Hello all,

i have been working with DC motors, and Microcontrollers, and all the things ware going smoothly because i have created two H-Bridges with the Relays, (and they ware working just perfect), but the problem arise when i have suddenly changed the input of the Relays (H-Bridges) means if i am going to change the input state from 1,0 (Clock-wise) to 0,1 (anticlock-wise) then with the Back EMF created by the motor, and the SPIKE of the motor suddenly drop the Voltage, (well its quite common,atleast i know that) but the problem is that i am also using same power supply for the Microcontroller, :-( (sounds bad right?)

well the motors are 12V and 4amps, and i am using same power supply with 7805 to 8051,

so how to overcome that problem ? (i mean to say the back emf and spike problem)

by the way i have read in one site that spike can be reduced by inserting the capacitor with the pins of Motor, (and its rare in toys, also) but the problem is that how to measure that capacitance needed to reduce spike ?

(well i think that there was a formula of capacitor calculation for inductive load, but i dont remember it :-( )

so could any one please help a me (sounds noob right ?)

Asif Ali