One of my kids dropped their Kindle when plugged in. The USB jack became loose, and the Kindle no longer wanted to charge. Specifically, gymnastics involving propping the kindle up, twisting the plug and standing on one foot were required to make it briefly charge until you walked away, and being out of warranty this was a terminal condition for the little tablet. Before going wireless, we’d previously taken the Kindle WAY apart, tried to resolder the USB socket and after 2 hours of stressful work on tiny components we had a fix that lasted 4 days.
I had 3 Palm phone “slip on back’s” each with a wireless charging receiver circuit and a spare palm touchstone charger in my junk bin. I also had some beer in the fridge and free time on a snowy Saturday.
First we used a spudger to open the Kindle, separating the back cover from all the circuitry in the main case. Google “spudger”, buy one if you like doing this kind of thing.
The Kindle back cover had a stainless steel liner. Presumably this was for RFI compliance or a blast shield for LiPo over-exuberance. Invariably, this would not have played nice with an inductive coupling so we pulled it off and insulated the coppery-clad back with packing tape at the “X” marking the center of the back:
This “X” is where we would tape the inductive power receiver that we carefully peeled off of a Palm back. The “power receiving” coil is really thin wire, and it loves to break if you are rough with it. Don’t be rough with it.
We put the power receiver onto the plugged-in touchstone, noted and marked which of the two terminals was “+5.5ish” volts. Once marked, we soldered a couple of thin wire leads to the charge receiver terminals, and prepared to locate where the Kindle took in 5V and Gnd:
We plugged in a regular USB plug to the dodgy socket, and while one kid wiggled it around, I probed to identify where 5V occasionally came out on the backside. Ground is easy to find, as most of the big fat “filler traces” that screws contact are ground. The +5v is the one on the left below, GND is the ugly solder joint on the right:
Well, that was about it- we snapped the back in place, crossed our fingers and put the Kindle on the junky old Touchstone base:
The charge indicator on the side turned Orange, and the Kindle started charging. Now, the thicker back makes the Kindle sensitive to the exact location of the external Touchstone with respect to the charging coil so we marked a “put charger here” circle on the back with a silver sharpie. When located correctly the Kindle charges as fast as it did with the factory-provided charger!
Junk parts + broken Kindle + beer + dad = happy kids and a rejuvenated Kindle!
Palm Touchstone inductive charger: http://www.amazon.com/Palm-Touchstone-Charging-separate-Charger/dp/B002CMEIWK
Palm Inductive charging back: http://www.amazon.com/Palm-Computing-Div-Touchstone-Cover/dp/B002UNKGMC
Recommended beer: http://www.sierranevada.com/beer/year-round/torpedo-extra-ipa
This worked surprisingly well, and while not all USB-charged products may like being fed by a (less regulated?) touchstone power receiver it may work great. The Touchstone is FANTASTIC, charging your phone by just putting it onto a little charging tombstone is super convenient and avoids the USB jack damage that our Kindle suffered. This would probably work for many other tablets, phones, and other USB charged thingamabobs that have room for the (very thin) Palm touchstone receiving circuit. If you have an incapacitated USB jack, or if you are looking for a way to pass 5V without wires/via/breaching a plastic case then give this a try for $14.
The Kindle has been happily recharged daily with this hack for the last two weeks, and so far so good.
Are you into things that fly, and are small enough for a person to carry?
Quadcopters, Helicopters, Fixed Wing, Multirotors, or anything else? Participate in our quadcopter build workshop, and want to continue to learn? Wanted to get into multirotors, and not sure how to get started? come on down!
VHS will be hosting our second afternoon meetup on March 15th. Bring down your flying objects of all descriptions, check out others gear, share your knowledge , and learn from each other.
Meet at 1:00 PM at VHS ‘the bunker’ – 270 E 1st Ave. We’ll spend some time in the shop ‘bench flying’, then if the weather co-operates we’ll head down to near Science World for a bit of flying.
Don’t forget – crashing is an opportunity to do more building :-)
VHS membership is not required (but encouraged!), and it’s a great opportunity to check out the space.
March 8th and 15th, noon-5pm at Kwartzlab (33 Kent Ave.).
Learn Verilog programming with the Altera development and education board. No prior knowledge of hardware programming is required.
Please bring a laptop with Quartus II v13.1 Web Edition and Modelsim Altera Edition (starter) installed. Include support for the Cyclone III + Cyclone IV.
This event is free and open to the public. There are still some spots available, get them at Eventbrite. Please register for both days.
I can be contacted at email@example.com
We’ve been busy this weekend putting together signs for the Faire as well as a lot of detailed planning. Just two weeks to go, after all.
Some action shots below of the laser cut signs being made, lumber arrows cut and painted, floor diagrams and maps, first aid/safety discussions, and so much more.
Wanting to up the ante a bit after having the Makerspace laser cutter chop out hundreds of city blocks to form a big map of MKE, I decided to laser cut a 24” by 18” halftone image! As it required the laser cutter to carve 10368 circles out of an off-yellow piece of 98 Lb paper, the cutting took 1.3 hours and produced quite a bit of confetti. I’ll display this with a purple (rather than black) paper behind the off-yellow laser cut paper. In person there is an interesting transition from an abstract purple/yellow shape into a black and white image as one moves further away from the image. You may even want to sit back from your monitor to improve the “image quality.”
Check out this video of the laser cutter in the middle of cutting 10000 circles! Note the mysterious logic employed by the laser cutter to determine the order of its cuts.
I imported a photo into GIMP, and desaturated it to produce a black and white image. After bumping up the contrast and darkening it slightly to nearly saturate the darkest areas (and avoid any totally white areas), I brought it into Inkscape. Inkscape can create halftones in a two step, manual process. The first step is to draw an 8 pixel by 8 pixel circle in the upper left corner of the 1133×720 pixel image, and select Edit->Clone-> Create Tiled Clones. To create a rectangular grid of halftone dots whose sizes are set by the color of the image below, use these settings:
From a quick test cut of a particularly dark area, I found that I needed to add an offset between each row and each column to account for the kerf of the laser. I.e. the laser beam has a cutting width that is wider than that of the line, and so in the darkest areas of the photo the halftone dots overlapped, causing a large section of the paper to fully detach. That led me to make this test strip with 11 shades of grayscale, evenly spaced between pure black and white. I laser cut this test strip with various offset distances between the rows and columns in order to arrive at the optimal 10% extra offset between adjacent rows and columns shown in the above settings. Note also that the smallest size circles may not even be exported from Inkscape due to their infinitesimal dimensions (i.e. if you export as a .pdf). The minimum gap between circles with 42% speed and 100% power on an 1133 pixel wide image blown up to 24″ is 0.79 pixels, which is 0.017″.
Applying these same settings to the image created a 128 by 81 array of circles, for a grand total of 10368 vector objects. In my first trial run last weekend, I found that sending this much data to our 60 Watt Universal Laser takes 5 minutes and results in a print error I noticed only after hitting start! After 1.3 hours of vector cutting, I found that a few of the rows and columns were shifted a bit from their intended location. It’s not clear whether this had to do with the print error, or if the paper moved slightly during the cutting process.
In order to improve the second version (shown at top), I chose to move away from the rectangular grid of halftone dots – recall that Kays and London teach that hexagonal close packing is for champions. The reason to abandon the rectangular spacing is to improve the dynamic range (i.e. to make the blacks blacker). For example, rectangular grids of circles pack at an “efficiency” of Pi/4, which is 79%, whereas hexagonal close packing results in a pi/6*sqrt(3) packing, or 91%. That means that the darkest sections of the image will be darker, as more of the light colored “front” piece of paper can be cut away. See the image below, and note that the hexagonal pattern does indeed appear darker.
It turns out that Inkscape doesn’t easily permit this. I ended up spending an hour or two fiddling with the column and row offset settings using my 11 black/white tone test strip to find settings that gave the hexagonal offset with the closest, even hexagonal spacing between adjacent circles. The following settings worked great for an 8 by 8 dot on the darkest square of the test strip:
I test cut this yesterday, sending ¼ of the data at a time to the laser to avoid printing errors. However, part way through the cutting, cut-out paper circles stuck to the long air assist nozzle of the laser head (ironically) hit a washer I was using to weigh down the paper to prevent movement while cutting. The paper shifted by about 1mm, which was enough to make some adjacent halftone dots overlap and cause others to have a visibly wider spacing.
In the process of cutting that photo, Shane happened by and mentioned that vector cutting 10368 objects may be just as fast as the typically-very-slow raster cutting time. With three clicks, I turned off the vector outline of the halftone dots, and selected a fill color. After test cutting a row, I found that he was right. Check out the difference between raster (100% speed, 100% power) and vector (42% speed, 100% power) in the darkest section of the image – the area with the closest spaced circles:
The vector halftone dots are perfectly circular, though the edges are a bit rough. Some of them have a very small border and so are a bit fragile. The raster halftone dots are not very circular, but the edges are very smooth and the boarders are slightly wider. I chose to raster cut the 24″ x 18″ image, and found that the raster cutting time of 1.4 hours was nearly equal to the 1.3 hour vector cutting time.
Note that many programs can create halftones, though often the results will not be suitable for laser cutter use:
The next step is to laser cut this image into wood. Also, Inkscape will let you draw any shape to create tiled clones from – so please do share photos of any halftone images you create with star shapes!
So maybe the robots haven’t taken over just yet, but there were signs of life in NJIT Robotics club’s giant cube-shaped robot chassis by the end of last Wednesday’s open night.
An old relic of the
trade federation Innovation First robotics competitions that NJIT used to collaborate with Newark high schools to build their robots, this gentle giant has been gathering dust for years until it fell into the club’s hands. Over the past few weeks, we’ve been organizing some interest on both NJIT’s budding robotics club brass and MakerBarBarians to revitalize the robot and begin a series of collaborative projects. We have invited them to use our workshop and aim to pool our resources and expertise, and so far a lot of progress has been made even in only one night.
The ultimate goal is to create a mobile robotics platform for all kinds of projects to come. Notably, the first project being talked about is a mobile base for an automated Nerf Vulcan turret. (sauce: http://www.instructables.com/id/Nerf-Vulcan-Sentry-Gun/?ALLSTEPS). Perhaps with some innovation, other features can be added like a method for autonomously collecting and re-loading darts. A lot of the details I will leave to your imagination as we still have a long way to go, but our gears are turning and I can hardly wait to see what we can come up with together.
Powered by two old Victor 884 speed controllers, this robot just needs a few nights of TLC and some spare parts to be ready to get upgraded to remote control. Once this benchmark is achieved, we will move on towards autonomous navigation, adding shaft encoders and sonar sensors on the bumpers and maybe sharp IR or cameras and/or a Microsoft Kinnect. Future plans may also include GPS modules and 802.11 wireless, and if we can build/find/’acquire’ one, to experiment with LIDAR.
MakerbarBarians Bilal and Travis and Jordan and myself were on hand to meet Pat and Mike from NJIT Robotics who were eager to get things going. Once we got the bot inside the workshop (a feat itself at it’s size), we set about attaching the drive chains, building motor brackets, hooking the motor up to bench power, and other odds and ends. Once we put power to those old Victors and heard the fans buzz to life, we knew it was going to be possible to get some chains turning. In the most promising stage, we were able to turn on one of the motors with the speed controller for a few seconds before the sheer peak current tripped the ATX’s internal breaker.
Problems left to be solved are abundant, including battery power and charging of those batteries, power train wiring, finalizing the motor mounting hardware, and other tasks. Apart from this, we also will need to figure out where to attach encoders, sonar bumpers, and other sensors (including the radio transceiver). But these and other challenges are only the beginnings, and we hope to make the robotics club regular guests. Most likely their visits will take place on Wednesdays, but stay glued to Meetup to see information about any future robot hack nights, which I will be posting up soon.
If you are interested, email me and I will make sure to include you on all the robot action and updates.
Peace, love, and nerf-gun-wielding robots,
One of the biggest problems with FDM 3D printing is hot-end jamming. There seem to be a lot of causes, most of which are not readily identifiable when a jam occurs. One thing I have found is that after a hot-end jam I can usually grab the filament and manually push it and get it flowing through the hot-end again, though it is too late to save the failed print. The most common means of driving the filament into the hot-end is to pinch the filament between a gear and a bearing and have a motor drive the gear, either directly (with 1.75mm filament) or via a gear reduction/torque multiplier arrangement (3mm filament). When the hot end jams, the large force applied by the gear over the small area of the filament that is pinched between the gear and bearing usually chews a divot in the filament thus destroying the grip.
A couple weeks ago I started designing a 3mm filament extruder for 3D printing. My hope is that this extruder will provide sufficient force on the filament to prevent hot-end jamming from ruining prints. My design uses two counter-rotating 6-32 nuts twisting on the filament (like the way your hands twist in opposite directions when you give a “snakebite” to your friend) to drive it into the hot-end. One is a normal, right-hand threaded nut, the other is left-hand threaded. When the nuts turn in opposite directions, the torque that would try to twist the filament is cancelled while moving the filament forward and reverse without twisting.
The motor has to turn about 1.26 times to move 1mm of filament so there is a huge torque to axial force conversion. The gear diameter is about 30mm. That 1.26 rev moves the gear about 119mm at its perimeter. That means there is about a 119:1 increase (ignoring losses in the gears, bearings, and nuts) in the force at the filament compared to the force at the gear. That force is applied over a larger area of the filament than the usual pinch arrangement, so it is less likely (I hope!) to carve the filament and lose grip. I tried stopping the filament by grabbing it with my fingers and holding as tightly as I could but it didn’t even slow down.
The firmware in the printer has to be tweaked so that it knows exactly how many steps of the motor are required to drive 1mm of filament. The formula is:
32 rev/ 1 inch X 1 inch /25.4 mm X 200 steps/1 rev X 16 microsteps/1 step = 4031.496 microsteps/mm
For initial tests I just input 4031.5 using the rotary encoder on the LCD interface to the RAMPS board in MegaMax.
Here are the parts that I used:
Left hand threaded tap: http://www.amazon.com/gp/product/B006YITGY8
5mm brass tubing: http://www.ebay.com/itm/360828686174
5x16x5mm (625Z) bearings: http://www.ebay.com/itm/321062568303
I also used a NEMA-17 motor from a QU-BD extruder.
You can DL the STL files for the printed parts here: http://www.thingiverse.com/thing:261037
Test printing will start in the next day or so and I will post another video showing success or failure.
There’s a lot of work that goes into putting workshops on at vhs. In the photo below you can see some of the parts for the SMD March Internet of things board laid out ready for packing. Many SMD components have no identifying markers – once they leave their supplier packaging it is tough to identify them. Here they’re all colour coded, cut into strips and then bagged. Each kit comes with a colour coded photo that helps you match the components to the PCB. I’m assembling 20 kits to start with, these are almost all sold but I will buy more as needed – you can find out more at https://vhs-smd-march.eventbrite.ca
You can also see tweets from my test board at https://twitter.com/vhsthings – I’m hoping we can add these boards to stuff like the laser cutter and furnace, this will let them tweet when they’re in use! The random number on the end is there to avoid tweets being marked as duplicates.
See you next month perhaps?