Synaptron Mega enters development phase

synaptron_mega

A couple of weeks ago I built the first prototype of our Synaptron Mega (the board with the red glow in the photo).  This is our Synaptron Micro operating system with a larger H-bridge.   The operating system is designed to run on Microchip’s dsPIC33FJ64MC802, and creates a very versatile and programmable motion controller.  It is designed to control brushed DC motors.

I hadn’t had a chance to test the board until this week. By the time I did get around to testing it there were problems.   Not “flame-on” kind of problems, but certainly things I wasn’t expecting.  First, every time I ran the microcontroller debugger the code would freeze.  This caused me to spend a  couple of hours troubleshooting the firmware.  It turns out I had missed changing a couple of settings related to the H-bridge drive signals, and was creating a shoot-through condition whenever the PWM output was turned on.  Shoot-through is when both the upper and lower side of H-bridge leg are turned on. Once that was sorted out, things started to go pretty smoothly.  The shoot-through actually turned out to be a blessing in disguise since it was essentially testing a short circuit.  The H-bridge  limited the load current to 11A, and after a second or two thermal shutdown reduced that to 1.5A.  No traces or surrounding components were lost.  It was kind of a nice upside to wasting time troubleshooting.

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