System with different Voltages

Discussion in 'The Projects Forum' started by KansaiRobot, Apr 4, 2010.

  1. KansaiRobot

    Thread Starter Active Member

    Jan 15, 2010
    Hello everybody. and thank you for all your help :)

    This time, I would like to ask a few question concerning a system in which several parts use different voltages.

    So far I have

    1. A sensor part. Working with -12V and 12V
    2. A motor part that I think works with 110V
    3. A controller (5V??)

    My questions are
    1. Can I use the sensor output (an analog signal 0-12V) into a ADC pin of the microcontroller?? I guess not, since I think the max would be 5V
    2. How can the output of a microcontroller be used to send signals to a servo controller that works with 110V? is this possible?

    Any comment or advice will be greatly appreciated

    With my thanks in advance

  2. ifixit

    AAC Fanatic!

    Nov 20, 2008
    Simplified Answers...
    1. Yes. A resistive divider could work, where the ratio of the resistors will divide the 0-12V by 2.4 to get 0-5V.
    2. Amplify the micro output to the voltage level required, then buffer with a current amplifier to get the power required to drive the motor.
    The details will require more info from you on exactly what your circuit requirements are, and specs on the motor, MPU, power available, etc.

  3. KansaiRobot

    Thread Starter Active Member

    Jan 15, 2010
    Thank you for your answers. I will think about the second one but regarding the first one:

    dividing the voltage from 12V to 5V will also reduce the degree of detail of the signal for the ADC I suppose. If there is no option I suppose it is necessary, but just in case- and pardon if I sound ignorant- is there anything as a 12V microcontroller?? ( so far I have worked with 5V PICs)
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    You can get ADC ICs that work directly with 10V signals, but that is about the limit.

    The ADC voltage range does not affect the final precision.

    If you use eg. a 10 Bit ADC, you still have 1024 steps over the full range whether you convert at 12V or 5V. Each step will represent about 12mV from the sensor.

    To improve resolution, find a device with eg. a 12 or 14 bit ADC.