Wednesday, July 23, 2014

The gears are turning ...

video
The current design task is to adjust wire deposition rate with the turn of a knob.
After getting stuck trying to figure out Arduino stuff I was able to bounce questions off  Jonathan Ward at OtherMill an Zach Radding at zachraddingdesigns to good results. The motor runs and is speed adjustable.
Yesterday the motor was bench tested with no load for several hours and no issues. Microchips and motor temperatures were on target.
Today I'm trying to test the full load of the wire feeder and push some wire. Unfortunately something in the system is not happy and lays down for a nap after running just a few minutes. It appears the H-bridge chip taking a temperature spike causing a shut down. Allowed to cool a few minutes and away we go again. First impression for the cause of the problem is the input power to the H-bridge chip is not regulated.
More testing needed ...
Update
The motor RPM has been slowed to the expected inch per minute wire speed which has lowered the chip temperature.
With this change the system has run for 3 hours with no problems.
This chip is a little too close to heat failure so when doing the final soldering a second chip will be stacked parallel to add a measure of reliability. On future builds a larger chip would be better ...

The Arduino code that works :

#include <Stepper.h>

// change this to the number of steps on your motor
#define STEPS 200

// create an instance of the stepper class, specifying
// the number of steps of the motor and the pins it's
// attached to
Stepper stepper(STEPS, 8, 9, 10, 11);

//Create starting position for motor / pot
int previous = 0;

void setup()
{
 Serial.begin(9600);
 //How fast will we try to move the motor
 //If your motor stutters, its too fast so just lower the value
 stepper.setSpeed(30);
}

void loop()
{
 //Read analog 0 (pot) and map it to the range of the motor
 int val = map(analogRead(0), 0, 1023, 30, 0);
 Serial.print(val, DEC);
 stepper.setSpeed(val);
 stepper.step(5);

}

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