Sunday, March 24, 2013

Bike headlight helmet mount

I needed to put my light on my helmet.  Boom.  Thing # 65773

New thing-bike light mount

I have been meaning to do this for a while so I threw this together this afternoon.  It's nice to be able to solve problems so nicely in less than an hour.
Thing # 65732, bike light seat post extender

Kindle Paperwhite

I just purchased my 3rd eInk based ebook reader, a Kindle Paperwhite.  Previously I owned a Sony PRS-505, then a Nook Simple Touch.  Between the Nook and the Kindle, I've been using a Nexus 7 tablet with Mantano reader (I also played with Moon+ reader for a while).


I switched to the Nexus for two reasons - one, I find that I want to read in the dark FAR more often than I want to read in full sun, so an LCD screen made sense at the time for that reason.  Two, I figured it'd be nice to have a device that I could use to browse the web, check email, play games, etc.

I felt that the screen on the Nexus 7 was fine for reading.

I'm switching back to eInk primarily BECAUSE the Nexus 7 can do so much - I found that if I had a few minutes, I would play games instead of reading, and as a result I was not getting nearly the amount of reading done that I really wanted to.  After switching, I'm also finding that apparently I've been fooling myself about the LCD screen - it's not nearly as nice to read as the eink.  I find myself reading for much longer at a stretch, an hour or two instead of 10 minutes.

Regarding the device itself, I think it's very close to being the perfect thing.  It's extremely light, the battery is said to last for weeks, the built-in light is completely perfect - absolutely uniform and extremely adjustable from barely on to as bright as it needs to be (if you need it brighter than that, then the room is bright enough that you don't need it at all).

I have a bunch of ebook content already and I am having no trouble loading it on the Kindle.  All of my existing content is in Calibre, some purchased from Baen (with no DRM), some from Google Play (with DRM stripped via Calibre plugins), some purchased from Humble bundles or other non-DRM sources, downloaded from Gutenberg or MobileRead, etc.  The Kindle is automatically recognized by Calibre when I plug it in, and I can just drag stuff to the "device" icon to load it.  I can also hit my Calibre server using the Kindle's built-in browser from anywhere, find a book, click on the "mobi" tag and it just loads up.  I do have to be sure that I've got Mobi versions of what I want, but that was easily taken care of by hitting "select all" and "bulk convert" and letting it run overnight.

I did also load a book from the Kindle store - a copy of "The DaVinci Code" that was free this week, giving me something to try loading directly.  I also was able to pull it into Kindle for PC and then drag it into Calibre, which took care of the DRM for me with not even a notification.  Perfect.

I finished a book I had been reading, then read an entire book on it Saturday, and have started a third.  At this point I have to concur with the guys at Tested.com - Amazon is always improving their product, but at this point, I don't know what they could even improve on the Paperwhite.  Sure, the page turns are not instantaneous, but they're plenty fast.  The backlight is perfect.  The battery life is extreme already.  It's very, very light.  Unless they come out with color eInk, I think they may have perfected the ebook reader.

Monday, March 11, 2013

New thing: bike battery case

Wow, I really spent some time on this one (about 6 hours).  I'm pretty happy with it though and I hope it helps some people.  I've wanted to do this one for several weeks now and I was home sick today so...

One thing that's particularly cool about this is the new function that I used in OpenSCAD, "minkowski".  To create the basic case, first I modeled the battery to fit inside it, then I just used minkowski with that and a 3mm sphere, which created an object 3mm on all sides larger than the battery, with rounded corners.  Then I subtracted out the battery model to hollow out the case.  The other junk, the strain relief, velcro strap holder and screw holes and the alignment rails were added.

Once I had the whole object created as a single unit, I subtracted out a cube near the top to create the main body without the lid, then subtracted THAT from the whole thing again to create just the lid.

Thing 60776, Bike light LiIon battery pack holder

Saturday, March 9, 2013

Team 1502 "Technical Difficulties" cart sign

One of the guys on our FRC team asked me to make an LED sign for their cart, and I didn't want to go halfway...

Yes, I really put far too much time into this.  But at least half of that was because I was screwing stuff up, and that's how we learn, isn't it?

I published the design files on Thingiverse: http://www.thingiverse.com/thing:59585

Friday, March 8, 2013

Successful iPhone 4 screen replacement

One of the kids in our FRC Robotics group broke his iPhone 4 screen but good:
I bought a $30 replacement screen off eBay which came with tools.  Unfortunately on the first go I screwed up one of the cables on the digitizer so I had to order another.  Even though I'm doing this as a favor (and to learn a new thing, which I try to do whenever possible), it was my fault so I'll pay for the broken screen.

This is an iPhone 4 and the screen replacement is a bit of a pain in the neck.  Other models are easier.

FWIW you really should print out a disassembly guide such as the one you see taped to my desk there - it has a place to put every screw and part that is removed.  I taped down every screw to the picture of it on the paper as I disassembled it.  There are about 30 screws and many pieces to disconnect.

I recommend the iCracked screen replacement guide on YouTube.  Had I used that one the first time I would not have damaged the connector as they are quite thorough and tell you exactly what you have to be careful of at every step.

Anyway, after the 2nd screen arrived today it went together without incident.  It was, all told, about a 2 hour job for me.  Even though I saw some bad reviews for some screens, this one seems to look just fine to me, the digitizer seems accurate when I was typing on the virtual keyboard, etc.  I think I have everything working - the wifi, phone signal, vibrator, microphone, speaker, home button, volume and power buttons and both cameras are working.  And I don't have any leftover parts.

I'd say if you think you have a shot at this and are willing to take the time to be meticulous, it's probably achievable.  The other iPhone models are apparently easier, the iPhone 5 FAR easier (IE it's a 5 minute, 2 screw job).  The biggest problem was getting all the crushed glass out of the thing.


Wednesday, March 6, 2013

Quick and cheap ATMega USB devices

Project Ourobouros (link) is a neat project. Reflashing a USBasp Atmel programmer to use it for other purposes.  Gives you an ATMega8 cpu with some I/O broken out on a dongle sized PCB and a USB interface for $6 shipped.

Gotta try this.  Yet another thing on the list.

Tuesday, March 5, 2013

Bicycle taillight comparison

Cyclists, particularly commuters like myself, and most particularly ones that ride in the winter, tend to have a fascination with lighting.  I've owned a few taillights from the simplest department store blinkie to a Dinotte 140R.

[See update at bottom of article]

Currently my everyday light is a Magicshine MJ-818 which uses a 7.2 volt external LiIon pack, generally most people run it from the same pack they run their headlight from. If you already have a MagicShine headlight, the taillight with a Y power adaptor comes in at $30 and is absolutely unbeatable at that price.

For years, the standard self contained blinkie was the Planet Bike SuperFlash, and it's still respectable, but lately it has had competition and I believe at this point it's probably better for most people to look elsewhere.  The Superflash costs $20 (there's a turbo version for $30, but is still only 1 watt and others are more powerful for right around the same price).  Also the Superflash is known to not be completely waterproof and if run with alkaline AAA cells, not as environmentally friendly as it could be.

Especially good is that many lights now are USB rechargable with very long lasting LiIon batteries.  I've seen many cyclists out at night with nearly dead batteries.  With rechargable lights you never need be tempted to get that one last ride out of a set of batteries; just charge them up when they're getting low.  USB recharging is good because almost everyone already has some way to charge via USB so you don't have to keep track of yet another charger, and not producing and shipping (and ultimately, throwing away) another charger is good for the environment.

Lately the Cygolite Hotshot has been touted as the best cheap light.  At about $30 street it's pretty good.  However, it's very "spotty" and even 10 degrees off center the beam drops off considerably.  It is USB rechargable (via a mini-USB cable) and has an interesting ability to program the speed of its various flash modes to suit the rider.

The new contender that I'm playing with is the Knog Blinder 4V.  I just bought a road bike and wanted something that would be lightweight yet powerful, and would look nice on my bike.  The 4V fits the bill and surprisingly may be my favorite light right now, perhaps even beating out the Magicshine.  It's just a bit more expensive than the other small blinkies at about $35 street price.

When viewed from directly behind:
Magicshine is by far the brightest.  The Hotshot is next with quite a lot of light for such a little thing.  The Knog is a little less bright, and the Superflash is a distant fourth.

When viewed at a slight angle (say 15 degrees, IMO the most important viewing angle since many cars will be to the side a bit, and lights are often not mounted exactly straight):
The Magicshine is still pretty bright.  The Knog is just as bright as from directly behind and is close to as bright as the Magicshine.  The Hotshot has dropped off considerably and is not as bright as the Knog.  The Superflash has dropped off and is really not that bright at this point.

When viewed at a steep angle (45+ degrees to either side)
The Knog is the brightest, up to about 70 degrees to one side (140 degree spread) it's pretty much as bright as it is head on.  The Magicshine is still OK, not quite as attention getting as the Knog.  The Hotshot has dropped off badly at this point and the Superflash really isn't much worse here than at a lesser angle.

Here's a comparison with the lights bouncing off a white garage door.


Here's a comparison with direct viewing.

TL;DR - the Knog Blinder 4V is a winner.  It is thin, it's USB rechargable, it looks great even on a road bike.  It has a nearly totally flat field, showing just as much light out to the sides as directly behind it, and it's plenty bright in that range.  It also has a range of blink modes that should satisfy most people.

The downside: It's seat post mount, and would be cumbersome to mount some other way.  It needs to have some kind of seat post sized tube to wrap around, so if your seat post is hidden behind bags and you're not able to provide some other kind of thing for it to wrap around, you'll probably have to look elsewhere.  It'd be nifty if Knog produced some alternate mounts such as a seatstay, reflector bracket or rack mount.

Another downside is the somewhat odd charging connector - it plugs in just like a thumb drive which is great but on some computers you may need to purchase a USB extension cable to plug it in properly.  It just plugged into my PC just fine.

[UPDATE] - The Blinder 4V battery life is relatively short on all modes but eco-flash.  This is not too surprising given how bright the light is, but for me, the light barely makes a week in the "organic flash" mode that I like.  I'm used to charging my other taillights about once a month.  This isn't a huge problem but keep it in mind - I was caught at the beginning of a ride with a dead light,which is better than having it just go out in mid-ride.

Monday, March 4, 2013

Nano surgery

Last weekend I blew out a couple of Arduino Nanos while working on a project.  At first I tossed them in the trash, but then I thought better of it.  I ordered a few ATMega328 in the QFP package and was successful in fixing the nanos at a cost of about $3.50 each and about 10 minutes.
First, I put the board on a firm surface and used a box cutter knife to cut the leads close to the package (since I don't have a hot air rework station yet):

 This is the result
Then I used solder wick to clean up the excess solder, put a little liquid flux on the pins and pads with a flux pen, placed the chip on and drag soldered it down.

Finally, once the chip was in place, I soldered the 6 pin ICSP header in, connected it to another Arduino programmed to act as an ICSP programmer, and used the Arduino environment to burn the Arduino bootloader onto the new chip.

It works just fine.