I have an electric fan in my bedroom when even on its slowest setting is far too powerful,can anyone tell me how to adjust the fan with some sort of device or switch to lower the rpm's,your help would be most appreciated.
Dave.
Is this a ceiling fan or a stand alone fan?
The simplest is probably a light bulb in series. The lower the wattage, the slower the fan will run.
Thomas
It is a desktop fan that runs from a 240volt mains supply.
In that case, I would buy a different fan with a slower speed. That would be the cheapest, easiest and safest solution.
BRW
--- Connect the fan to the mains through a zero-crossing solid state relay.
Use an optoisolator as a zero-crossing detector across the mains, divide its output by two to get nice sharp edges, and use the output of the divide-by-two to gate a counter.
Shine an IRLED through the fan blades and place an IR phototransistor in the beam on the other side so that when the fan is rotating it chops up the beam and turns the phototransistor on and off.
Use the output of the phototransistor to clock the counter which is being gated by the divide-by-two.
Connect the counter's Q outputs to the inputs of D type flip-flops, and use one of the divide-by-two's edges to simultaneously clock the accumulated count into the D flops and clear the counter.
Connect the "A" set of data inputs of a magnitude comparator to the outputs of the D flops and the "B" set of data inputs to the outputs of a manually operated binary coded switch.
Connect the B>A output of the magnitude comparator to the control input of the solid state relay.
Turn on the fan and adjust its speed by changing the setting of the binary coded switch.
Or use a µC... ;)
-- John Fields
Or chop every other blade off the fan :)
-- Gross... An odd number of blades will make the fan vibrate right off the table. Schematic at abse... Enjoy!
I could agree with that, pretty gross :)
O'Reilly)
setting
I think that with careful selection of blades it should still be possible to statically and dynamically have a balanced blade if you remove an odd number (possibly 3), one at one side and two several blades apart at the other. Could still be cheaper, more reliable and easier going for your option though.
get a dimmer switch,
blow the fan at a wall so you get the reflected blast.
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