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I have delusions of possibly making an embedded thermostat solution that tracks energy usage, inside and outside temperature and humidity and possibly online weather forecasts for setting house temperature.  For this to work, I need to fully understand thermostat wiring.  It took a bit of looking around the net to identify thermostat wire colors, thermostat terminals and functions, so I thought I would summarize it in a post.  Read the rest of this entry »

I received my boards from the DorkbotPDX group order. While the purple solder mask is umm, "interesting". The board quality is beautiful. This was the first SMD soldering I've ever done. I started with tinning the pads with my normal iron and normal solder. I wanted to try that and see how it compares with solder paste I'll use later. Then I put some tack flux on top of the solder with a syringe. Before I used the flux, I was able to blow the tiny LED I'm using off the board with my hot air iron. The LED stays on the board and remains when the flux melts, due to surface tension.
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I got a kick out of the Le Dominoux project for the 555 contest. I thought about making a few to mess around with. This would be a good project to practice some manual SMD soldering skills. I haven't worked with SMD at all. (Yes, I know that the Le Dominoux was through hole constructed, but I planned on mine being SMD.)
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The AVR ISP II is a device to program an AVR microcontroller using a 6 pin header in a circuit. It does not contain any capability to power the circuit being programmed. This could be very handy.

Dave Jones at the EEVBlog has a video about adding power to the ISP cable, using an LM317 to provide both 5V and 3.3V. The issue with this, as he stated, was that the 5V source was very close to the required dropout voltage of the regulator to get the 3.3V. In addition, resistors are needed to set the voltage. This is my version of hacking on the AVR ISP II.
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Precentral.net read through the initial TouchStone theory post I put up and asked HP about my theories. As they posted in this article on the site, HP confirmed the identification to work as I assumed.

The new TouchStones will use the 3.1 MHz frequency to pass a unique key to the new WebOS phones, which will enable them to know where it is docked. You will obviously have to tell the phone where each dock is located the first time you use it. Derek did a great job translating my geek speak into general WebOS fan digestible content.

Only a few errors with the wording in the document. He refers to a coil for each frequency. I believe that both frequencies will use the same coil. It is resonant on both the communication frequency (3.1 MHz) and the charging frequency (118.5 KHz), so there is no reason to add extra hardware to the mix. This isn't really important to the end user, but just trying to be technically correct.

Some have speculated that this 3.1 MHz frequency will allow the TouchStone to have a data USB cable. I don't think this is possible. The data rate on a 3.1 MHz carrier is very low. The best that could be emulated is an old style serial connection (think phone line modem speeds). Nothing even close to the speed of even USB 1.0. It will most likely only be a method of establishing the connection via Bluetooth for major data transfer. Otherwise, it will just be used to exchange fairly short messages, like the URL example shown during the Feb. 9th event.

When the Palm Pre was released, Palm also sold a unique inductive charger called the Touchstone. Inductive charging isn't new, by any means. Electric toothbrushes and many other devices have used them in the past. This was a first for cell phones, I believe.

When I purchased my Pre and eventually many Touchstones, I didn't have a good oscilloscope to play around with the signals. Now I do. With the announcement of HP's new phones and an expansion of the TouchStone coil functionality in the phone, I thought I would take a look.
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This is a picture of a capacitor from a Chinese company, after being cut open. Inside, it is just a small capacitor. There are two problems with this. First, capacitors are rated with two values: Working Voltage and Capacitance.  The most important is the working voltage. On the large cap, it is listed as 50V. Notice the smaller cap is 35V. When a capacitor is submitted to over voltage for a long period of time, the dielectrics (the insulator between the two sides of the capacitor) in the capacitor break down and it explodes. Yee-haw. The capacity issue is a little less troubling. You bought 6800uF, but were only given 2200uF. You got a capacitor that is 1/3 of what you thought it was. These are most commonly used in power supply filters and the device it is used in will be subject to the power line frequency hum, do to poor filtering. The business model on the company is genius. By capacitors, put them in a pretty case, sell for more money. A quick search shown retail cost of the small capacitor at about $1.50. The large one, near $3.00. Genius. Until power supply capacitors start exploding.