I current have a 0-8V DC signal which drives a small 8V DC motor and I want to use this signal to run a 12V DC motor. But the smaller motor voltage ranges from 0-8V which in turn I want to control the voltage on the 12V DC motor in scale (variable), eg. small motor running at 4 volts and the larger motor should run at 6 volts. The 12V DC motor needs its own power supply. At the moment I am using the signal from the 0-8V to switch a small relay which inturn gives me 12V to my larger motor. My problem is that the small motor is variable and the 12V is not. How can I make them both regulate together?