RazEr rEVolution: Beasting The Everything

Alright, now that’s over and done with…

This is the part where I recap how RazEr ended up being finished and packed up the day of departure. I’m glad to say that it worked without problems, at least at demo speeds. Singapore was also a pretty unique experience, and I’ll address that in a separate post. In the mean time…

60 hours

Some time around last Saturday night the 8th of January, RazEr rEVolution looked like this.

Two of the three sensors in DNIR mysteriously stopped responding a while ago, so I had to open it up and replace them. It involved heat-decomposing the epoxy holding the sensors in with the NEW MITERS HOT-AIR SOLDERING PENCIL!!!!!! and then adding new ones. For some reason, the ATS177 sensors seem to be a little fragile – I’ve had trouble with them going out before.

Whatever, at least they’re cheap.

After putting the DNIR back together, I decided to temporarily mount a mini-Kelly on the back just to take it around the hallways a few times. The DNIR has almost gratuitous torque, even at the 30 amp software limit of the Kelly controller. The original RazEr was pretty swift for such a small vehicle, but this thing is always on the verge of launching you off – not to the degree of Melon-scooter, but spontaneous wheelies were recorded. I was prepared to take it to Singapore just like this, even though it would have been the shadiest looking thing to find in a suitcase ever.

A few of us had fun taking the thing around the hallways. Well, until…

Yeah, uh, about 3d-printed parts being structural.

In my defense, that was a full speed head-on collision with the wall. I think even the original Razor fork would have bitten it pretty hard.

Well, time to fire up Make-A-Bot and pop out another one…

36 hours

Look! It’s mini-melontroller!

First hinted at the bottom of this post regarding Melontroller, I designed Mini-Melontroller just as a way to compactify the design even further. The circuit and pins are exactly the same, but the length is about half an inch shorter, and there are routing and placement differences. Namely, I like how clean the passive components ended up on this design.

Wait, so whatever happened to Melontroller? It did work, but seemingly only at low speeds. The control was unstable at high speeds while running the MITERS Public Etek, and I suspect it to be an electrical noise issue. Either way, something happened – either the software crashed or the power supply suddenly shut down, but the Etek suddenly stopped from high speeds, probably shooting a transient stiff enough back into the controller to take out a phase and a gate drive.

I put away Melontroller for a little while, but after getting the Kelly-rig on RazEr to work, I decided to try out the new PCB just to see if it was a problem resulting from my routing and erratic component placement. It turns out the mini version would just barely fit into the place previously occupied by the RazErDEC board.

Granted it’s at an angle, but it does clear everything. The bottom of the controller is insulated by some sticky-back foam rubber, hot glue, and Kapton tape. I’ve also cleaned up some of the wiring here.

As another touch, I found some leftover 3/8″ long flat-head 4-40 screws and decided to countersink the bottom hardware. I figure it was only a matter of time before I tried curbjumping and scraped all the screw heads off…

12 hours


It took most of Sunday and some of Monday to debug the controller. I think I spent at least 6 hours trying to debug electrical noise problems before determining that the benchtop power supply was unstable at the higher voltages needed to run the controller. When I took it off the bench supply since it kept latching and shutting down and put the controller on a battery  pack, everything worked beautifully.

The same thing may have killed Melontroller the First.

Otherwise, the rest of the debugging was macro-electrical and involved faulty connections and accidentally powering the Hall sensors backwards, fortunately without damage. It turned out my Cool Blue Switch just couldn’t handle the capacitative inrush on contact (there’s no precharge circuitry on the controller), and it stopped working after only a few power cycles. Thus, I reverted back to a Deans-based master power link like the robots.

Make-A-Bot had long finished the new front fork (beefed up to 75% fill for strength), so I spent a while just getting a feel for the control. The synchronous regenerative architecture of melontroller means I can’t really coast on the thing, nor kick scoot, and the handlebar will punch me in the stomach if I let go of the throttle from a high speed (since it brakes the motor).

This will be resolved hopefully once I add the current sensors back in and can perform current control. The throttle will then command current dirrectly, and the no-throttle endpoint is rescalable from negative current (drag braking) to no current (coast) to …. well, what, cruise control?

Well, it works enough… Time to shove it all in a suitcase.

With the front fork removed, RazEr fit beautifully across the diagonal of my suitcase. The ‘blades fill the two triangles that result, and NK & company are stuffed in the gaps.

To my utter surprise, this whole rig made it to Singapore without incident, or even with a TSA sticker. Granted, it was 3 days late, making it there only on (this past) Sunday night, because it missed my Impossible Connection over in London. I’m also proud to say that it made the trip back too.

Next: Thingapore itself.