rpm switch needed

[Seedler]

Hi,  

I have been looking for a circuit that would say switch a relay on and off at different rpm's of the rotor of a turbine.

Does anyone know of such a thing?

Dee.

[Flux]

You can do it from frequency of the alternator.

I think Commanda has posted a version here if you can find it. Failing that find the data sheet for the 2917 tacho chip ( National Semiconductor probably) that will give you what you want in the applications bit at the end.

I think it is LM2917 but there may be variants.

Flux

[ghurd]

It is here...

http://www.fieldlines.com/story/2004/8/22/212629/116

G-

[commanda]

And the switchy part is here:

http://www.fieldlines.com/story/2005/3/20/22747/9793

Amanda

[Seedler]

Hi,

Thanks for the comments folks.  I'm not entirely sure but I dont think this type of switch will work for me.  The system I am wanting to switch is a 240v grid tie system.  The think is the voltage at the controller never drops below 240v dc when the inverter is connected to the grid, even if the turbine is stopped.  I dont know why this is but I'm guessing if the voltage stays the same then maybe the frequency does too.  Please tell me if I'm wrong.

I was thinking of something that could read rpm the way an annometer works with a magnetic reed switch.  I found a device yesterday from Inspeed called a wind switch.  I'm guessing it could be used to read rpm.  Its a tad expensive though.  Would anyone out there know how to make something similer with an adjustable range, but with a lot less $ signs.

Thanks for all your help

Dee