GPS temporal displacement

Everybody uses GPS.
We already know that the positioning provided has an error, usually in the range of 4 to 10 meters.
That's about space, but what about time?
By using Torque we can estimate it.
Torque log files contains GPS coordinates and the speed calculated from GPS readings: we can try to relate it to the speed reading from OBD, that is instantaneous, while the GPS speed is subjected to the delay induced by the GPS itself.
From the chart, we can say that the OBD speed is accurate, but the GPS value is delayed by an interval between 1 and 2 seconds.


Checking the 12V battery of the Yaris Hybrid without opening the back seat

The 12V battery of the Yaris Hybrid is located in a not-so-easy to access place, so a easier way to check battery health may come handy.

Newer versions of the Yaris Hybrid seem to have a jump start socket in the fuse box under the hood, on the driver's side.
I was wondering if the old ones may use the same trick.
My fuse box has a bolt where newer ones have the socket

so I just checked with a voltmeter and I saw that it carries the same voltage of the back seat battery.
Readings are the same as measured directly at the battery clamps.

So battery voltage can be measured from the engine hood instead of opening the back seat.


Motorola Defy vs Samsung S2 Plus

I've been using a Motorola Defy for the past 2 and a half years.
Now I switched to a Samsung S2 plus, expecting to find some improvements.
The S2 has a bigger screen than the Defy, but a lower resolution. Anyway I like the bigger screen more than the lack of resolution, that is not dramatic.
The AMOLED screen is way easier to read in sunlight, but contrast and gamma seems out of range: reds are loaded and dark photos are darker than on the Defy.
Current Samsung firmware doesn't have color calibration either.
With some gamma correction, this screen could kick asses.
With a bigger screen I would have expected a better on screen keyboard experience, but typing on the screen is a pain as always.
The battery is another notable difference from the Defy. It just drain faster on the S2. 
Way faster.
I never had to charge the Defy in the middle of the day. I wish I could say the same of the S2 Plus.
I don't know if it's a hardware issue or a software setting, but I have the clear feeling that the lower part of the screen is less sensitive.
The Defy was resistant to water and dust. The S2 clearly is not. This is something that I miss.
The S2 has double the RAM and double the cores of the old Defy.
This makes the S2 more responsive, but I expected a little more: there are still some apps that force the launcher to be reloaded, like dolphin browser.
The GPS gets a fix in a handful of seconds, probably thanks to the glonass system, but the compass is always wrong.
Even after calibration. This makes using Google sky really frustrating.
In the end, while the S2 plus is a good phone, I still think that the Defy, at its time was a notable terminal. An updated Defy would be a clear winner for Motorola.


Speed and Charge

How much current can you get from speed?
In the following graph:

  • speed is in blue, left vertical axis
  • RPMs in red, right axis, useful to check when the engine stops beeing dragged.
  • change current in yellow, left axis, negative values are indicative of recharge.

I drove a straigh, plain road up to 76 km/h and then I left the accelerator pedal alone, to let the car loose speed until 46 km/h (see the blue line decreasing over time)

The engine continued to spin without burning any fuel, then at 66 km/h it stopped (see the sudden break in the red line).

Charging current is not steady, it follows the speed, but not linearly (check the yellow line, lower values mean higher charge).

A graph of current values by speed shows a pattern:

Higher current values are in the lower part of the graph.

The higher recharge effect is at 66 km/h with 24A.

That is precisely the speed where the engine stopped, but neighbouring values vary widely.

The slope returns to a linear behavior at 62 km/h with 22A.

So, if you're going to drive down a hill and you want to maximize your recharge, it's better to drive at 60 km/h rather than 70.


Android Activity Recognition Battery Usage

I'm using an amazing android app called AutomateIt.
It's kind of a scheduler on steroids: it can execute actions based on triggers like time, position, connection status.
The latest release added support for "activity recognition": the phone should be able to tell if you're walking, driving, or standing still.
I defined a rule that turns on Bluetooth while I'm driving, so I can use my car hands free system.
It actually works, but at what price?
Here are the effect on a Samsung Galaxy S2 Plus.
This a night with an activity recognition rule defined: check the last hours in the graph: battery depletes at a rate of 1% every 4 hours.

Here is a night without any activity recognition: a 1% of battery juice lasts for 5 hours.

It seems that using activity recognition shorten you battery running time by 20%.