Ordered one of these before and now need another one, but cant remember which one it was.

Would any of these work? Im worried I got the one that is now out of stock.

http://rswww.com/cgi-bin/bv/rswww/searchBrowseAction.do?obs=sObs&name=SiteStandard&No=0&N=0&Ntk=I18NAll&Ntt=reed%20switch%20m 6&

Needs to close the switch when a magnet passes by.

Any of those shoul do. They are basically all the same

Will a mechanical reed switch be quick enough? Thought you'd need a semiconductor hall effect jobby like wot you get from ETB?

Yup I agree with ginger - a reed switch will max out very quickly and you will more than likely need a hall effect sensor.

Beaten to it! A hall effect is your best bet, but it needs to be powered, normally 5 or 12v. Some will be powered from a wide range of voltages.

Thanks
Darren