Jay's Technical Talk » Useful Links

Adventures with a boost converter

Jay — Sat, 14 Jan 2012 03:24:38 +0000

A boost converter is a dynamic electronic circuit that can “boost” a lower voltage up to a higher voltage. Current is of course reduced in the process, but if you design it right you only lose 5-25% of the overall power. I am in the process of building one that will convert the approximately 70 volt nominal output provided by my solar panels into 125-140 volts that will charge my trucks batteries. I also plan on adding a bit of maximum power point tracking and battery charge regulation to the control logic, making it a MPPT solar boost converting charge controller. Why do I have all of these wires and parts scattered across the dining room table? Because the market does not sell what I need. (Believe me, I’ve looked.) So I have decided to build what I need.

Not being an electrical engineer, I probably won’t be able to get 95% efficiency out of my system, but so far I’ve measured 85-90% efficiency when doubling voltage. [Test 1: 23 volts in at 0.28A for 6.44 watts, 46 volts out at 0.12A for 5.52 watts means 0.92 watts loss = 0.92/6.44 = 0.142 or 14.2% losses. Test 2: 34.8 volts in at 0.35A for 12.18 watts, 72.3 volts out at 0.15A for 10.84 watts, or -1.335 watts loss, which is 10.9% losses.]

I’m still running things off of a (relatively) low voltage and current supply (two/three 12V 5AH batteries) while getting everything working, and only boosting up to 50-72 volts when testing.

I had the circuit up to 95 volts (max of 16 watts) on the output side, but I really want to optimize it for a voltage doubling, and you lose a good amount of efficiency when going higher than a 50% duty cycle.

I have also not been able to find a commercially available boost regulating control IC that works with 100 volt inputs and produces up to 200 volt outputs. One probably exists, but digikey doesn’t appear to have it. I’m solving this problem by programming my own using a PIC micro-controller. At least the programmable nature of my controller should also allow me to add the battery charging maximum voltage/current and solar panel MPPT logic into the system. I am currently working on a single phase boost converter, but the plan is for the final system to be two phase (which basically means that I use two of them in parallel). This means that I need my single phase system to be able to support 100-175 watts maximum. Soon I’ll be moving from my 25 watt resistive load (25 watt lightbulb) to a 100 watt resistive load. Eventually, I may even borrow a 75 volt power supply and test it up to 140 volts.

While working on my boost controller, I’ve found the following reference links very useful:

I have also made a few mistakes that people making their own boost converter may want to avoid:

Within reason, the higher the switching frequency the better. I started off using a PIC12F683 chip which only has a single PWM output. Because I was planning on building a two phase system, I decided to code my own PWM loop that would support two phases with a 180 degrees difference. (A fancy way of saying that they would each be ON for the same amount of time, but that while channel A’s ON time would start at the beginning of the period, channel B’s on time would END at the end of the period. If the duty cycle went above 50% they would overlap for a bit in the middle.) After spending an hour on my fancy 2 phase PWM system and testing it with some visible LED’s, I took all of the delays out of it only to find that my 8Mhz internal oscillator could only support a period of 1.5-3 kHz. Sure, it sort of worked, but you could HEAR it switch. It also required a much larger inductor for the same power. So, I switched over to using the built in PWM subsystem, which can easily hit 73 kHz while still having 5-6 bits of precision. I now plan on switching over to a PIC 16F chip which has a dual channel PWM that I THINK can do an 180 degree 2 phase signal in hardware (if I’m reading the specs correctly…)
Most MOSFETs require at least a 10 volt gate signal. If you switch them with a 5volt logic signal directly from the PIC they will switch (at least mine did), but they will not carry current without burning a lot of it up as heat. I was wasting 80% of my power as heat in the MOSFET until I wired up a transistor off of a 12V rail to amplify the signal to 12 volts. I plan on using a IXDN604PI gate driver chip for my final design.

Using the Microchip PIC Kit 1 with Linux

Jay — Sun, 01 Jan 2012 22:15:40 +0000

The PICKit 1 is a combination programmer and development board for midrange PIC micro-controllers. In addition to being able to program FLASH pic devices, it also allows them to run and access 8 (charlieplexed) LED’s, a pushbutton switch, and a potentiometer. It’s a great little board for learning the basic of micrcontroller programing, but unfortunately it is not supported by Microchip’s new MPLAB X software (that is written in Java, and supports Linux/Mac in addition to Windows).

You CAN however use the PICKit 1 under linux. The piclab software is supposed to support it (I have not tested this). I use version 1.6 of the PicKit1 flash usb programmer for unix. Even the newest 1.6 version reports checksum errors after writing the hex file, but it does work correctly.

To make it work as an external program in MPLABX I had to select the “format HEX file for download” option under the Linker so that it would not fill all 2048 flash bytes when the program was smaller than that. I am able to manually run the usb_pickit command after building to flash the code, but it’s kind of annoying, as that program has a problem verifying the checksum and reports an error every time (which is interpreted as a build failure) plus, I have to run mplab X with root permissions to be able to access my USB port.

Controlling the Cricut Personal (desktop cutter) via Linux

Jay — Tue, 25 Oct 2011 00:35:25 +0000

I caught a deal on cricut.com where they were selling their original “Cricuit Personal Cutter” (refurbished) for $49.99 ($65 with shipping). This seemed like a very good deal to me, so I bought one. By itself, the Cricuit can cut specific shapes and letters from paper (it includes a free set of shapes/letters, and you can purchase cartridges to add more). I plan on using it to cut metal foil (one of the few things you can’t cut with a laser cutter, because it is reflective) and potentially make stencils. I may also be able to use it as a plotter using special attachments for pens. (Circuit board resist markers anyone?)

To make full use of it, I wanted to be able to cut arbitrary paths from my material, which means controlling the Cricut from my computer. Luckily it comes with a built in USB port that is recognized as a standard serial port. Also luckily, other people have already figured out the command and control protocol and built a library to control it.

I found the directions on this page very useful getting libcutter working. So far I have simply use the draw_svg utility program that is included with libcutter to cut out vectors created in Inkscape.

PBS Wishing – Android App to find out if a book is popular!

Jay — Wed, 18 Aug 2010 11:44:20 +0000

I have developed an application for Android Phones (OS version 1.5 or higher) that allows you to enter an ISBN from a book (or scan the barcode if your phone has a camera) and find out how many people are wishing for the book on PaperbackSwap.com. If a lot of people are wishing for a book, it’s a good indication that the book is popular, which may mean it is worth reading. (Or at least, if you decide you don’t like it, it will be easy to get a book credit for it on paperbackswap.com.)

You can find it easily in the Android Market by searching for “Summet”, (or “PaperBackSwap”). Alternatively, if you already have a QR barcode scanner on your phone, you can take a picture of this QR code to go directly to it in the market:

Jay’s list of the Best Android apps

Jay — Sat, 17 Jul 2010 00:45:24 +0000

I’ve had my Motorola Backflip for a month and have settled on a set of applications to keep on my phone. All of these applications work with Android version 1.5. My Backflip has a Camera / GPS / Compass and Accelerometers. Where an application makes use any of these hardware components I’ve mentioned it in the description. If you think I’m missing a great one, let me know!

Internet Clients:

K-9 Mail – K-9 Dog Walkers
My IMAP email client. This is the application I use the most on the phone.
SSI gTasks ToDo – SSI
This application allows me to view/edit my Google Tasks list on my phone.
NewsRob (Pro) – Mariano Kamp
This RSS reader syncs with Google Reader, and is the only application that I have paid to upgrade to the “pro” version.
Meebo IM – meebo
An IM client that supports all the networks I use.

Multimedia:

museek Music Player – musicexplorer
I have several gigs of ogg vorbis music on my phone, and museek had the playlist support I needed.

Android/Cellular Enhancement:

Advanced Task Killer – ReChild
This program allows you to kill off certain applications to save memory.
Android Agenda Widget - Everybody All the Time
The most customizable way to quickly and easily display your calendar on the home screen as a widget.
Apps Organizer – Fabio Collini
As you can see from this page, I’ve got a LOT of applications. The default applications drawer just doesn’t cut it. Apps Organizer allows you to put applications into little windows by category and call them up quickly.
Google Voice – Google
If you use google voice for “visual voicemail” this application makes your transcripts easier to view than via SMS. It also integrates google voice calling with your dialer.
BatteryLife – CurveFish
A nice battery widget.
Battery Graph – Morgan H
This program tracks your battery voltage over time and plots the data on a graph.
System Panel – NextApp Inc
Allows you to see how much CPU (and Memory) each application is using. The paid version also records historical data.
DropBox – Dropbox, Inc
A free commercial product, DropBox makes it easy to keep files synced between your phone and various computers. I am impressed with their cross platform (linux) support.
GPS Status – EclipSim
A nice status monitoring program that gives you all kind of information about your internal GPS subsystem, satellites in view, signal strength, etc.

Reference Tools:

Easy Tie Lite – Basesign
Need to tie a Tie for a wedding or other formal occasion? This application will remind you how!
Unit Converter – Convert Pad – Sonny Moon
It’s unit conversions. I don’t use it much, but when you need it, it’s nice to have.
Periodic Table – PeriodicPad – Sonny Moon
I haven’t actually needed to look up information about an element yet, but should I ever need to do so, I’m ready!
SitOrSquat – Densebrain, Inc
A national directory of public bathrooms. Haven’t had to use it yet, but it sure seems like it might be useful to have!
Google Sky Map – Google
Google really did a skymap right. Your phone uses it’s GPS, compass and accelerometers to make the phone display the stars in the direction you are holding it.

AR / Internet Data Tools:

Barcode Scanner - Zxing Team
A barcode scanner that can link to online content. It works with 2D barcodes and can decode email/URL’s/phone numbers.
Shopper - Google
Looks up prices for books, movies, and CD’s. In addition to barcode scanning, it can also recognize cover art in some cases.
Zillow Real Estate – Zillow.com
Basically a layer of home prices overlaid on google maps.
Stock Quote – BlShlNews
An advanced stock portfolio tracker. Handles cost per share overall gain/loss calculations. Smaller text display than Quote Pro (below) but offers links to financial news/charts, etc, as well as a desktop widget. This is the best free stock tracking tool I’ve used, but if you want something a bit simpler, try out Quote Pro.
Quote Pro – Quirk Consulting
Keep an eye on your stocks with real-time tracking. Simple application with one-screen updates on your stocks of choice.
Trapster - Trapster.com
National database of police speed traps and radar cameras.
Google Translate – Google
Google powered translation system.

Tools:

Wifi Analyizer – farproc
Scans the WiFi bands and tells you what networks are nearby, and their signal strengths. Useful to find open (free) frequencies or to test your AP’s signal strength and coverage.
Ruler – Babak Mozaffari
An on-screen ruler that can be calibrated.
JogTracker – Highway North Interactive
GPS map logger that calculates speed, caleries, etc. Also includes ability to upload jog/walk/run/cycles to the jog tracker website.
Tuner – gStrings – cohortor.org
Use your phone as a instrument tuner.
Metal Detector – Kurt Radwanski
Uses your phone’s compass to detect metallic objects. More of a party trick than an actual useful metal detector, but I guess if you had to find an old V8 engine that was buried only a few inches under sand….
Crow’s Flight – GPS – Cw&t
GPS without the maps. Log a point, and it tells you the direction and distance back to the point.
Bubble Level - Antoine Vlaney
Uses your phone’s accelerometers to work as a level. May not be as accurate as a true carpenters level, but if you only had your phone….
Compass - Snaptic
The best interface to your phone’s internal compass. Some modes also integrate GPS data.
StopWatch - sportstracklive.com
A standard stop-watch application, but it also includes count-down timers and alarms.
BACKFLIP Light - Motorola Inc.
A Backflip specific application with one lightbulb shaped button. It allows you to toggle the Motorola Backflip’s LED flash on/off to use as a (quite powerful) flashlight.

Security:

Big Brother GPS – eGnarF
This application will wake up periodically and send GPS coordinates to a website of your choice. I like the fact that it sends the data to any website you want, and even wrote a simple script to take advantage of it. It’s not a stealth program, so perhaps not as good for securing your phone, but it can be used to allow others to see where you are, what routes you took, etc.
Lookout Mobile Security – Lookout
A (currently) free commercial product beta that includes virus scanning, phone GPS tracking, etc…
Wm Anti Theft Lite - Winkymega
A program that watches your SIM card. If somebody replaces your SIM card it will SMS you and a few other friends phone numbers with the new information so you can try and catch the person who stole your phone.

Hidden Roomba Diagnostic checks – Stuck Bumper Sensor

Jay — Mon, 17 May 2010 22:51:03 +0000

Roomba with stuck bumper sensor
The above video shows a roomba with a stuck front bumper sensor. As you can see, the robot keeps backing up and trying to turn away from
the phantom obstacle it thinks is in front of it. This particular sensor was triggering because lint had gotten into the optical beam path and was blocking light to the photodiode detector even when the bumper was not being hit. I was able to repair it by removing the bumper cover (unscrewing 4 screws) and vacuuming out the hole where the plastic pole from the bumper goes between the IR diode and photo-transistor.

I found the following website to be very useful when debugging the sensors on my Roomba to determine which of the front bump detectors were malfunctioning:
http://mysite.verizon.net/gsplews/Diagnositic-Tests_Proc.v.0.5.htm

Summary: Hold the spot and clean buttons down. Push the power switch. Keep holding spot and clean buttons down while the robot gives five ascending beeps, and five descending beeps. Release spot/clean and you are in diagnostic mode.

Test zero: Flash all leds
Press clean to advance to the next test.
Test one: Bumper Sensors
Test-Two: OUTER, CLIFF-SENSORS PAIR
Test-Three: INNER, CLIFF-SENSORS PAIR
Test-Four: WHEEL-DROP SWITCHES (3 ea) and WALL-SENSOR (1 ea)
Many other tests follow, but deal with motors, etc and can be dangerous if you let the robot run itself into something, because it will NOT automatically stop moving. Read the above linked page if you want to do any of the other tests.

Running Ventrilo under Wine in Ubuntu Linux

Jay — Sun, 11 Oct 2009 02:06:37 +0000

Wine will install and run the ventrilo VOIP client very well. To get this working, follow these steps:

apt-get install wine wine-dev msttcorefonts

download ventrilo-3.0.5-Windows-i386.exe

run “wincfg” to prepare things

run “wine ventrilo-3.0.5-Windows-i386.exe”
(go through the install, using all the defaults)

Now, everything works with one quirk.
Push to talk works only when the ventrilo window “has focus”
This is somewhat understandable, but annoying, in that you have
to focus the ventrilo window before you can talk.
The other option is to use voice-detection, but that takes up a bit more cpu-time, and you may accidentally broadcast something you don’t want to.

A program that listens for keypreses and directs them to the ventrilo window fixes this problem:

http://np1.pp.fi/ventriloctrl/

http://np1.pp.fi/ventriloctrl/ventriloctrl-0.3.tar.gz

To compile it, you’ll need xorg headers:
sudo apt-get install xorg-dev

Aiptek HyperPen T-6000U tablet with Ubuntu 9.04

Jay — Wed, 23 Sep 2009 01:17:16 +0000

Getting the Aiptek T-6000U tablet working with Ubuntu 9.04 was relatively easy, following the directions here.

Summary:
Install the xserver-xorg-input-aiptek package.
Add a file called 10-aiptek.fdi to the /etc/hal/fdi/policy directory containing:



  
    

      aiptek
      true 
      On
      stylus

      absolute

Moving NTFS paritions using Ubuntu (Vista, XP)

Jay — Sat, 15 Aug 2009 15:15:22 +0000

This guide gives a good step by step procedure for moving a windows partition from one drive to another:
http://ubuntuforums.org/showthread.php?p=7742172

If you get an “autochk.exe not found” error message just after windows XP boots, it probably means that you have the partition type set incorrectly. Using fdisk under linux just use the “T” option to change the partition type to NTFS (hex 0×07 or number 7 in fdisk).

Encrypted home partition for Ubuntu 9.04

Jay — Sat, 18 Jul 2009 19:59:43 +0000

Following the directions on Lars’ blog, I set up an encrypted home directory on Ubuntu 9.04 using LUKS.

The following commands were all executed with root permissions. Add “sudo” to the front of the commands if you are not running with root permissions.

apt-get install cryptsetup libpam-mount cryptsetup -c aes-cbc-essiv:sha256 -y -s 256 luksFormat /dev/sda7
The partition I used was /dev/sda7, replace that with the partition you created. It will ask you for a password, I suggest using the same password as your login.
Then, to map the encrypted partition to /dev/mapper/cryptohome, do this:
cryptsetup luksOpen /dev/sda7 cryptohome
Then create a (ext3) filesystem. You may substitute a file-system of your choice here, but ext3 is the most widely used, and therefore, tested.

mkfs.ext3 -j -m 1 -O dir_index,filetype,sparse_super /dev/mapper/cryptohome (-m 1 and sparse_super save space, and should be safe as this is not a root filesystem. Note that the O for options is capitalised, and you may NOT have spaces after the commas that separate the options.)

To test that everything is working, unmount it, try to mount it again and make sure you can write a file to the partition and unmount/close it!

cryptsetup luksClose cryptohome cryptsetup luksOpen /dev/sda7 cryptohome mkdir -p /mnt/test sudo mount /dev/mapper/cryptohome /mnt/test touch /mnt/test/testfile ls /mnt/test umount /mnt/test cryptsetup luksClose cryptohome

To make it mount automatically when you log in:
Make sure you do not have a partition listed for your home directory in /etc/fstab.

Add a line in /etc/crypttab:
cryptohome /dev/sda7 noauto luks

And configure pam_mount in /etc/security/pam_mount.conf.xml to auto-load your encrypted home directory on login:

Note that initially the users home directory will be owned by root, and you will have to chown -R on the home directory to make things stop complaining. Doublecheck that the “testfile” you created earlier is in the users home directory.

If you get an error message that says: pam_mount(pam_mount.c:100): unknown pam_mount option “use_first_pass” you can get rid of it by editing the /etc/pam.d/common-pammount and /etc/pam.d/common-auth files and removing the “use_first_pass” option from both of them.