduct both ways.
, just use the 1N4004 diode .
I added a 100ohm resistor parallel to the cap. New results:You need to put a load on across the capacitor , say a 100 ohms resistor the voltage across it will be around 14 V, and the fan should be able to spin .
I double-checked the pinouts and I think I have that part right. I am only using one fan so, as far as I can tell, what I drew is similar to your post #25 for one fan.So have you got the regulator the right way round.?
Try the method I gave in post#25 using just one diode .
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