ive tried using relays, and it works, the motor runs in stop and go mode (pulsating), BUT the problem is, it has no force to pull even a lighter weight load (my motor can actually pull 230 grams even if the load has no rollers), ive tried another approach by using both relays and monostable mode LM555 timer, and it works, BUT another problem is- the motors pull the load in a very fast movement. What do i really need is a slow pulsating (stop and go) movement by pressing two push button alternately