Tracking individual battery voltages

Posted on October 16, 2011 by Jay

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.

Emily Smithson broken link recommendation spam

Posted on October 15, 2011 by Jay

I received two emails from “Emily Smithson” alerting me to broken links on a webpage I maintain. She recommended a website which has “mirrored” the original content as a place to link to.

How helpful, I thought, reading the first email. But then I saw that the 2nd email had the exact same format, almost as if it was sent out automatically by a spam bot. Continue reading →

Ferrofluid Sculpture – test 1

Posted on September 27, 2011 by Jay

Test 1 was not a failure. A Failure would have involved getting ferrofluid all over my clothes and/or workspace. However, I was not able to get enough ferrofluid to “stick” to the magnetic mount to get the weight up to the 74g needed for proper hovering action. Gravity pulled the ferrofluid down to the bottom of the screws and it started to drip off much too soon. It looks like I will have to augment the upper magnet with magnets on the lower parts to get the ferrofluid to surround the hovering part of the sculpture.

ferrofluid-test1

Ubuntu 10.04 AMD Radeon M6 chipset and Extron Electronics video multiplexer

Posted on September 23, 2011 by Jay

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.

Adding range to a Dakota Alert WMT-3000 wireless driveway alarm

Posted on August 15, 2011 by Jay

This is a photo of the radio transmitter inside of a Dakota Alert WMT-3000 wireless driveway alarm system. The wire coming through the hole drilled in the bottom of the case and soldered to the base of the antenna extends out to a 27″ wire whip antenna. Note the jumper circled in yellow. This jumper has a “high” and “low” setting. It is set to the “low” setting by the factory, and the “high” pin has been cut off. I found that the range was extended by soldering the “high” (cut off) pin to the center pin.

NetMedia iViewHD 2M POE Camera Review with ZoneMinder

Posted on July 31, 2011 by Jay

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.

Continue reading →

New voltage gauges

Posted on June 8, 2011 by Jay

This picture shows off my new flush-mount laser cut panel with voltage meters installed. These new gauges are Datel self-powered LED voltage displays (DMS-20PC-8-DCM for the red traction pack display and DMS-20PC-0-DCM-B for the blue accessory battery display). They are considerably more expensive than my previous gauges ($50 for the red and $59 for the blue) but have two major advantages. First, they actually fit inside the dash, so I can flush mount them instead of building a box around them. Second, they are “self-powered”, which really means they have their own DC/DC converter built in and draw power from the source they are monitoring. But, because each gauge has it’s own DC/DC converter, they are completely isolated from each other (something that my previous “isolated” DC/DC converter didn’t really do well.) Having all the power circuitry integrated into the gauge also greatly simplifies the wiring.

The gauges come with metal clips to fix them to the back of a panel, but the clips were too big for my opening. I improvised with a very close fit on the cutouts and some large rubber bands. If I ever need to replace the rubber bands, I just unscrew the four 6x 5/8 inch screws to remove the panel. (The screws are not exactly balanced on the panel as I was matching up to pre-existing holes.)

I wanted two different colors for the accessory and traction pack voltage, so I paid $9 extra to buy the blue LEDs for the 12 volt accessory battery. It turns out that this was a mistake. The blue gauge is much brighter than the red one, and at night it is blinding. I wired up a toggle switch to allow the driver to turn it off when driving at night. (The red gauge is just right, easily visible in the daytime but not too bright at night.) If anybody wants to buy a blue self powered voltage gauge for $50 including shipping I’d gladly sell it and buy a red replacement.

Jameco potentiometer grab bag

Posted on June 6, 2011 by Jay

So, if you purchase a few Jameco grab bags of potentiometers, what exactly do you get?

100 – 10 Ohms a good number, plus a few 20 ohms
500 – 50 ohms, a good number
101 – 100 ohms, a slightly smaller amount
201 – 200 ohms, a good number
501 – 500 ohms, a metric boatload (filled up 2 squares in my organizer)
102 – 1K ohm, a large number
202 – 2K ohm, a large number
502 – 5K ohm, two
103 – 10K ohm, three
203 – 20K ohm, eight
503 – 50K ohm, two
104 – 100K ohm, two
204 – 200K ohm, one
304 – 300K ohm, five screw pots, plus six larger slider pots
504 – 500K ohm, a large number
105 – 1 M Ohm, five
205 – 2 M Ohm, seven

Of course, if you wait a few months, Jameco’s overstock may be completely different and their grab bags may have completely different distribution of potentiometers.

On-Dash voltage guages

Posted on May 15, 2011 by Jay

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.
Continue reading →

HOWTO: Full Disk encryption on Ubuntu 10.04

Posted on March 26, 2011 by Jay

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”.