Sunday, June 3, 2018

Graphical Waterfall Hardware and Programming

Productive sunday , tinkering with graphical waterfall programming and electronics testing... Too many versions of program on hard disk... 1000s of lines of programming code stored at multiple places..cant afford years of hard work lost due to hard disk failure...;)
The program is taking instructions from SDCARD and sending the data to graphical watetfall electronics card...

A success Finally- Low cost DC servo

At last, i am able to successfully control the servo motor with low cost electronics to the finest resolution the encoder can support. This quadrature encoder takes 192 pulses per revolution( PPR)of the motor. The PID values for this motor is P=20, I=20 and D=0.1
Ziegler–Nichols method for PID manual tuning:
Set all gains to 0.
Increase Kd until the system oscillates.
Reduce Kd by a factor of 2-4.
Set Kp to about 1% of Kd.
Increase Kp until oscillations start.
Decrease Kp by a factor of 2-4.
Set Ki to about 1% of Kp.
Increase Ki until oscillations start.
Decrease Ki by a factor of 2-4.

Tinkering with Low Cost DC servo motor

For the past many years i am using Stepper motors and i am happy with these motors until now. Stepper motors are Open loop control as they have no feedback mechanism to the main controller. Once they loose steps the error will remain there spoiling the purpose of there use. At high speed the torque become low and prone to loosing steps.
So i am shifting myself from Stepper motors toward Servo motors. But all the electronics stuff as well as servo motor itself is too pricey for a hobbiest like me. This post is to study whether an ordinary DC motor can be converted into reliable closed loop servo motor. I purchased a bunch of DC motors with Quadrature incremental encoder from a scrap. The difficult thing is to find segregate the DC inputs to encoder sensors and the A+ B+ encoder signal wiring. Luckily by tinkering i found all circuitry without damaging electronics