RPM switch..?

[ScuttleRX]

Im looking for something that I can put in a circuit, which opens at a preset rpm, and is closed at anything beneath that.

Now the rpm buzzer must work on something like that...so I figure there must be some way to do it.

Im not very handy when it comes to car electrics, but is it right there is a voltage output somewhere that varies with rpm....if there is im guessing I need a gizmo that will open above a certain voltage which will correspond to the rpm I want, if such a thing exists?

[Clarky]

Depending on the voltage of the buzzer probably 12v you could use a 12v relay.
wire the buzzer to the coil, and use one of the normaly open contacts for what you want bearing in mind the current drawn of what you are using.
So when the buzzer comes on the relay closes the contact.
But of course this will only work when it redlines.

[iaint]

You can get aftermarket shift-light kits that you use a potentiometer to set the rpm that the light comes on at - would be very simple to use the 12v outputs for the light to power whatever it is ou want to run...

Max was having one fitted last time I was down @ re:worx so could probably fill you in on the simplicity of fitting...

[ScuttleRX]

cheers chaps, think your onto something there Iain, I shall investigate further...

[ScuttleRX]

Something like this  would seem ideal then, just wire it into my circuit rather than to the light.

Only thing is price...dont want to pay £40 when I know most of that is to cover the actual shift light, reckon it would be worthwhile finding a potentiometer on its own? if they sell \'em somewhere that is. If not £40 isnt too extorionate, but you get what I mean especially if the component im after is only worth a couple of quid

[ScuttleRX]

Any of these fit the bill?

Maybe one of the throttle body ones could be adapted? excuse my ignorance this is not my subject of choice

[iaint]

You\'d need something that\'s wired to the correct voltage/current combo and you need more than a pot to make this fork.  The pot is used to tune the circuit to switch on at the correct rpm, it won;t do the switching by itself.  To be honest £40 doesn\'t seem too extortionate even though the circuit parts are likley to cost under a tenner!

[ScuttleRX]

Yeah, think the extra £30 would be justified considering the hassle it would save (especially as I dont what pots and forks are ). I shall still scower ebay though and try and nab a bargain

[ScuttleRX]

http://cgi.ebay.co.uk/ARMTECH-4cyl-SHIFT-LIGHT-EASY-TO-FIT_W0QQitemZ8005254406QQcategoryZ72205QQrdZ1QQcmdZViewItem

Would a 4cyl one be ok? this one might be going nice and cheap