Electronics update

So one of the reasons we haven't been able to update this blog is because we've been caught up in the "wonderful" life of being an engineering student. Between trying to pass courses, complete assignments, prep for midterms, hands on labs and trying to find co-op jobs, we unfortunately haven't had a lot of time to work on the printer. Hopefully it hasn't been too long.

So as seen from the recap post, most of the mechanical work has been completed, and electrical work is the next big hurdle. But enough of the intro, onto the pictures!


You can see here a bit of an overall setup shot in my uni room with the tangle of wires (I had to guess at their length so they're a little long). At the bottom of the picture is the PC power supply (Antec Basiq at 350 watts) that we use to provide the power for the whole machine. In fact we only use 2 12v lines and 2 ground lines coming from the supply (same rail), so in reality most of those wires on the floor in the picture are unused. Sitting on the middle platform is the arduino mega and the protoboard containing the electronics required to run our four stepper motors.










The protoboard layout can be seen in the photo on the right. We followed the schematics posted here on the reprap wiki to come up with the layout. In detailed terms its a fairly simple layout, with the 12V lines running along the top of the board with the stepper motors plugging into headers visible there. 12V from the power supply can be seen in the left border of the picture with the header connection, and 5v logic from the microcontroller is also on the left. Enable,step and direction lines from the micro are along the bottom of the board, with some bypass capacitors sprinkled here and there to help level any voltage fluctuations. The circuit for the heated bed and the heater block haven't been made yet since we're still missing the mosfets to control them and the 6.8 ohm resistor for the heater block (hard to find here in Waterloo). Plus it's probably a good idea to try and get the stages moving first before trying the heating components.


In the final photo you can see the wire connections of some the motors and limit switches for the xyz stage. The z stage limit switch is sort of dangling in midair since it requires me to know at what height the build platform will rise to (which itself hasn't be built yet). It doesn't look incredibly professional with all that coloured wire and foil tape holding it together, but its fairly solid and easy to follow.






So in the end how does it all work out? Well we haven't even gotten around to moving it yet, but initial tests pulling all the inputs (enable,step and direction) to zero have led us to find some weird oscillations in the motors. It seems that 3 out of the 4 drivers have the stepper motors oscillating back and forth between two states, which is a little worrying. We're trying our best to isolate the issue and hopefully fix it, and we'll be looking into using one of the waterloo labs to do some poking around with an oscilloscope. Hopefully that will lead somewhere because I really do not want to buy 3 more expensive drivers and resolder them in.

Hopefully the next blog post will show the stages actually moving -and if we're lucky- the heater block electronics installed.

Until next time,

-Eric