Electronics

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So Texas Instruments graciously bestowed upon me a free HawkBoard development platform. The board consists of TI’s OMAP L 138 device, which combines an ARM 9 core and their C674x Floating Point DSP. More info @ hawkboard.org. It is similar to the BeagleBoard, but with a different application processor. My problem is figuring out how to work with it and what to do with it. Any suggestions would be greatly appreciated!

My BatchPCB order for the V2.0 Arduemetry boards as well as my new XBee GPS module has arrived.  Take a look at the pictures below.  I quickly soldered up the GPS module and it looks and works great.  I think it gets better reception now that it is on its own board with a good ground plane.  Definitely seems better than before when I had just soldered pins to the module and plugged it into a socket on my V1.0 board. Now I just need to find the time to assemble the V2.0 board and test it out.  After that’s up and running I’ll have to think of what to do next with this project – possibly make some more modules (sensors, antenna connectors, etc.) with the XBee footprint.  Any suggestions?

XBee GPS Module PCBs

XBee GPS Module PCBs

XBee GPS Module Bottom

XBee GPS Module Bottom

XBee GPS Module Top

XBee GPS Module Top

Arduemetry V2.0 PCBs

Arduemetry V2.0 PCBs

Several months ago we signed up with ComEd’s Real-Time Pricing Program (RTPP). The way that works is that, instead of getting charged monthly for your electricity consumption based on a daily or monthly aveage rate, your meter computes your usage at the time of use (TOU). ComEd has different hourly rates during the day each day and your bill is compiled by applying these hourly rates to your TOU consumption. What’s nice about that is you can take advantage of cheaper rates at night by shifting some of your heavy demand activities (laundry, dishwasher, etc) to those nighttime hours. We’ve actually seen a nice decline in our bills by simply being aware of how and when we use our electricity.

To aid in power awareness, companies have developed such devices as the Kill-A-Watt and The Energy Detective. Also, ComEd posts the current hour’s and expected future hours’ rates on their website so you know when prices are high or low. This all gave me the idea to create something to increase awareness even more.

Imagine if you had a simple display or colored light in a common area of your house, such as the kitchen. If you are planning to do sone laundry or ironing or washing dishes or running your AC, you could look at this device and it would give you an instant snapshot of your current power situation. It would tell you how much absolute power you are pulling from the grid, how much the power company is currently/will be charging for said power, and what the resulting usage will cost you. This could be displayed with text on a screen or via a simple red-yellow-green light conceptually indicating the severity of your activities and current rates to your bill.

Several challenges exist in creating such an appliance. First, how do you monitor your usage? Our meter outputs a power consumption pulse (akin to the rate of spin on older disk meters) via an IR LED on the front face. That is one option, but then you have to string out a cable with an IR detector to the front of your meter. I’m not sure what ComEd would think of that if they came around to read or service the meter. That also brings up the question: just how do they read out and receive your TOU power consumption data? I was hoping it was based on something like Zigbee that I could possibly read wirelessly, bu after doing some investigation into my particular meter model, it doesn’t appear to have that feature. The other option is to use current clamps on your incoming lines like The Energy Detective system does.  That system is really nice in that regard, but it isn’t designed to account for the real-time pricing.  Second, you need to be able to pull down the current rates off the ComEd website.  This shouldn’t be too hard – you just need an ethernet interface on the box and then run some code to pull up and parse this page (it’s too bad they don’t have an XML feed as well).  Finally, you would want to put it all together into something that looks nice which can give you the information you need at a glance.  I like the idea of having a globe of some sort, kinda like the Ambient Orb, or like the Energy Joule which would change colors based on certain conditions (stock market, weather, etc.).  This way, you would just look at what color is on to give you an intuitive feeling about how you should be using your electricity.  Red would indicate high prices or high usage or some combination.  Yellow would mean you have high usage at low prices or low usage during times with high rates.  Green would indicate that you are using little power and that the rate is relatively low.  Everyone wants to “Go Green” these days, so the more you could maximize the green time of this device, your bill would be lower and so would your environmental impact.

I hope to accomplish the goal of creating such a device in the near future.  That is step one.  Step two is seeing how we are affected by its information, how we adjust our habits accordingly, and how it impacts our bill.

I’m currently working on a revision of the PCB to correct issues with the first version, notably

  • Lack of RC circuit on RESET/DTR line which prevents the Arduino IDE from properly resetting the MCU and loading new firmware. I was able to get around this with the V1.0 board by adding a resistor on the back side and putting a capacitor in series with the reset pin going to the FTDI adapter.
  • Changing the sockets for the GPS module. I had originally planned on just soldering pin headers onto the Inventeksys GPS module itself, but they were a weird spacing (1.9mm) and it didn’t work out so well.  The new design will replace the 10-pin 2mm headers with standard size XBee socket.  This will allow you to use an XBee or a (to be designed) GPS module board in either socket, one with hardware serial and one with software serial.
  • Adding LED(s) for GPS and XBee link status
  • Connecting GPS power control to MCU to enable power-saving functions
  • Other minor improvements including better RF coil for GPS antenna to improve sensitivity. Previous one had a low Q value at the L1 frequency and was self-resonant below that frequency.