Category Archives: Technology

Posts that relate to technology. Reviews, HOWTO’s, problems & solutions.

Tracking individual battery voltages

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Line graph that shows the voltage of six batteries dropping under load. All six batteries follow the same deep V pattern, staying within 0.1 volt of each other.

This graph shows the voltage (multiplied by 10, so 65=6.5 volts, and 50 = 5.0 volts) batteries 1-6 of my electric pickup while accelerating. My first battery (blue) is consistently 0.1 volt below the others, so I am keeping an eye on it. But this graph shows that although it is a 1/10th of a volt lower, it does not sink lower than the other batteries under load, so it appears to be holding up well so far.

The graph also shows off my new (to me) Pak Trakr system. The Pak Trakr system connects to each battery in your pack with small remotes that daisy chain together. Each remote monitors six batteries and transmits the voltage levels once a second to a display and optional serial data logger.


Ubuntu 10.04 AMD Radeon M6 chipset and Extron Electronics video multiplexer

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After working perfectly for 4.5 weeks with the same podium setup, my Thinkpad X31 laptop refused to output VGA video to the Extron Electronics video multiplexer box at school.
It appears that the Extron Electronics box is not sending out proper Extended Display Identification Data (edid) which tells the laptop what resolutions it supports. My xrandr command finds the data for my laptop video display screen, but not for the VGA-0 port:

VGA-0 connected (normal left inverted right x axis y axis)
LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0*+   60.0
   800x600        60.3     59.9
   640x480        59.9     59.4

I have no idea why this started today. I don’t remember applying any patches to X-org in the last two days, and the technicians in charge of the podium swear that they didn’t change out anything.

I figured out a fix to make it (mostly) work. Tell xrandr to go ahead and force the VGA-0 port to a specific resolution with the following command:

 xrandr --addmode VGA-0 1024x768

This mostly works, but the sync signal is slightly off, leaving a black bar of 20-30 pixels on the left side of the screen. It is also annoying to have to run that command every time I want to display to the podium.

NetMedia iViewHD 2M POE Camera Review with ZoneMinder

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Small silver camera
I have recently purchased a NetMedia iViewHD 2M power over Ethernet (POE) camera (retail price $105) for use with ZoneMinder.

This small camera must be hard-wired into a switch that provides power over Ethernet (which will cost another $80-100, but allows you to power up to 4 POE devices). I bought mine used, and don’t plan on buying more. The one I bought would reset to factory defaults (requiring you to upload a new “website”) every few months, and after a year of use it died completely (won’t respond to DHCP address assignments). At used prices the NetMedia iViewHD 2M could be a good deal for daytime shots, despite my nighttime image quality complaints below, if the one you buy lives longer than mine, but I can’t recommend it.

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On-Dash voltage guages

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I received a VWRAS2-D12-D9-SIP isolated DC/DC power adapter from Digikey and built an updated voltage gauge module with dual gauges (one for the 12 volt accessory pack, and one for the 120 volt traction pack). The gauges were slightly too large to fit inside the dash, so I built an enclosure out of craft plywood that sticks out flush with the bottom of the radio.
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HOWTO: Full Disk encryption on Ubuntu 10.04

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How to set up an entirely encrypted disk using Ubuntu 10.04 (LTS):

    Use the Alternative installer (text based) ISO image so that you have access to the LVM and Encrypted Disk options.
    Assuming you want to keep a windows partition or some other pre-existing partitions intact, you will have to manually partition things instead of using the guided partitioner, so select “manual”.

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S-10 Electric Pickup

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Side view of the Electric S-10 Pickup
Our new commuter vehicle (and my new toy) is a second-hand electric conversion S-10 pickup. We purchased it from the original converter after he had upgraded to a Ford Ranger EV.

It is powered by 20 six-volt lead acid (PbA) golf cart batteries wired in series, giving a nominal 120 volt system. Sixteen of the batteries are stored in boxes under the tilt-up pickup bed. The remaining four batteries are under the hood, where the radiator would be on an internal combustion engine (ICE) vehicle. It can be charged via either the QuickCharge 120V charger plugged into a standard 15Amp outlet (which takes 13 hours) or the Zivan NG3 high frequency 240V charger (which takes 7 hours and a 240 volt outlet).

16 six volt batteries under the tilt-bed of the pickup
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Motorola Backflip Android 2.1 upgrade

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I have been using my HTC Aria as my primary phone, and using CyanogenMod it runs android 2.2. Instead of leaving it sitting in a box, I decided I wanted to use my backup phone (a Motorola Backflip) as a wifi network camera. However, it runs Android 1.5, which isn’t supported by the Free IP Webcam software. Luckily, Motorola has released an upgrade for the Backflip, if you know where to look. Continue reading →

Best AT&T DSL modem for difficult conditons: 2Wire 2701

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We recently moved to a new house that is far from the central office, and apparently is served by some very old copper. AT&T’s computer system refused to sell us any DSL plans faster than 1.5 Mb/sec, as the lines wouldn’t support any faster speed.

I have tried using three different DSL modems at this house. In order of age and success:

  1. Westell WireSpeed (2200) B90 DSL modem – This modem works at the full 1.5 Mb/sec speed, for a few hours. Then it gets slower and slower, until it averages 7KB/sec for downloads. (Uploads remaind at full 0.3 MB/sec speed). Power cycling the DSL modem fixes the issue and restores full speed for 12 hours or so.
  2. Motorola Netopia DSL modem – This modem occasionally was able to get full download speeds, but typically would max out at 0.3 MB/sec (30 KB/sec) for the download speeds. (Uploads remained at a full 0.3 MB/sec.) Power cycling the modem did not improve things.
  3. 2Wire 2701hg-B DSL modem with integrated wifi. This modem was able to maintain the full 1.5 MB/sec download speeds. Perhaps because it is the newest of the three modems, and has a better DSL chipset.

It was worth purchasing a new DSL modem for this house. (Although the Netopia and WireSpeed modems have both worked fine in other locations.)

Backflip wifi tether with Ubuntu Linux

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After gaining root access on my Motorola Backflip phone, I was (eventually) able to get wifi tethering working using the Barnacle application (version 0.5.1).

In Barnacle, I have “skip wpa_supplicant” checked, the channel set to six (6), and DHCP set up to use the OpenDNS DNS server (208.67.222.222) although the DNS server option may not be needed. (I had to also manually specify the DNS server IP on my client anyways.)

I had to pull some tricks on the client side (Ubuntu Linux) to make everything work. Specifically, setting MTU size to 1250 and setting up my own DNS name server IP.
The script I use to make this all work with ad-hoc networking on Ubuntu is as follows: Continue reading →

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

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Main application screen, showing the book "Postmistress" having 610 people wishing for it. 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.)
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