total newbie needs help

Hi all, Got a bit of a problem that am hoping you can help me with...

I need a momentary switch, easy enough I hear you say, but due to the nature I need it to be timed...

Quick background, it's for the electronic gearchange on motorbikes. An excellent firm produces an electronic gearchange for disabled bikers. Gearchange is done by hitting one of 2 switches.

The problem is if the button is held for longer than 500ms then the changer just keeps going on and changing gears...

What am hoping to achieve is a circuit that can be put in-line, that will only allow a single "pulse" for less than 500ms..

Hope you follow that and can help me out a bit..

TIA

sparks

LM555 monostable mode.

Graham

If you don't know what your doing then you might want to think twice about your project.

If your going to use this to move up gear or down gear using this device and it produces a spike or some kind of noise, it could causes the gears to shift down when your travelling at high speed, it might become abit dangerous.

Naveed