Dr. Iguanas Vivarium


Posted on Feb 6, 2014

As the robot`s battery voltage would slowly drop, the servo`s centre point would drift. After a while, one or both servo motors would begin to creep even though they should have been stopped. Secondly, servos are designed to hold a position and not a set speed. Normally the position would be set by the length of the control pulse. 1. 0mS wou


Dr. Iguanas Vivarium
Click here to download the full size of the above Circuit.

ld be one extreme and 2. 0mS the other. Normally 1. 5mS would be in the middle. After being modified for continous rotation, any pulse length shorter than 1. 5mS causes the servo to rotate one direction, and anything longer causes the servo to rotate in the other direction. The magnitude of the pulse width deviation from 1. 5mS has an affect on the rotation speed, but it`s a bit variable and not linear. For this project I decided to use some 1:100 gear head motors I bought from Pololu. com. I also decided that I needed feedback so I could accurately know how fast the wheels were actually rotating. One way to do this is to use optical sensors that detect a pattern attached to the wheel. If there are two sensors and they are positioned correctly then you can implement something called quadrature detection (like was used in the old wheeled mice). Then you can tell not only the amount of rotation by counting pulses but also its direction by observed the phase between the two sensors. Fitzy and Carraldo are using the MicroChip dsPIC33FJ64MC804 as their brain. The MC variant includes dual built in quadrature encoders that are just what I need to turn pulses from optical sensors into direction and distance. Now I`ll be the first to admit that mechanical design is not my strongest skill. When designing the PCB I had only located the position of the motors but I hadn`t really decided exactly how I would attach them. Caught up in the...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Voltage window switch
    Line-hum-touch-switch
    Wireless Fm Microphone
    Simple Curve Tracer Circuit
    The UC3825BN as DC/DC Converter Central Processor Circuit Schematic and Datasheet
    All Lights Go Out When Brakes Lights Should Be On
    555 and 556 Timer Circuits
    white light led driver with
    Human Voice A1 Loud Clear English Talking Watch 2 Alarms Rooster Crow 12 24
    Nixie Clock Version 2
    Digital centigrade thermometer
    Leakage protection switch circuit diagram
    SK-IV with automatic voice-activated lights with music sounding circuit diagram



    Top