Monday, August 26, 2013

Weekend Update

The pile of parts on my shelf is starting to resemble a scooter.

This weekend went off to a slow start, but, among other things, progress was made on the scooter.

Dimensions for the rear caddy platform and fork were finalized through the magic of Draftsight (solidworks for noobs).

Totally legit.
As you can see, I've been very thorough.

All that's left in terms of parts is getting the fork and rear platform sent out for water jetting. The only concern I have is the motor mount, which, considering I don't have any reference material, has been left out of this sketch. Not a problem as some creative milling can probably fix any clearance issues.

Trolling will be courtesy of a jasontroller, which will eventually be abused  modded for the purposes of increasing output wattage via decreased shunt resistance.

An in-depth how-to can be found here:

Power, originally coming from some derpy li-polys off of hobbyking, will be replaced by some A123 LiFePO4 cells that I'll have to weld together and arrange log style. I should be able to barely fit in a 10S2P pack (~36V and 5Ah).

Hub machining was a great success; I managed to mill down the ends of the rear hub to accommodate for the 4" aluminum u-channel.


To be continued.

Monday, August 19, 2013

Derpy photo shoot

Now that DOHLAC (Derpy/-oneTesla/Hot Long/Ass Coil) lives at home, I finally decided to take pictures.
Bad lighting is bad >__<.

Half bridge of 60N65s kept well within spec to avoid damn-I-blew-the-bridge-again syndrome (up to 75% duty cycle at 340VDC)

Gate drive provided by a pair of UCCs and feedback courtesy of question-mark antenna.


2.5" x 10" PVC, 32AWG wire

fRES @ 316kHz

I can probably push the coil to give more spark, but due to my unwillingness to replace the bridge, it'll be kept at a lofty 7.5". 

Long pulse widths for fire-y streamer goodness.
Longest spark on this run from a nice straight streamer. Top-mounted breakout point seems to distribute the E-field in a nice symmetric way that promotes longer sparks. 
Special thanks to Bayley and Kramnik for helping me troubleshoot this thing at one point or another.

Thursday, August 15, 2013

Project Dump

Working from nine to five doesn't seem to be helping my projects.

Part 1: The still imaginary scooter 

After learning how2mill, I set out on machining one of the few components that didn't require the motor or battery (which I have yet to order): the fork!

I should learn how2CAD at some point too.

After rough sketches and some trigy math in the comp book, I sadly discovered that If I were to set the axle in line with the handlebar shaft, I'd end up with a scooter nose-up. Not to worry though, as forward offset fork is here to the rescue! Combined with some derpy angle finagling by cutting away part of the  rubber 'shock absorber,' I'd achieve a scooter that is both aesthetically and structurally sound. Well, aesthetically sound at least. 

The resulting hunk of 1/4" thick aluminum resembled something slightly too angular for my taste, but as the first thing I've ever milled, I think it turned out ok. 

Part 2: Derpy Coil lives!

Also known as "Long Hot," Derpy coil has finally come to life after scraping the secondary base feedback scheme. 

Here's how the troubleshooting adventure went:

1. Coil is completed, run off a variac at low power. Nothing

2. Scoped across primary: looks legit. The primary waveform only goes to shit when it's running off of its own feedback. 

3. Add turns to secondary base feedback CT and hope it doesn't reach saturation. Nothing.

4. Remove high-pass filter. Poopy sparks appear. 

5. Feed the coil a 316kHz offset sine wave. Success! Kind of out of tune 2" long sparks appear.

6. Abort secondary base feedback, go to antenna: nothing.

7. Give up on this driver board and repopulate another one (without secondary base feedback junk attached).

8. ???

9. Success!

Here it is playing Solfegietto by CPE Bach. Spark performance isn't quite impressive as duty cycle was turned down to maintain note clarity. Modified oneTesla interrupter pulse widths were overlapping each other, which you'll notice when the really low notes start playing.

After Bayley reflashed the interrupter for true continuous wave output, several things happened:

Hot Long finally got hot and long.

Then the bridge blew after getting to ~140VDC. 

The number of primary turns then grew to 27.

Then the bridge died again, but at ~200VDC.

Failure is probably due to transients - further testing will resume after TVS is added and primary current is scoped.

UPDATE: 8/18/2013

Long Hot will no longer endure CW abuse and will continue to live life happy at 75% duty cycle, occasionally pushing out the odd midi file. 

Thursday, August 1, 2013

-oneTesla Lives!

After weeks hours of deliberation, I sent out -oneTesla to OSH Park, hoping to receive a functioning board.

But, oh, I got so much more.

Dat gold plating.
It might have been the fact that this was my first fabhouse board, but, damn. That looks sexy. The board features silkscreen, gold through-hole plating, and purple solder mask, making it quite the specimen.

A fully populated "Derpy Coil" with secondary base feedback tentacle.
Look! The inverter is inverting...!

It even does that inverting thing.

Power testing to come soon...