Deathblades Motorworx

To continue the tale of the Deathblades skate motor, I’ll just pick up where last night left off.

With the anchoring epoxy set on the rest of the motors, I began to lay out the Hall sensors on the first. I’m taking semi-nonlinear steps in completing the motors – building one up completely while only taking steps which I know were successful on the rest. This is different than the way I generally do things – which is all at once, consequences be damned, but the motors are very much experimental and have had alot of hours put into them already.

So here’s we hardwire Hall sensors! Yesterday, I wedged them in place just to check for spatial sanity. I followed the placement up with a drop of superglue to hold the sensors in place for soldering.

The leads were cut flush with the end of the stator laminations. Then I point-to-point connected the VCC and GND pins of each sensor with Kynar wire-wrap wire (my favorite for making quick P2P connections, and which I had commissioned a restock).

In a standard LRK motor, 120 degree Hall sensor phasing results in an actual 120 degree sensor arrangement. With other winding configurations, this could be untrue – sensors could end up in the middle of teeth, for instance. Stretching a wire all the way around the motor to accomodate true 120 physical degree sensors is kind of unwieldy, so the next best option is to flip the center sensor and place it on the direct opposite side – which really means right between the other two sensors, convenient for wiring.

As I investigated when building FVM, 60 degree sensor spacing with the center channel inverted is equivalent to 120 degree sensor spacing.

Using some 6-conductor flat insulated cable, I connected VCC, GND, and channels A, B, and C.

But wait – that’s only 5 pins. I just declined to use 1 of the conductors, but could see this being a thermistor lead or something in the future.

After making the connections, I flattened everything out to discourage side plate rubbing, then dunked the whole mess in epoxy again, and left it to set under heat and tension.

Real motor builders would never use shady 5 minute epoxy, but I’m not a real motor builder, so it’s okay. After everything cooled down, I reinstalled the stator into the motor and terminated the sensor connections in a 6 pin header.

Originally, this was a 5 pin flat (single row) header, but I discovered the idiotic way that a 1/2″ nut does not fit over 0.6″ of headers.

Oops. Off they came, and in their place, a 2 x 3 header row was installed. One row contains the sensor leads, and the other sensor power.

What’s left to do now but TEST! TEST! TEST!!???

Well, first I had to check if the sensors actually gave valid outputs. To do this, I ran the motor off RazEr’s controller and viewed the outputs on the MITERS Scope-on-a-cart (like soap-on-a-rope, but much more hardcore).

After making sure the sensors were phased correctly, it was time.

I broke out the DEC Module that was previously featured as a test subject. Two of these will be in each power unit , controlling one motor each.

Using the Breadboard Abomination from last time, I wired everything to the DEC. After playing the BLDC phase-and-sensor combination game, I discovered that the phase connections were cyclically shifted one position clockwise – A was actually C, C was B, and B was A.

Weird, considering that I installed the sensors in between the two teeth of their respective phases, but the DECs could just have a shifted state table from what I built in FVM. At least I didn’t wire up the sensors backwards or something…

Here’s a test video of me playing with the skate motor speed. Excuse the rocky start and apparent lack of rotational balance. Remember how much care I took in making the cases – they have a little bit of axial play which is being broadcast very effectively by the hollow frame.

And no, there is no reason why you would ever want a powered reverse on skates. But, it IS an option the DECs give…

next: all of them