The Post-Everything Update, Part II: Maker Faire(s)

I’m back in the zone.

After back-hauling 1185 miles over 2 days from Atlanta to Cambridge, Assachusetts (and discovering in the process that Budget Rent-a-Car’s computer system cannot comprehend a mileage with 4 figures, to my delight), I’m about to go back down about 20% of the way…to the NY World Maker Faire as part of the MITERS booth/table display.

Great… maybe I should have just stayed a few extra days and just went 80% of that distance instead.

The reason why I ended up bringing most of everything ever (i.e. more than just the robots for Dragon*Con)  down to Atlanta in the first place was because of Maker Faire practice.

The Atlanta Mini Maker Faire, hosted by Georgia Tech, was a week after the D*C robot event, so I elected to knock a week off the semester and show up after being invited by some of the GT Invention Studio folks.

The event was held in a not-too-large parking lot, and about 60 individual exhibitors were there. The above picture is of the crowd and a pretty nice electric Chevy S-10 pickup truck conversion.

With rideable objects now making up a majority of my project fleet, the event was a great chance to make sure all of them had some testing time without me in the loop. You are generally always careful and mindful of a vehicle’s limitations if you’re the builder, but no such luxuries are afforded when your vehicle is being tested by strangers who had about 30 seconds of instruction beforehand. I suppose a hallmark of a well-engineered vehicle is if anyone can operate it with 30 seconds of instruction and not have it explode.

Sadly, only about half of my “travel fleet” made it through the day.

Straight RazEr

As the previous test video showed, Straight RazEr did fairly well confusing GT students on campus. After raising the front ground clearance another inch, it could finally turn and go over the average sidewalk crack and things like that. I brought it to the MMF, and it performed admirably well throwing off several random people.

The trick with sensorless brushless scooters is that you cannot just stand on it and hit the throttle. At least, don’t do it multiple times, since the motor pulling stall current across the controller will heat it up quickly. While most everyone understood the lecture and handled this part fine, I’m fairly certain the one person who didn’t caused the demise of Straight RazEr. A few seconds after I handed it off, I heard cries of “smoke!” and “fire!!” from the crowd behind me. I turned around and without much reaction, watched the massive plume of Turnigy smoke billowing out of Straight RazEr’s upper rear deck.

The short-circuit current desoldered my Deans main power connector. Some of the smoke and “Turnigy splatter” looks like it also made it out of the power access holes.

That SR ended up exploding wasn’t really surprising – the fact that sensorless vehicles need to be “push started” is really an alien concept to most people unfamiliar with them, and the majority push off too slowly or weakly anyway. The same reason is why very few people can actually ride melon-scooter, which also has a much slower “pickup speed” than Straight RazEr due to the latter’s much wider gearing.

Oh well.

Because Straight Razer was built mostly as a troll and the controller can be replaced later, I’m not going to try to bring it to NY Maker Faire. It’s considered out of commission until further notice. I might try throwing a melontroller on it some time later, but that involves adding sensors to the motor.

Speaking of melontroller…

RazEr rEVolution

I don’t have pictures of RazEr at the event (it looks the same, trust me), but I’m definitely amazed at how well it has stood up. Not only was it extensively used to the point of battery depletion at the end, but both the motor and Melontroller 2.0 have survived what amounts to a continuous +/- 50g minimum shock test. Because of the very hard wheels I chose by mistake and ended up designing around (90D and 90A hardness for the rear and front!), every little sidewalk or road feature was transmitted without damping into the drivetrain. After the day of demos, I rode it twice around GT’s Yellow Jacket Park square essentially full throttle the whole time. Overall, RazEr’s design has proven itself to be very robust. I’m particularly relieved that Melontroller 2.0 is a stable version from which I can improve (you know, adding things like a real logic power regulator), so this is one goal for this fall and winter.

With Jamison’s new hub motor scooter sporting 60A Colson wheels, I’m also going to remake the front and rear wheels to use them. Maybe RazEr can actually be a useful vehicle after that.

However, for the time being, RazEr will be at NY Maker Faire, completely unchanged except for a full charge.


The biggest and most awkwardly shaped member of the travel fleet, Segfault was already flaky before I left, and it only got worse at the event. Not only is the controller, originally designed to last maybe a week, now entering its 10th month of use, but the drive motors are slowly giving out too. The left Banebots P80 gearmox lost an internal shaft retaining ring some time ago, which means occasionally the left wheel just completely disengages and spins freely. I’d keep the thing running by literally just kicking or hammering the wheel back in. But finally, at the MMF, this happened.

Alright, I’m finished. Before this, the controller had pretty much been totally reduced to a ball of twitching and noise. The breadboards are slowly falling apart (their contacts falling out the bottom side after the glued-on paper backing expired) and most likely the contacts are also oxidizing and being sporadic. With all of this, Segfault is officially decommissioned and the current version will not be repaired or upgraded. I will probably part it back out and repair the left P80 motor for future projects. The vehicle is too big and unwieldy, and has more than served its purpose of control theory demos, so if I end up building another Segway-vehicle (ahem) it will be much smaller and lighter.

In the mean time, anyone want a full aluminum Segway-like vehicle frame? Just add your own P80 motors and Arduinos.

Because of the state of utter wreckage it’s in, Segfault is of course not coming to NYMF.


This thing was a huge hit, and I’m proud to say that it also survived the day unscathed (though with quite a few more stickers). It looks very squat and unimposing, but few people could actually stay on and ride it because of how high off the ground the rider stands and the short “wheelbase”. The Beast-it-trollers handled the whole day’s operation in 90-95 degree weather with no problems after I upgraded the drive FETs to IRFB3207 4 milliohm parts, instead of the old IRF1407s which flamed out two Swapfests ago.

While the Advanced Beast-it-Troller has been assembled and bench-tested, I have not installed them or written the software for them… nor do I intend to for this weekend. LBS will be traveling to NYMF too, and I’ll probably be tooling around on it all day since it has about 25 amp-hours of battery onboard, and NYMF is half parking lot and half rolling grassy fields and gravel lots. Hell yes.

Other things that are also coming

I’m going to bring Überclocker and Cold Arbor along as display sculptures. Clocker is functional (not very battleworthy, but things do move) so it may participate in some demos.

The Kitmotor Demo Stand will probably be spinning on the table all day so more of you people will go and build scooters.

Finally, I’ll also truck along the erstwhile Make-a-Bot, which has been making parts for all the other projects almost trouble-free since last December. It’s now a generation and some behind the kit 3d printer features curve, and I intend to rebuild it in the near future. Maybe I’ll park it in the 3d printer nest, next to all the Makerbots to troll Bre Pettis. After all, it’s about 75% faster than a stock Thing-o-matic and 1000% more \m/etal.


Pre-Everything Updates, August 18

I’ve been slowly knocking down the amount of half-taken-apart projects that have been taking up table space at MITERS. The usual shipping delays and distractions means I’m a little behind where I want to be,  but it’s not yet concerning. In other words, nothing has yet gone horribly wrong.

As of today,

  • Fix Überclocker!
  • Repair RazEr battery!
  • New motor controllers for LBS!

Pop Quiz 2

I received my shipment of carbon fiber from Dragonplate and proceeded to cut the top and bottom panels out on the same day. The CF this time is 0.023 instead of 1mm, so I lose some stiffness in the frame. I’m not quite sure why I chose the thinner panel actually – the scrapped PQ2 frame had 0.039″ CF top and bottom plates.

This was certainly one of the cleanest CF cuts I’ve made to date. I took several precautions this time to minimize delamination around holes and pierces, including fully double-sided-taping the carbon fiber to a solid wooden panel. Previously, I have either just clamped the CF to wood or taped the CF to a waterjet brick. The full support of the wood layer beneath the CF helped immensely – these cuts have almost no delam areas. The other methods would either allow the CF to flap up and down or still leave high percentages unsupported on the bottom.

The upside to this method is that I get a cute MDF billet Pop Quiz out of the process at the end. This was the backing for the carbon fiber after I stripped off the wet tape.

With Pop Quiz’s frame all printed and the CF panels cut, it’s mostly a matter of sitting down and assembling the thing. I got the VEX motor controllers in and also found my spare Spektrum BR6000 from who knows how many robots ago. Because PQ will be an experiment in using the VEX controllers, I’m going to rewind the weapon motor for 7.4v (2S) operation.

RazEr rEVolution

RazEr is officially all closed up and working again – the only thing the battery needed in the end was a charge and balance. God I love A123 DeWalt drill cells. What other kind of battery doesn’t mind getting zero-volted for a month straight? I don’t doubt that I have had some lifecycle and capacity loss because of the extended flattening, but RazEr is not a very high current system anyway.

This is what the battery looks like after I ripped off the layers of soda bottles insulating the pack. There are 2 balance leads, but no actual power connections associated with them – my balance-capable chargers can’t charge through the balance connector only. So this whole pack was kind of unserviceable from the start.

It also has bare balance wires passing directly over cells, something I recently learned was a very bad idea.

The resolution for this pack was pretty simple – add those power connections. The two Deans connectors represent the upper half and lower half of the cell. This enables it to be balance-changed by 4chan every once in a while to keep the cells level.

To insulate the balance cable better, I laid a layer of rubber cement underneath them. That will at least immobilize the wires and also keeps them, for the most part, out of potential electrical contact. Due to RazEr’s limited internal width, I couldn’t reroute the cables to the paper sides of the cell, which is what I would like to have done.

The final result, after coating with Real Giant Heatshrink!!! instead of more Mountain Dew bottles. Working with this was very refreshing – this is the massive thick rubbery PVC shrink often used for enormous power cable repair and the like. It actually doesn’t look like I threw it together in 5 minutes.

The Advanced Beast-it-troller

They’ve arrived.

From last update, the independent-input H-bridge version of the Beast-it-troller is now ready for assembly. Both of my Digikey orders for required parts, most crucially the IR2183 gate drivers, arrived the same day. Will it work?!

I also ordered (and received, too) a spare CIM motor to replace the toasted one in the left side drive. With luck, Land-Bear-Shark will be running (…again) for this upcoming Swapfest.

Pan-Project Update: Little things here and there

Not much has happened in the last week or so with regards to anything reaching completion. Sadly enough, not even the melontank has escaped the wrath of final semester. I’ve been filling in some minor details on the vehicles, though, in part preparation for the Energy Night Showcase, which I’m attending with some cohorts mostly as an excuse to ride scooters around to annoy the staff, and partly because said scooters is actually a hardware display at the event.

razEr rEVolution

Ever since getting back from Singapore, RazEr has just been kind of hanging out around MITERS giving curious onlookers test rides. One day, however, it just stopped. I don’t recall if it was on acceleration or deceleration, but the entire controller simply shut off. Not in flames, to my utter surprise. Further investigation revealed that the ATMEGA328 chip that is the core of the controller just straight up died. I don’t know what the cause could have been to completely kill a microcontroller besides voltage transients above its maximum voltage – after all, the logic voltage is fed by the gate drive voltage, which is one step closer to the very noisy and high current battery rail. And I don’t use a hardcore switching voltage regulator like some other people do… rather, a completely rigged linear voltage regulator fed by a resistor.

So instead of, you know, fixing the thing to use a real voltage regulator, I decided to fix the symptom for now:

Dropped (almost literally) on the Arduino carrier board is a 5v transient voltage suppressing diode, and right next to it is a 100uF 1206 capacitor. Seriously – 100uF in 1206? What is wrong with the world?

The addition of massive buscap and a TVS should absorb any transients on the logic rail in the future. I’m saving the real parts for the full v2 redesign, for which I have additional upgrades in mind.

Another issue that Razer had faced before its untimely demise was some kind of strange, no doubt current induced behavior where the motor operation would become very unstable if full throttle (or really anything above mid-throttle) was applied. The symptom manifested itself as a sudden loss of torque, almost like the motor was spinning off a clutch somewhere and little torque was making it to the wheel. Now, I know I slammed that motor can together on a 20 ton arbor press, so there’s no way it could have been mechanical. Further investigations into the gate drive voltage revealed no significant “early shutoff” of the high side bootstrapped FETs, which could cause such behavior past a certain PWM duty cycle. I was out of ideas, so on a wild suggestion, I made a common-mode choke out of a nut and a few turns of 14 gauge wire.

It solved everything.

I’m not even going to ask. The Common Mode Nut will, for now, become a permanent feature on RazEr. It allows me to floor it with reckless abandon down the hallway (shortly before discovering the hard 90A urethane wheels, covered in floor dust, have zero traction in the waxed hallway corners).


Not much news here, but I finished mounting the sprockets!

I made the spacers in the Pappalardo Laboratory, during my 2.007 lab assistant session. I decided to tow the entire thing to campus in order to do this, and the other students taking the class found it amusing that such a thing could possibly exist. Mission accomplished.


Unrelated to the showcase, but still worth an update, is the death and revival of MaB. I had run out of PLA plastic (which sticks to everything) by printing like 8 versions of Chuckranoplan, and needed to revert back to my stock of ABS plastic. My surface heater had shed its thermistor a while back for whatever reason, meaning it couldn’t be software-controlled, and getting ABS to stick to cold plastic was a difficult affair. So I did what any reasonably intelligent person would do – hotwire the heater to 12 volts.


Luckily, I realized how backwards it was after a split second, so there was no cascading destruction of the entire electrical system, but it was long enough to bake the entire bank of ADC inputs on the extruder controller.

It took a while and alot of help from people with more patience for SMT soldering, but with the AWESOME MITERS HOT AIR REWORK STATION!!!! the ATMEGA168 on the extruder controller was replaced, and MaB was operational again.

While it was away, I got a reel of white ABS instead:

I like white ABS alot better. Everything doesn’t come off as a featureless black blob, and it changes color slightly dependent on temperature and how long it’s been cooking in the nozzle, so it’s one way to gauge if my temps are wrong within a wide band of errors (No, they’re not.) For some reason, it doesn’t smell as death-filled as black ABS. However, it does seem to lose a little more volume in the extrusion process for whatever reason.

That’s all for now. If anyone else is going to the Showcase, be mindful that I might broadside you at full speed on RazEr.

i’ll just leave this here.

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.


I’m on a boat. On a plane. On a train. On a horse. Made of diamonds.

Actually, I’m not on any of those yet, but soon. Long story short, I finished RazEr rEVolution in a hurry, dressed up the ‘blades, and cleaned up NK. Then I proceeded to shove all of it in a suitcase, which might or might not be currently causing unholy chaos a few floors down in baggage check.

With luck, all of it (and I) will make it to SUTD shortly.

RazEr’s update will have to wait until I get back in, but the summary is that it works and the DNIR has almost gratuitous amounts of torque.