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Cheap USB analog interface?

Discussion in 'Electronic Design' started by Don Lancaster, Jul 2, 2011.

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  1. For years, I've had this ISOPOD back burner project going. The concept
    was a tennis ball shaped object you could ( reasonably safely ) clamp on
    one of your input ac power lines and it would transmit your current (
    and thus more or less your power ) consumption on a sampled-fairly-often
    basis.

    I'm wondering if a demo cannot be built up using stock parts at
    reasonable costs. The Fluke i2500 looks like a good (but pricey) front end.

    Question: What is a reasonably cheap analog to wireless USB stock
    product? Or preferably stock analog to wireless to web? Can it be
    powered from a current transformer? What reception software would be
    involved? Can javaScript on the web do it?

    The whole point is that smart power meters seem slow coming locally,
    and that many smart meters will be "closed' rather than "open access"
    devices. Some means is needed to safely sample power consumption for
    energy awareness. Without needing an electrician or meeting specs. Two
    units would likely be needed, one for each 110 volt arm of the 220 volt
    input.

    Yes, the sensor might be ahead of the meter. But the total power
    "stolen" would be miniscule and the utility benefits would be major.

    If the data rate was high enough, power factor could also be sensed.
    Even without, the current consumption should be a most useful metric.

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  2. Define cheap ;)

    www.microdaq.com The HoBo stuff does usb wireless.

    I have not seen a small ADC --> USB logger that's cheap. Would be
    useful tho.
    I've done a PIC USB HID and its not that difficult.

    Cheers
     
  3. That would require a TPC/IP stack, or maybe just UDP.

    Here's a Dataq logger for $29
    <http://www.dataq.com/products/startkit/di145.html#ordernow>
    You just need a wireless interface.

    Cheers
     

  4. What National Instruments is not.

    --
    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: http://www.tinaja.com/whtnu.xml email:

    Please visit my GURU's LAIR web site at http://www.tinaja.com
     
  5. hamilton

    hamilton Guest

    Its kind of funny that a few years ago, Wireless USB was the rage.

    Today the usb.org has changed the Wireless USB to a "good idea":
    http://www.usb.org/developers/wusb/

    PCs have Bluetooth or 802.11 as standard wireless interfaces.

    802.15.4 (Zigbee) seems to be a custom solution, but lots of people are
    making them.

    So, there is really no wireless standard that's cheap.

    hamilton
     
  6. hamilton

    hamilton Guest

    The cheapest wireless "standard" interface would be Zigbee.
    A serial Zigbee interface is <$20.
    I have played with:
    http://www.sparkfun.com/products/10253

    I was able to send messages over 20 feet indoors.
    PCs can only connect to one of these devices at a time though.

    The TI parts should be able to connect in a network, so many devices
    should be able to communicate with the host.

    I have not found any projects out there that have used these parts,
    however there are other projects using wireless networks.

    A quick google search found:
    http://en.wikipedia.org/wiki/Sensor_node

    Mesh networking may be a good way to get low power remote data logging.

    hamilton
     
  7. This $29 microchip module looks intriguing
    <http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en548014>

    400 meter range. I'm guessing 802.11 b

    Cheers
     
  8. mike

    mike Guest

    By far, the cheapest/easiest solution is to buy a BlueLine wireless
    power monitor...or one of the clones from Black&Decker etc.
    Cost about $25 on ebay or $15 at garage sales/swapmeets.
    It watches the wheel go around or the blinking light on digital meters.
    They also have a computer interface, but it's substantially more money.

    If you have a digital meter with a light, it's trivial to write a program
    for a 25-cent PalmIII to watch the light and log/graph the data.
    I'd planned to update the code to a newer palm with bluetooth
    for wirelessness. But, I found that, after a few days of monitoring,
    the new wears off and the desire for fancier features wanes.

    Once you figger out where the power is going, you do what you can
    to mitigate it and you're done.
    Doesn't do much good to monitor it if there's nothing more you're
    willing to do about it.
    You don't need data to know to take shorter showers or turn down the heat.

    The blueline tells you what you need to know and has some resale
    value when you're done.
     
  9. mike

    mike Guest

    problem with a killawatt is that you measure what you can plug in.
    The things that take the most power are hard wired, or 220V split
    across 2 phases...at least in the good ole USA.

    But the metrology problem is the same. If you aren't using it,
    turn it off. If you're not willing to turn it off, it don't
    matter how much instantaneous power is being monitored, databased,
    graphed, displayed, studied...just don't matter if you ain't
    gonna take some action.

    I try not to ask questions if the/my future is independent of the answer.
     
  10. mike

    mike Guest

    Yes, but you can determine that in any number of ways.
    A KillAWatt is a great tool to have around for about a week.
    Once you determine
    consumption, you don't need to track it continuously.

    I think I spend more for batteries for all my power and temperature
    monitors than I save by having current data.

    My VCR clock resets on power outage, so I pay the price to leave it
    running...at least in fall when there's something on tv to watch.
    Haven't done Energy Star since '94, but from what I'm reading that's
    changing
    big-time. Third party certification is/will soon be required.
    That's gonna make the costs go WAY up. So we pay for increased product
    price to get the piece of paper that confirms less energy use. Can't win...

    There's a lot you can do to minimize energy usage.
    Problem is that most people don't want to live like wilderness campers
    to do it.

    When you're paying $70/month for the ability to tweet your every emotion
    while driving the SUV to get to that $200 "gaga" concert,
    it seems pointless to shave a minute off your shower.
     
  11. hamilton

    hamilton Guest

  12. mike

    mike Guest

    True, but the objective is to save MONEY.
    The cost of a gas water heater plus the cost of getting the
    gas to the location plus bringing the whole installation up
    to current code, plus the permits plus the ...plus...plus
    and based on my water usage, I'd be dead before it paid back.

    I use the shower example because it's so wasteful and
    something everybody can relate to.
    Last time I did the math, it cost me 13-cents to take a shower.
    I could cut that by 90% without sacrificing cleanliness.
    Heck, when I had a small RV, I'd take a shower every day
    and go a week on 18 gallons of water.

    But I LIKE standing under the hot water spray. I like it
    13-cents worth.
     
  13. mike

    mike Guest

    You sure about that?
    How long do you turn it off at a time?
    What's the thermal time constant of the water heater?
    My math says that, for a well-insulated heater,
    it makes no sense to turn it off unless you're goin' on
    vacation.

    Gas is the most expensive way to heat
     
  14. mike

    mike Guest

    Read it again.
    Nowhere did I use the word "I".
    I DID use the word "YOU".
    Look around you...
    I don't know anyone over age 8...besides me...who
    doesn't have at least one smart phone with EXPENSIVE
    data plan. Instant gratification is the norm.
    Saving a few bux on energy is WAY down the list for
    most of the population.
     
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