Switching circuit

[alok9406]

I want to make a switching device with following features:

One senor will sense speed(frequency of a moving car, then this is fed to my circuit(to be designed). This circuit has three relays which are actuated when three pre-decided values of frequency(or current) are achievedi.e. there are three events-1. when certain frequecy(sensed by speed sensor) is achieved, first relay operates,2. on higher frequency second relay operates and 3.on further higher frequency third relay operates.
Please help me,
alok

 

[JFDuval]

Hi!

You should use a frequency to voltage IC and 3 comparator gate. Adjust the thresold of each gate so it put on the relay (by passing by a transitor and a diode) at the good level. Good luck,