Fixing the problem where gparted (parted) won’t see a partition due to a mac partition table

Posted on September 18, 2013 by Jay

I purchased an external HD that was “mac compatable” but I used it with a linux system and used fdisk to put two partitions on it.

Later on, I wanted to use gparted to easily resize one of the partitions, but it refused to see any partitions at all on the disk.

fdisk could still see them just fine, but reported “Partition type: mac”

It turns out that the problem was that the disk originally came with a mac partition table in addition to (right after) the regular MBR Master Boot Record.

I noticed that the first partition didn’t actually start until 63 sectors into the disk (at the beginning of the 2nd cylinder).
Device Boot Start End Blocks Id System /dev/sdb1 63 1171893554 585946746 83 Linux

So I used DD to copy the first cylinder to a file:
sudo dd bs=512 count=62 if=/dev/sdb of=firstCyl.bin 62+0 records in 62+0 records out 31744 bytes (32 kB) copied, 0.000715733 s, 44.4 MB/s

Looking at that bin file in an editor, I saw the string “Apple_partition_map” which is a dead givaway of what the problem was.

So, I wrote out all zeros to the first cylinder:
sudo dd bs=512 count=62 if=/dev/zero of=/dev/sdb 62+0 records in 62+0 records out 31744 bytes (32 kB) copied, 0.00165608 s, 19.2 MB/s

And then I copied the first sector (512 bytes) back from the firstCyl.bin file I had made:
summetj@constantine:~$ sudo dd bs=512 count=1 if=firstCyl.bin of=/dev/sdb 1+0 records in 1+0 records out 512 bytes (512 B) copied, 0.00183878 s, 278 kB/s

And it worked! Now gparted is no longer confused by the apple (mac) partition table that I zeroed out, and sees my partition.

MakerGear Hot End Molex Connectors

Posted on September 9, 2013 by Jay

I recently replaced a MakerGear hot end with a different model (MG Plus) but wanted to maintain the same connectors (used for the resistive heater and the thermocouple). The MakerGear connectors had a positive locking clip, while the JST connector that came with the MG Plus thermocouple was only friction fit.

FYI – The MakerGear hot end and Prussa Mendel kit I have use the following Molex Micro Fit 3.0 Family parts:

The female connector (with the bump) is a Molex 0436450200 (DigiKey part number WM1845-ND).
The male connector (with the hook that catches the bump) is a Molex 0436400201 Digi-Key part number WM1855-ND
You will also need the associated female and male crimp connectors for the internal contacts: Molex 43030-001 tin 20-24 guage wire (DigiKey part: WM1837CT-ND CONN TERM FEMALE 20-24AWG TIN) and Molex 43031-007 tin 20-24 gauge wire male terminal (DigiKey Part: WM1841-ND WM1841-ND CONN TERM MALE 20-24AWG TIN)
( You might want to get the crimp connectors for smaller wire (higher gauge numbers) depending upon what wires your thermocouple uses, but I got 20-24 gauge for use on power connections and just soldered my thermocouple wires into them.)

The cartridge heater on the MG Plus nozzle came with enough wire to reach all the way down to my RAMPS board so I ended up only using the molex connectors for the thermocouple, and running the resistive heater wire all the way down. This left me with a set of wires going to my hot end terminating with a molex, and I eventually plan on using this for an “always on” fan for cooling the top of the hot end (as opposed to the “under RAMPS control” fan for layer cooling).

Bubble Display Jr – Designs

Posted on September 6, 2013 by Jay

As part of building the bubbleDisplay I made a lot of prototype tubes, nozzles, and even a small prototype display before actually committing to building the final product. This left a lot of random bubble display type parts laying around my garage. I hate throwing things out, and I wanted to have a bubble display of my own, so I’ve started to design a BubbleDisplay Jr that I can make out of leftover parts. Because I’m limited to stock on hand, I couldn’t make all of the tubes the same length (unless I wanted them all to be 9″ tall….) so I went with a Superman Memory Crystal style sculpture:

Of course, since I have a 3D printer now, I decided that printing the bracket to hold the air hoses and LED’s would be the way to go:

There….now you can’t say I don’t plan out my projects before starting them.

Bubble Display Overview Video

Posted on September 4, 2013 by Jay

I spent a lot of time last summer and fall building this 62″ wide bubble display. So much time that I didn’t get a chance to edit together and post an “overview” video showing the whole thing in action. Well, here is that video. If you are looking for more build details just read all my posts tagged with “Bubbledisplay”. If you just want to sit back and watch the whole thing come together via videos, start watching my “BubbleDisplay” channel on YouTube At the beginning.

Building a Signal Generator – Paper Prototyping instrument panels

Posted on September 3, 2013 by Jay

To test the resonant frequency of a Tesla coil or other resonant circuit you need an oscilloscope (which I have) and a signal generator (which I didn’t have). I was able to follow these instructions from RM Cybernetics to build one from a 555 timer and use it to test my primary and secondary.

The only modifications I made to the circuit was the addition of a toggle switch so that I could use two different capacitors, giving a “low” and “high” frequency range (plus a “air gap” capacitance that basically runs the 555 as a 2Mhz sine wave generator). I built the circuit on a protoboard that came with a box, and decided to use a laster cutter to make the instrument panel. To do this, I opened up Inkscape to design a control panel using vector graphics. I would print each design out and tweak it until it fit my box and circuit perfectly. I then tested various dial positions on my 10K audio scale (logarithmic) pot using my oscilloscope to mark the approximate frequency on the dial. After a few trials, I was able to laser cut the design onto a piece of 1/8″ craft plywood to get the finished product.

Yoda Bust(s)

Posted on September 3, 2013 by Jay

I have been printing Yoda busts on my Rostock Mini.

The first (small) sized one printed very well, but I had some problems when I tried scaling up to 160% size.

If you look closely, it has a small discontinuity just above the eyes. (It looks like the top of his head was sliced off and put back on slightly “off”.)

It looks like one of my axis lost a step, so I ran through various diagnostics (more airflow over the stepper drivers, higher current to the steppers, upgrading my slicing software, etc) and eventually the problem got worse:

Then I heard some squeaking from my 3D printer and started to move things around manually to isolate it and I realized that my straight rods and linear bearings were dry. The final solution was to oil my straight rod and liner bearings, although I can’t confirm that the upgrade to Slic3r didn’t also help things out. All in all, it only took four tries to get things right:

So now I have a large yoda head to float on my desktop levitation box:

Bubble Display Source Code & Bill of Materials

Posted on September 1, 2013 by Jay

This open office / libre office / open document spreadsheet lists (most of) the parts I purchased for the bubble display, as well as the supplier part number. As some of the parts were surplus, or purchased from China via ebay, the suppliers may or may not still have them available. I didn’t keep the BOM document entirely up to date after I started to put things together, especially for several last minute runs to the hardware store, but it generally shows all of the major components.
Bubble Display BOM

This is a source code dump that includes the arduino code that I wrote for the bubble display. It’s not very nice looking, but it may help others to learn what I did on the software side of things. You’ll also need a Shifter library for the 74HC595 shift registers and a WS2801 library for the RGB serial LED string.

bubbleDisplay.ino

The “images” are encoded as individual pixels, hard coded as an array, generated by python code from simple .GIF images. Edit the image in an image editor, and then run the code to generate the C code array data.

BDPictureMaker.py

Building another Toroid

Posted on August 3, 2013 by Jay

Since my first toroid was out of tune, I decided to actually follow directions this time and use an 8″ inner tube (2″ diameter) for my Toroid. I bought an 8″ inner tube and 50 yards of Aluminum Duct tape so I wouldn’t run out.

Then I went off-label and added a 4″ Big Daddio anodized aluminum personal pie pan which I’m going to try as a mounting system.

After drilling a hole in the base of the personal pie pan, I wrapped it and the inner tube with aluminum tape.

After this picture was taken I had to extend the aluminum tape down to cover the hole in the pie pan, as the anodized aluminum pie pan was apparently not conducting. After I did that I got less than 300 ohms resistance measurement from the outside of the toroid to ground.

The size of this toroid is much closer to spec, although the Big Daddio pie pan holds it about 1″ higher than a straight piece of cardboard. Unfortunately, when I measured it’s resonance, I found a big signal at 340 kHz, (2.93 micro-seconds) which is even higher than my first toroid! Obviously I’m doing something wrong.

Electric Truck Battery Pack Status Report

Posted on July 26, 2013 by Jay

I’ve been driving my electric pickup truck since February of 2011, and have almost 2.5 years on my first lead acid battery pack (twenty six-volt GC-8 golf cart batteries by Energizer/Johnson Controls/Costco). I’ve put just under 2000 miles a year on the truck (4449 miles since I got it, 16011 miles total as an electric truck) but have charged the batteries around six hundred times. My average trip is relatively short (7.43 miles) and I’m averaging around 800 watt/hours per mile driven (measured from the wall, including charger and battery inefficiencies.)

When I first got the truck I could drive 20 miles with ease, and if I pushed things and drove carefully I could get up to a 30 mile trip out of the battery pack without pushing it below 80% discharged. Over the last 2.5 years / 600 cycles the pack has degraded, and one battery basically failed. I replaced the failed battery (it had about 1/2 the capacity of the rest of the pack and was limiting my maximum range to 5-7 miles per charge) with a replacement for $100 and now the pack is performing at a reasonable rate for a 2.5 year old set of batteries.

My current max range is around 15+ miles (I’ve driven several 13-14 mile trips carefully without getting any low battery alerts), which is enough to make it to the hardware store and back with a long piece of lumber. My typical commute is a 4 mile round trip to the MARTA station, so it can very easily make this trip. I expect that in the next year I won’t be able to make it to the hardware stores, but will probably still be able to use it to get to the MARTA station for a one or two more years.

I plan on replacing the entire pack in one or two years, depending upon how things shake out. It appears that my battery costs per mile will be in the 0.30 – 0.40 range, which is under the federal mileage rate, but does not count the cost of electricity (around 0.09 a mile) or maintenance. I have actually been very happy with the cost of maintenance on the truck. I replaced the two front shocks myself, had a shop service the brakes when I purchased it, and replaced a few pieces of interior trim and a parking break lever with parts I got at a junk yard, but all told the maintenance costs have been under $300 for the last few years. Compared to the maintenance needed on our internal combustion engine (ICE) vehicle this is a pittance…I could have bought two new battery packs for the truck with all the money we have spent on the family car in the shop over the last two years.

Building a temporary toroid

Posted on July 25, 2013 by Jay

I decided that I couldn’t wait for the official oneTesla stamped metal toroid to arrive, so I built one myself out of stuff I bought at the hardware store.

(Specifically 3″ flexible aluminum ducting, and aluminum Duct/Plumbers tape. I couldn’t find any 2″ flexible ducting…more about this later) I ran out of tape, so I couldn’t make it quite as nice as I would have liked, but a lack of tape isn’t my only problems from an aesthetic standpoint. I’m really looking forward to having the professionally stamped toroid, as it should maintain the great aesthetics of the kit.

It actually looked a lot nicer back when I only had one round of tape holding the two ends together. I also had some extra “Great Stuff” expanding foam that I had just used to plug some holes in the house, so I filled the inside of my toroid with some foam to give it a bit of extra rigidity before I taped it closed.

I used a piece of thin plywood to hold the toroid, and wrapped it in aluminum tape (until I ran out).

I used the last of my tape to completely cover the top and bottom of the wood circle and bridge to the toroid. I also taped the breakout point coming off of my toroid.

Now, for the big annoyance. Because I couldn’t find any 2″ tubing, I substituted 3″ tubing instead. The toroid has a major dimension of close to 11 inches and the diameter is 3″. The oneTesla recommended toroid has an 8″ major dimension and a 2″ minor dimension. I don’t know how much this will affect the Tesla coil, but I’m hoping that as long as I run it at 1/4 or 1/3 of the max power things won’t break.

Update:
Unfortunately, this toroid was measured about 70kHz out of tune (233kHz for the primary, vs 303khz for the toroid that I made). I only turned the power up to 40% and the primary oscillated, (you can hear the buzzing) but I never got a spark. I have a smaller 2″ diameter inner tube and more aluminum tape on order now…

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