i'm building a device for blind people which vibrates if it sense an object is in the way of the device. my initial plan is to connect a photosensor to a 555 ic and its output is connected to a vibrator. what kind of circuit (astable/monostable/bistable) is the most suitable for this? i was thinking on using monostable so that everytime an the photosensor sense an object the vibrator will vibrate for several seconds. but then again you guys know more than me in this kind of thing so i'm hoping for some advice etc to make my mind.