RepRap: Blog

I got the rest of the wiring for the Frankenboard checked out. A loose soldered joint in the H-bridge cost me another PIC, but otherwise there were no problems.

The G4 motor tested out on the parallel wired 4-5 amp board without any problems. Speed, direction and the lot.

I ran it for some time at a PWM setting of 226 (0-255). A few hints for people wanting to use the L298N chip. It's a great chip but you have to treat it with respect

• don't touch the chip while it is running or for some time thereafter, especially if you are testing the board after having built it up and have the possibility of a loose electrical joint in the H-bridge. It gets quite hot, even with a heat sink attached.
  
• ground the sense pins if you want it to work
• pay especial attention to the orientation of the shottky diodes when you install them. I've got what looks like a fair second degree burn on my index finger for getting that one wrong.

I am beginning to see why you'd want to optically isolate the L298N chip from the PIC. If something is not quite right in your build of the board you can wind up with some impressive voltages hitting your PIC. I've lost three figuring that out.

After proving the board on the G4 I shifted it to an unmounted Frankenmotor and then to the mounted Frankenmotor that drives the z-positioning stage (horizontal). I was able to operate the z-stage as is (which means lots of friction) in a translation speed range of 10-30 mm/sec. There didn't seem to be any problems with overheating of either the motor or the H-bridge chip.

The Frankenboard was also tested against the high torque Siemens gearmotor. It is likely that this gearmotor, rather than the Frankenmotor currently installed, will be used to power the y-axis (vertical) on Godzilla. While slow, the Siemens Gearmotor has a very smooth movement and is nearly impossible to stall.

One little added benefit that I discovered is that the magnet that activates the AS5035 shaft encoder chip sticks to the end of the threaded drive rod and centres itself perfectly without glue or any other kind of bother. Every little bit helps. :-)