Rotary Switches? Wind/Air Speed

p

Hi all,

Does anyone know where I could purchase some ultra friction-less rotary switches (or similar device) for detecting airflow?

I'm trying to build something a little like this but anything I've seen, needs too much power to move. It needs to be moveable by someone blowing on it.

Any ideas welcome,

- Kevin

Dave

If you're looking to build it then maybe look into frictionless bearings and build the rest yourself?

p

Frictionless bearings you say. Got any more info on them, or where I could be a componant?

Thanks.

Dave

I think i'll find the stuff that you may want here

https://sdp-si.com/eStore/Direct.asp?Exp1=2&Exp2=3&CP=Bearings.htm

Dave

you could house the bearing in this then, maybe

p

Cool. Thanks for the help.

Dave

Any chance that you'd post up a picture when you're done.

Specky

Why on earth would you want to use a rotary switch for this??

All you need is a shaft with some sort of vein on the end, mount this in such a way that when the shaft turns the vein will pass through the slot of a slotted opto-switch.

Count the pulses output from the opto and time the pulse width to determine the speed at which the shaft is turning.

There is very little resistance to the turning of the shaft because you're not overcoming the friction of turning the switch.

The opto is sealed so you're not going to have to worry so much about contaminants getting into the mechanism.

You can get lovely schmitt trigger output models which will make the pulse processing a lot easier that trying to deal with bouncy old switch contacts.

Alternatively you could just buy an anenometer which will do the job for you.

You could even use a shaft encoder which will give you a direct digital output (in grey code) of the position of the shaft at any time which might be useful if you need to sense if the shaft changes direction of rotation.

p

Originally posted by Specky
Why on earth would you want to use a rotary switch for this??

Because you didn't reply sooner!

Seriously though, I'm no engineer, and didn't have access to someone I could burn the ear off. I went with what's simple and easy. I did look into the optical thing, but felt a bit out of my league. From what you say it would've been better.

In the end was able to hack a motor, to use as a rotary switch.

For pictures & more info see here:
http://www.redbrick.dcu.ie/~brandnew/kevin/log/

Specky

Because you didn't reply sooner!

Pesky engineering forum tucked away in the science stuff......tut.....

I'm no engineer

Having seen what you've done I would have to disagree! You appear to posess the most important asset of an engineer, ie ingenuity.