Data loggers...

245

Comments

  • GreenerPowerGreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    Re: Data loggers...

    Out of curiosity, are these 5 panels the same or from different vendors with similar volts/wattages ? The reason I ask is that PV is current source device and you mentioned to use a resistor as load i.e. you are measuring a single point on the PV's I-V curve at some temperature ? Nowadays, most use MPPT charge controller to track the maximum power point of the PV. To effectively compare them, you would need a varrying load or preferably a variable current-sink device to be able to at least sample points across the PV's I-V practical range per temperature.

    To add to MikeO comments on the parts/equipments needed. The USB-1208 has 8 12-bit ADC (for 25V, that 6mV per step), 16 digital I/O . To accomodate 10 analog inputs (maybe 15 if you need additional 5 for temp sensors or probes), you can use an analog multiplexer and use the digital I/O to control the multiplexer via software as which channel to sample. Use 100A/100mV shunts and the shunt amps MikeO suggested. These can be done within your budget. You'd need to develop software to control the analog mux and do the analog readings.

    By the way, there was a thread in this board that people try water mist/spray to cool the panels and some one commented the trade-off for the PV gain vs water mist/spray control is practically nill.

    Good luck.

    GP
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    They are all identical panels. Just different water cooling designs.


    If you can just give a example of the senors and data logger so I can start looking on ebay? Thanks a lot for your help!


    Also, I was going to try the misting idea, but did not like that since you would have to use distilled water, or there is calcium build up.
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    And can some one please explain the following;

    How do shunt volts work?
    How do you measure them?
    Is there any equations that go with them to get it up to regular volts/ current?
    Do you need special equipment?
    Thanks.
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Data loggers...
    What sensors do I use with his? And software?
    The analog to digital converter measure voltages, so you will need to build the current sensors that were suggested in previous posts using the TI parts. Research the net and you may be able to download drivers appropriate to using standard acquisition program such as MatLAB or others. This will take some effort and study on your part, remember you are saving 1000's of dollars.
  • BB.BB. Super Moderators, Administrators Posts: 31,085 admin
    Re: Data loggers...

    Here is a typical shunt (about $24 from our host):

    wind-sun_2100_4361831Deltec 100 amp, 100 millivolt current shunt
    AC or DC - common item for use with many battery monitors and amp meters

    You attach the heavy / current carrying cable to the two posts... One each.

    There is one or more flat bars between the posts that are calibrated / high current / low resistance resistors (you don't want the resistance to change with temperature).

    Using the old V=I*R:
    • R=V/I= 0.100 volts/100 Amps = 0.001 Ohms resistance for this "smaller" shunt
    Now, you would attach your "voltmeter" to the two small screws on the side and measure the voltage drop across the shunt:
    • I=V/R= 0.050 Volts / 0.001 Ohms = 50 amps
    Now, please note that the voltage terminal have the full current of the heavy gauge wiring... For Battery Monitors, they put the shunts on the negative side of the battery bank and negative ground the battery bus... So even if there is a "short" between the voltage monitoring leads and ground--there is not much current.

    Normally, for computer remote sense leads, we put fuses or resistors at the shunt point to protect the voltage sense wiring from any shorts (which can cause fires).

    Of course, you can use smaller power resistors or other temperature stable resistance element as a less expensive shunt and measure the voltage drop across it.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...
    mikeo wrote: »
    The analog to digital converter measure voltages, so you will need to build the current sensors that were suggested in previous posts using the TI parts. Research the net and you may be able to download drivers appropriate to using standard acquisition program such as MatLAB or others. This will take some effort and study on your part, remember you are saving 1000's of dollars.

    So I would have to create it? That seems like a lot of research/ work... Are you sure they don't make anything premade?

    Any way to make this where would I get the necessary parts?
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Data loggers...
    So I would have to create it? That seems like a lot of research/ work... Are you sure they don't make anything premade?

    Any way to make this where would I get the necessary parts?

    I think the problem is that there's not a good intersection of a budget under $600 and using off-the-shelf parts.

    For example, using off-the-shelf parts implementing a WEL solution, it would cost:

    $385 * 1 = $385 - WEL unit (OurCoolHouse)
    $10 * 5 = $50 - Temp sensors for panels
    $45 * 5 = $225 - VDIV10:1 10-to-1 Voltage Divider Module (Campbell Scientific)
    $23 * 5 = $115 - MS-TV 0-10 VDC to 1-wire network converter (iButtonLink)
    $0 * 5 = $0 - 75 watt precision resistors (supplied)

    Total = $775 (all List pricing)

    Nothing else needed - no computer, no software. No parts to buy or build - no circuits to design. No time and effort to figure out how to put it together. And all of the requirements are easily met (actually sampling frequency will be once every 60 sec.). Data storage is done at a remote server, charts and graphs are included, all very reliable and precise.

    Not yet down to the $600 budget, but it's close.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Data loggers...

    I thought further about how to most economically implement an off-the-shelf solution, and got the numbers down quite a bit.

    Later, Campbell Scientific responded to my inquiry, and thus I learned of voltage divider module availability.

    This gets cost down to $775 for off-the-shelf, no effort, etc. Not at $600 budget, but much closer.

    I updated my posting from last night with the details.

    Hope this helps.

    Best regards,

    Bill
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Data loggers...
    This gets cost down to $775 for off-the-shelf, no effort, etc. Not at $600 budget, but much closer.

    That may be the best solution, one could roll their own only a 200 or so dollars cheaper, but the effort wouldn't be worth it unless it was treated as a learning experience.
  • jeffkrusejeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: Data loggers...

    Why not use 5 different DMM's. The DMM's could be read by the computer. The DMM's would measure both V and Current (<10 or 15 Amps).

    How about this DMM http://www.amazon.com/Tekpower-Digital-Multimeter-Interface-DT9602R/dp/B000E2422G/ref=cm_cr_pr_sims_t
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Data loggers...

    Most DMM's have autopower off.

    I think the Wel is the best option.

    To roll your own, yea, upfront cost is low, but I spent 3 months writing software for my current system. I have 5 years with working with PLC's, so that help.
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...
    jeffkruse wrote: »
    Why not use 5 different DMM's. The DMM's could be read by the computer. The DMM's would measure both V and Current (<10 or 15 Amps).

    How about this DMM http://www.amazon.com/Tekpower-Digital-Multimeter-Interface-DT9602R/dp/B000E2422G/ref=cm_cr_pr_sims_t

    So that one will work??? Will it come with software to keep and graph data???????

    If so that will be amazing!
  • GreenerPowerGreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
    Re: Data loggers...
    So that one will work??? Will it come with software to keep and graph data???????
    That DMM can be put to measure either Volts or Amps, one at a time (via the manual dial), not both at the same time. You would need 10 of them - 5 sets to measure volts, 5 to measure amps (the test lead need to be plugged into a 10A input, different from the V/Ohm input and the dial set appropriately). Bill's suggestion sounds best without any software development effort.
    GP
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...
    a0128958 wrote: »
    I think the problem is that there's not a good intersection of a budget under $600 and using off-the-shelf parts.

    For example, using off-the-shelf parts implementing a WEL solution, it would cost:

    $385 * 1 = $385 - WEL unit (OurCoolHouse)
    $10 * 5 = $50 - Temp sensors for panels
    $45 * 5 = $225 - VDIV10:1 10-to-1 Voltage Divider Module (Campbell Scientific)
    $23 * 5 = $115 - MS-TV 0-10 VDC to 1-wire network converter (iButtonLink)
    $0 * 5 = $0 - 75 watt precision resistors (supplied)

    Total = $775 (all List pricing)

    Nothing else needed - no computer, no software. No parts to buy or build - no circuits to design. No time and effort to figure out how to put it together. And all of the requirements are easily met (actually sampling frequency will be once every 60 sec.). Data storage is done at a remote server, charts and graphs are included, all very reliable and precise.

    Not yet down to the $600 budget, but it's close.

    Best regards,

    Bill


    Wait... No computer? No software? How will I get the information to the server/ on to my computer then? Thanks very much for this.
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...
    That DMM can be put to measure either Volts or Amps, one at a time (via the manual dial), not both at the same time. You would need 10 of them - 5 sets to measure volts, 5 to measure amps (the test lead need to be plugged into a 10A input, different from the V/Ohm input and the dial set appropriately). Bill's suggestion sounds best without any software development effort.
    GP


    So to get them both at once I would need a single phase correct? Or at least a multi meter that it measures both at once? Is there a special word for that?
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Data loggers...

    Ok, thinking out load here.

    How accurate do you need your measurements. In theory, he could get away with using one meter per panel. The key is he is using a fix load, aka resistor. Using Ohm's Law, he could get all the info he needs.


    This meter will not work, from the manual:

    "Auto Power Off 15 minutes after stopping the switch, or no any operation for the press button, the meter automatically enters to power off mode."
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Data loggers...
    ... No computer? No software?

    How will I get the information to the server/ on to my computer then? ...

    Correct - no computer (for purposes of DAS) and no DAS s/w to install.

    The WEL is an Internet Appliance. Plug in a 9 VDC power transformer (I included it in the $385 price), plug in an Ethernet cable connected to your router, and you're done. The WEL unit will every 60 seconds send to a central server, via the Internet, your sensor data, and any arithmetically computed data (like your computed current measurements, which will all be Vx/Rx where x=panel and R=load)

    Any time you want, you can download the collected data to your computer. The data comes in an .xls format file.

    As an example, all of the sensor data you see here: http://welserver.com/WEL0043/ is being sent to a central server once a minute by my single WEL unit for my residence. And arithmetically computed data is also sent at the same time (i.e., solar kWh production throughout the day, heat pump KBTU/hr capacity, etc.)

    At any time during the month, and particularly after each month, I download the .xls file and save it for possible post collection analysis, and offline charting.

    Here's a couple page summary of how the WEL works, beyond my summary above.

    Hope this helps.

    Best regards,

    Bill
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    Are you allowed to customize the graphs and put it in a time frame of choice? I need to put these graphs on a presentations. Is there a way I can get the data, as in so I can put it in spreadsheets?
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Data loggers...
    Are you allowed to customize the graphs and put it in a time frame of choice?

    I need to put these graphs on a presentations. Is there a way I can get the data, as in so I can put it in spreadsheets?

    Yes - the X axis can be specified in minutes, hours, weeks, or months. It is also specified in number of pixels.

    Also, see a thread in Beginner Forum here I started a while back - it shows many examples of WEL-produced charts I copied into the thread postings. I use WEL-produced charts copied into PowerPoint presentations frequently too.

    Yes - see my prior posting. You can download all data, at any time, in .xls format. Data is stored in monthly files on the server. All Excel charts are of course easy to proceed with charting, graphing, etc. on the downloaded data.

    Best regards,

    Bill
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    WOW! Cool, I will probaly do this then, I will stretch my budget so it will fit this.
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    Do I have to use S-TV 0-10 VDC to 1-wire network converter (iButtonLink) or is there something cheaper? I dont really need the temperature feature on it, because its me understanding that the wel unit already has ports for that correct?
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    Also, is there cheaper voltage splitters I can use? That seems very expensive just for resistors...
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Data loggers...
    Do I have to use S-TV 0-10 VDC to 1-wire network converter (iButtonLink) or is there something cheaper?

    I dont really need the temperature feature on it, because its me understanding that the wel unit already has ports for that correct?

    No, you don't have to specifically use iButtonLink's MS-TV sensor. You can do a Google search to see if you can find something less expensive. I don't have experience with anything other than the MS-TV, nor do I know if something is available. Generically, you'd be looking for a 0-10 VDC analog-to-1-wire-technology device.

    With respect to temperature: The WEL unit supports any sensor that is 1-wire-technology. You connect a CAT5 (or equiv) cable to the WEL, and then in linear fashion connect 1-wire-technology sensors to the cable. I have about 25 sensors of various 'flavors' (temperature, RH and pulse counters) connected to my cable. It's on this cable you'd connect the MS-TV sensor.

    The MS-TV sensor is actually 2 sensors: temperature and voltage. The WEL will read both of them.

    The temperature readings from the MS-TV are not very accurate due to the temp sensor being embedded into the MS-TV's plastic housing. For more accurate temp readings, I recommend you separately connect up 5 temp sensors to the 1-wire cable (and ignore the MS-TV temp readings). I included the cost of separate temp sensors in my estimate posted yesterday. If you just need 'ball park' temp readings, then you can reduce your expenditures by about $50.

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Data loggers...
    Also, is there cheaper voltage splitters I can use? That seems very expensive just for resistors...

    Don't know. You'd have to go research this.

    I've just recently been exposed to Campbell Scientific instrument stuff. For the pricing I'm seeing I'd expect the stuff to be gold plated.

    There's no reason why you couldn't make your own resistive bridges. You can get the schematic from the tech sheet for the Campbell Scientific resistive bridge, and go purchase your own parts, solder it together, etc. You'd need to do it 5 times.

    If you do this, then subtract $225 from the budget. And if you decide you don't need accurate temperature readings, subtract another $50 from the budget, for a total reduction of $275. Now you're down to a WEL ($385) and 5 MS-TV units ($115), for a total of $500, plus parts to make 5 resistive bridges, plus accurate 75 W resistive loads, plus some misc BOS parts (CAT 5 cable, CAT 5 plugs, wire nuts, etc.).

    Best regards,

    Bill
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    Which kit comes with the 75 watt resistors?
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Data loggers...
    Which kit comes with the 75 watt resistors?

    Don't know. You said earlier you were supplying these from work (including having aluminum heat sinks).

    Best regards,

    Bill
  • silent wolfsilent wolf Solar Expert Posts: 92 ✭✭✭✭
    Re: Data loggers...

    Oh, ok. It just looked like it said that it was supplied, ok then!
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